Crafter.Review/implementations/Crafter.Review-Plan.cpp

// SPDX-License-Identifier: AGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®

module Crafter.Review:Plan_impl;
import :Plan;
import :Json;
import :Text;
import :Crypto;
import std;

namespace Crafter::Review::Plan {
    namespace {
        // The bytes of `p\d+:` at the start of a unit id, where \d is any
        // Unicode decimal digit, as re.match reads it.
        std::optional<std::size_t> PkPrefix(std::string_view id) {
            if (!id.starts_with('p')) return std::nullopt;
            const std::size_t digits = Dyn::DecimalRun(id, 1);
            if (digits == 0 || 1 + digits >= id.size() || id[1 + digits] != ':') return std::nullopt;
            return 2 + digits;
        }

        // group(1) of ^p\d+:(.+)#[^#]+$: the path between the prefix and the
        // last '#', which must have something after it. `.` stops at a
        // newline; [^#] does not.
        std::optional<std::string_view> FileOfUnit(std::string_view id) {
            const std::optional<std::size_t> prefix = PkPrefix(id);
            if (!prefix) return std::nullopt;
            const std::string_view rest = id.substr(*prefix);
            const std::size_t hash = rest.rfind('#');
            if (hash == std::string_view::npos || hash == 0 || hash + 1 >= rest.size()) return std::nullopt;
            const std::string_view path = rest.substr(0, hash);
            if (path.contains('\n')) return std::nullopt;
            return path;
        }

        bool IsHex(std::string_view text) {
            return !text.empty() && std::ranges::all_of(text, [](char c) { return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f'); });
        }

        // ^\d+\.\d+
        bool StartsWithVersion(std::string_view line) {
            const std::size_t major = Dyn::DecimalRun(line, 0);
            if (major == 0 || major >= line.size() || line[major] != '.') return false;
            return Dyn::DecimalRun(line, major + 1) > 0;
        }

        // ^(base-commit|prerequisite-patch-id): [0-9a-f]+$
        bool IsTailLine(std::string_view line) {
            for (const std::string_view head : {std::string_view("base-commit: "), std::string_view("prerequisite-patch-id: ")}) {
                if (line.starts_with(head) && IsHex(line.substr(head.size()))) return true;
            }
            return false;
        }

        // ^index [0-9a-f]+\.\.[0-9a-f]+( \d+)?$ -> group(1) ("" when absent)
        std::optional<std::string_view> IndexMode(std::string_view line) {
            if (!line.starts_with("index ")) return std::nullopt;
            const std::string_view rest = line.substr(6);
            const std::size_t dots = rest.find("..");
            if (dots == std::string_view::npos || !IsHex(rest.substr(0, dots))) return std::nullopt;
            const std::string_view after = rest.substr(dots + 2);
            const std::size_t space = after.find(' ');
            if (space == std::string_view::npos) {
                if (!IsHex(after)) return std::nullopt;
                return std::string_view();
            }
            if (!IsHex(after.substr(0, space))) return std::nullopt;
            const std::string_view mode = after.substr(space);
            if (mode.size() < 2 || Dyn::DecimalRun(mode, 1) != mode.size() - 1) return std::nullopt;
            return mode;
        }

        // \d+(?:,\d+)? at `at`: the bytes it takes, 0 for no match.
        std::size_t LineRange(std::string_view text, std::size_t at) {
            const std::size_t start = Dyn::DecimalRun(text, at);
            if (start == 0) return 0;
            std::size_t end = at + start;
            if (end < text.size() && text[end] == ',') {
                const std::size_t count = Dyn::DecimalRun(text, end + 1);
                if (count > 0) end += 1 + count;
            }
            return end - at;
        }

        // ^@@ -\d+(?:,\d+)? \+\d+(?:,\d+)? @@(.*)$ -> group(1)
        std::optional<std::string_view> HunkTail(std::string_view line) {
            if (!line.starts_with("@@ -")) return std::nullopt;
            std::size_t at = 4;
            const std::size_t old = LineRange(line, at);
            if (old == 0) return std::nullopt;
            at += old;
            if (!line.substr(at).starts_with(" +")) return std::nullopt;
            at += 2;
            const std::size_t now = LineRange(line, at);
            if (now == 0) return std::nullopt;
            at += now;
            if (!line.substr(at).starts_with(" @@")) return std::nullopt;
            return line.substr(at + 3);
        }

        // Every line start that `head` follows: where the text is cut.
        // Position 0 is one when the text starts with it, which makes the
        // first piece empty.
        std::vector<std::string> SplitBeforeLines(std::string_view text, std::string_view head) {
            std::vector<std::size_t> cuts;
            for (std::size_t at = 0; at <= text.size();) {
                if (text.substr(at).starts_with(head)) cuts.push_back(at);
                const std::size_t newline = text.find('\n', at);
                if (newline == std::string_view::npos) break;
                at = newline + 1;
            }
            std::vector<std::string> pieces;
            std::size_t from = 0;
            for (const std::size_t cut : cuts) {
                pieces.emplace_back(text.substr(from, cut - from));
                from = cut;
            }
            pieces.emplace_back(text.substr(from));
            return pieces;
        }

        // re.sub(r'^Subject: (\[[^\]]*\]\s*)*', 'Subject: ', line): the
        // `[PATCH n/m]` tags after `Subject: ` dropped, and the space after
        // each.
        std::string StripSubjectTags(std::string_view line) {
            if (!line.starts_with("Subject: ")) return std::string(line);
            std::size_t at = 9;
            while (at < line.size() && line[at] == '[') {
                const std::size_t close = line.find(']', at + 1);
                if (close == std::string_view::npos) break;
                at = close + 1;
                at += Dyn::SpaceRun(line, at);
            }
            return std::format("Subject: {}", line.substr(at));
        }

        // ^base-commit: [0-9a-f]{40}$
        bool IsBaseCommit(std::string_view line) {
            constexpr std::string_view Head = "base-commit: ";
            return line.size() == Head.size() + 40 && line.starts_with(Head) && IsHex(line.substr(Head.size()));
        }

        std::int64_t IntItem(const Json& range, std::size_t index) {
            const Json& value = range.at(index);
            if (value.is_boolean()) return value.get<bool>() ? 1 : 0;
            return value.get<std::int64_t>();
        }

        Json Mechanical(std::string_view name, std::string_view lensFile, const Json& unit, std::string_view text, std::string_view basis) {
            const std::string id = Dyn::At(unit, "id").get<std::string>();
            return {
                {"label", std::format("{}:na:{}", name, id)},
                {"lens", name},
                {"lensFile", lensFile},
                {"kind", "auto-na"},
                {"unit", id},
                {"expectedIds", {id}},
                {"unitSha", Sha(text)},
                {"basis", basis},
            };
        }

        bool Contains(std::span<const std::string> list, std::string_view item) {
            return std::ranges::contains(list, item);
        }

        // any(l[:1] in ('+', '-') and l[1:].strip() for l in code_norm(text).split('\n')):
        // does the commit add or remove a line with something on it in this
        // part of a documentation hunk?
        bool WritesIn(std::string_view text) {
            for (const std::string& line : Dyn::Split(CodeNorm(text), "\n")) {
                if ((line.starts_with('+') || line.starts_with('-')) && !Dyn::Strip(line.substr(1)).empty()) return true;
            }
            return false;
        }
    }

    std::vector<ModelTier>& Models() {
        static std::vector<ModelTier> models = {{"opus", "claude-opus-5-5"}, {"fable", "claude-opus-5-5"}};
        return models;
    }

    const std::string& ModelFor(std::string_view tier) {
        for (const ModelTier& model : Models()) {
            if (model.tier == tier) return model.id;
        }
        throw Dyn::Error("KeyError", Dyn::Repr(tier));
    }

    bool IsKernelMode(std::string_view mode) {
        return mode == "reply" || mode == "series";
    }

    std::int32_t ReadsFor(std::string_view mode) {
        return mode == "reply" ? ReplyReads : Reads;
    }

    bool IsLens(std::string_view file) {
        return std::ranges::any_of(Lenses, [&](const Lens& lens) { return lens.file == file; });
    }

    const Lens& LensOf(std::string_view file) {
        for (const Lens& lens : Lenses) {
            if (lens.file == file) return lens;
        }
        throw Dyn::Error("KeyError", Dyn::Repr(file));
    }

    const std::vector<Gate>& Gates(std::string_view mode) {
        static const std::vector<Gate> commits = {
            {"Gate 1 — Approach", {"repo-better-solution.md"}},
            {"Gate 2 — Functional", {FunctionalLens}},
            {"Gate 3 — Proof", {"repo-bug-prover.md", "repo-security.md"}},
            {"Gate 4 — Commit truth", {FactsLens}},
        };
        static const std::vector<Gate> reply = {
            {"Gate 3 — Artifact truth", {"facts.md", "etiquette.md", "consistency.md", "conciseness.md"}},
        };
        static const std::vector<Gate> series = {
            {"Gate 1 — Structure", {"better-solution.md"}},
            {"Gate 2 — Code", {"code-quality.md", "minimalism.md", "bug-prover.md"}},
            {"Gate 3 — Artifact truth", {"facts.md", "consistency.md", "process-docs.md", "etiquette.md", "conciseness.md"}},
        };
        if (mode == "reply") return reply;
        if (mode == "series") return series;
        if (mode == "commits") return commits;
        throw Dyn::Error("KeyError", Dyn::Repr(mode));
    }

    const Environment* FindEnvironment(std::string_view name) {
        for (const Environment& environment : Environments) {
            if (environment.name == name) return &environment;
        }
        return nullptr;
    }

    std::vector<std::string> EnvDeps(std::string_view lensFile, std::string_view environment) {
        const std::string_view fallback = LensOf(lensFile).env;
        const std::string_view used = environment.empty() ? fallback : environment;
        if (used == fallback) return {};
        return {std::format("env={}", used)};
    }

    Budget BudgetFor(std::string_view kind, std::string_view unitKind, std::string_view lensFile) {
        if (kind == "whole") return lensFile == FunctionalLens ? Budget{220, 120} : Budget{180, 105};
        if (kind == "slot") return {50, 35};
        if (unitKind == "code") return lensFile == FunctionalLens ? Budget{90, 60} : Budget{60, 40};
        if (unitKind == "doc") return {60, 40};
        // The facts lens of the kernel modes gets the most (2026-09-28: a
        // facts pass on the densest unit used 58 of 60 calls and left one
        // claim unverified).
        if (unitKind == "text") return lensFile == "facts.md" ? Budget{80, 50} : lensFile == FactsLens ? Budget{60, 40} : Budget{50, 30};
        throw Dyn::Error("KeyError", Dyn::Repr(std::format("block:{}", unitKind)));
    }

    std::string_view DefaultEffort() {
        return Effort;
    }

    std::string_view DefaultEffort(std::string_view mode) {
        return IsKernelMode(mode) ? KernelEffort : Effort;
    }

    bool IsBareHeader(const Json& unit, std::string_view text) {
        constexpr std::array<std::string_view, 4> Bare = {"camss-milos", "ov13b10-of", "milos-dts-camss", "across the three series"};
        const std::string& id = Dyn::At(unit, "id").get_ref<const std::string&>();
        return id.ends_with(":header") && std::ranges::contains(Bare, std::string_view(Dyn::Lower(Dyn::Strip(text))));
    }

    std::string_view UnitKindOf(std::string_view unitId) {
        if (unitId.starts_with("whole:")) return "slot";
        const std::optional<std::size_t> prefix = PkPrefix(unitId);
        if (!prefix) return "text";
        // `$` also matches before a final newline.
        std::string_view name = unitId.substr(*prefix);
        if (name.ends_with('\n')) name.remove_suffix(1);
        if (name == "subject" || name == "msg" || name == "trailers" || name == "diffstat") return "text";
        return "code";
    }

    std::string_view UnitKind(const Json& unit) {
        return UnitKindOf(Dyn::At(unit, "id").get_ref<const std::string&>());
    }

    bool IsDocPath(std::string_view path) {
        auto endsWithMd = [](std::string_view text) {
            const std::u32string decoded = Dyn::Decode(text);
            if (decoded.size() < 3) return false;
            const std::size_t n = decoded.size();
            return decoded[n - 3] == '.' && Dyn::IgnoreCaseLetter(decoded[n - 2]) == 'm' && Dyn::IgnoreCaseLetter(decoded[n - 1]) == 'd';
        };
        return endsWithMd(path) || (path.ends_with('\n') && endsWithMd(path.substr(0, path.size() - 1)));
    }

    bool IsDocUnit(std::string_view unitId) {
        const std::optional<std::string_view> path = FileOfUnit(unitId);
        return path && IsDocPath(*path);
    }

    // For the repo lenses the units of a documentation file are "doc" - the
    // commit-truth lens reads them, the code lenses do not; for the kernel
    // lenses every unit of a diff stays code.
    std::string_view KindFor(std::string_view lensFile, const Json& unit) {
        const std::string_view kind = UnitKind(unit);
        if (IsLens(lensFile) && LensOf(lensFile).kernel) return kind;
        return kind == "code" && IsDocUnit(Dyn::At(unit, "id").get_ref<const std::string&>()) ? "doc" : kind;
    }

    std::optional<std::string> UnitPath(std::string_view unitId) {
        const std::optional<std::string_view> path = FileOfUnit(unitId);
        if (!path) return std::nullopt;
        return std::string(*path);
    }

    std::vector<std::string> NotReviewed(const Json& units, std::span<const std::string> lines, std::span<const std::string> lensFiles,
                                         std::span<const std::string> exclude) {
        std::set<std::string> covered;
        for (const std::string& lensFile : lensFiles) {
            const LensPlan plan = PlanLens(lensFile, units, lines, {}, exclude);
            if (Dyn::Truthy(plan.whole)) {
                for (const Json& id : Dyn::At(plan.whole, "expectedIds")) covered.insert(id.get<std::string>());
            }
            for (const Json& block : plan.blocks) {
                if (Dyn::At(block, "kind") != "auto-na") covered.insert(Dyn::At(block, "unit").get<std::string>());
            }
        }
        std::vector<std::string> out;
        for (const Json& unit : units) {
            const std::string& id = Dyn::At(unit, "id").get_ref<const std::string&>();
            if (!covered.contains(id)) out.push_back(id);
        }
        return out;
    }

    std::optional<std::string> ExcludedBy(std::string_view path, std::span<const std::string> globs) {
        for (const std::string& glob : globs) {
            if (Dyn::FnMatch(path, glob) || (glob.starts_with("**/") && Dyn::FnMatch(path, std::string_view(glob).substr(3)))) return glob;
        }
        return std::nullopt;
    }

    std::string UnitText(std::span<const std::string> lines, const Json& unit) {
        const Json& range = Dyn::At(unit, "lines");
        const std::int64_t a = IntItem(range, 0);
        const std::int64_t b = IntItem(range, 1);
        if (a == 0) return "";
        const auto [from, to] = Dyn::SliceBounds(lines.size(), a - 1, b);
        return Dyn::Join(lines.subspan(from, to - from), "\n");
    }

    std::string Sha(std::string_view text) {
        return Sha256Hex(text);
    }

    std::string LensName(std::string_view lensFile, std::string_view persona) {
        if (!persona.empty()) return std::format("persona:{}", persona);
        return Dyn::Replace(lensFile, ".md", "");
    }

    std::vector<std::string> ModeLenses(std::string_view mode) {
        std::vector<std::string> out;
        for (const Gate& gate : Gates(mode)) {
            for (const std::string_view lens : gate.lenses) out.emplace_back(lens);
        }
        if (IsKernelMode(mode)) out.emplace_back(PersonaLens);
        return out;
    }

    std::vector<Gate> GatesFor(std::span<const std::string> only, std::span<const std::string> without, std::span<const std::string> off) {
        return GatesFor("commits", only, without, off);
    }

    std::vector<Gate> GatesFor(std::string_view mode, std::span<const std::string> only, std::span<const std::string> without, std::span<const std::string> off) {
        std::vector<Gate> out;
        for (const Gate& gate : Gates(mode)) {
            Gate kept{gate.title, {}};
            for (const std::string_view lens : gate.lenses) {
                if (!only.empty() && !Contains(only, lens)) continue;
                if (Contains(without, lens) || Contains(off, lens)) continue;
                kept.lenses.push_back(lens);
            }
            if (!kept.lenses.empty()) out.push_back(std::move(kept));
        }
        return out;
    }

    LensPlan PlanLens(std::string_view lensFile, const Json& units, std::span<const std::string> lines, std::span<const std::string> unitsFilter,
                      std::span<const std::string> exclude, std::string_view persona, std::span<const std::string> excludeUnits) {
        const Lens& lens = LensOf(lensFile);
        const std::string name = LensName(lensFile, persona);
        // A persona's jobs carry its name, after the lens file.
        auto stamp = [&](Json job) {
            if (persona.empty()) return job;
            Json out = Json::object();
            for (auto it = job.begin(); it != job.end(); ++it) {
                out[it.key()] = it.value();
                if (it.key() == "lensFile") out["persona"] = persona;
            }
            return out;
        };
        LensPlan plan;
        if (!lens.whole.empty()) {
            const Budget budget = BudgetFor("whole", "", lensFile);
            Json slots = Json::array();
            for (const Json& unit : units) {
                const std::string& id = Dyn::At(unit, "id").get_ref<const std::string&>();
                // A kernel lens's whole pass covers every whole:* slot of the
                // artifact; a repo lens's the slots the table names.
                if (UnitKind(unit) == "slot" && (lens.kernel || std::ranges::contains(lens.slots, std::string_view(id)))) slots.push_back(id);
            }
            plan.whole = stamp({
                {"label", std::format("{}:whole", name)},
                {"lens", name},
                {"lensFile", lensFile},
                {"kind", "whole"},
                {"unit", nullptr},
                {"expectedIds", slots},
                {"model", ModelFor(lens.model)},
                {"maxTurns", budget.maxTurns},
                {"timeoutMin", budget.timeoutMin},
            });
        }
        for (const Json& unit : units) {
            const std::string_view kind = KindFor(lensFile, unit);
            if (!std::ranges::contains(lens.block, kind)) continue;
            const std::string& id = Dyn::At(unit, "id").get_ref<const std::string&>();
            if (Contains(excludeUnits, id)) continue;
            if (!unitsFilter.empty() && !Contains(unitsFilter, id)) continue;
            const std::string text = UnitText(lines, unit);
            const std::optional<std::string> path = UnitPath(id);
            if (kind == "slot") {
                // A lens with no whole pass asks each of its own slots in a
                // pass of its own; another lens's whole slot is not its. A
                // kernel lens asks every whole:* slot.
                if (!lens.kernel && !std::ranges::contains(lens.slots, std::string_view(id))) continue;
                const Budget budget = BudgetFor("slot", "slot", lensFile);
                plan.blocks.push_back(stamp({
                    {"label", std::format("{}:slot:{}", name, id)},
                    {"lens", name},
                    {"lensFile", lensFile},
                    {"kind", "slot"},
                    {"unit", id},
                    {"unitKind", "slot"},
                    {"expectedIds", {id}},
                    {"unitSha", Sha(text)},
                    {"model", ModelFor(lens.model)},
                    {"maxTurns", budget.maxTurns},
                    {"timeoutMin", budget.timeoutMin},
                }));
                continue;
            }
            if (kind == "text" && IsBareHeader(unit, text)) {
                plan.blocks.push_back(stamp({
                    {"label", std::format("{}:na:{}", name, id)},
                    {"lens", name},
                    {"lensFile", lensFile},
                    {"kind", "auto-na"},
                    {"unit", id},
                    {"expectedIds", {id}},
                    {"unitSha", Sha(text)},
                }));
                continue;
            }
            if (kind == "doc" && id.ends_with("#hdr")) {
                // The diff header of a documentation file names the file, its
                // blobs and its mode: no sentence, no claim.
                plan.blocks.push_back(Mechanical(name, lensFile, unit, text, "mechanical: diff header of a documentation file"));
                continue;
            }
            if (kind == "doc" && !WritesIn(text)) {
                // A part of a hunk that holds only context (the lines above a
                // section the commit adds): nothing was written here.
                plan.blocks.push_back(Mechanical(name, lensFile, unit, text, "mechanical: context only - the commit adds and removes no line in this part"));
                continue;
            }
            if (!lens.perCommitSlots && (id.ends_with(":outside") || id.ends_with(":absent"))) {
                // The functional lens judges adjacent flows and what is missing
                // in its whole pass, not per commit.
                continue;
            }
            if (lensFile == FunctionalLens && path && id.ends_with("#hdr")) {
                plan.blocks.push_back(Mechanical(name, lensFile, unit, text,
                    "mechanical: a diff header (mode, rename, new or deleted file) carries no behaviour of its own; the hunks of the file do"));
                continue;
            }
            if (lensFile == FunctionalLens && path) {
                if (const std::optional<std::string> glob = ExcludedBy(*path, exclude)) {
                    plan.blocks.push_back(Mechanical(name, lensFile, unit, text,
                        std::format("mechanical: no runtime behaviour - the file matches functional.exclude ({})", *glob)));
                    continue;
                }
            }
            const Budget budget = BudgetFor("block", kind, lensFile);
            plan.blocks.push_back(stamp({
                {"label", std::format("{}:block:{}", name, id)},
                {"lens", name},
                {"lensFile", lensFile},
                {"kind", "block"},
                {"unit", id},
                {"unitKind", kind},
                {"expectedIds", {id}},
                {"unitSha", Sha(text)},
                {"model", ModelFor(lens.model)},
                {"maxTurns", budget.maxTurns},
                {"timeoutMin", budget.timeoutMin},
            }));
        }
        return plan;
    }

    std::optional<std::string> ReuseKey(const Json& job, std::string_view lensFile, std::string_view unitText, std::vector<std::string> deps,
                                        std::vector<std::string> inForceIds, std::string_view charterSha, std::int32_t promptVersion,
                                        std::string_view ident) {
        if (!LensOf(lensFile).reuse || Dyn::At(job, "kind") != "block") return std::nullopt;
        std::ranges::sort(deps);
        std::ranges::sort(inForceIds);
        const Json& model = Dyn::Get(job, "model");
        std::vector<std::string> parts = {
            std::string(lensFile),
            ident.empty() ? Dyn::At(job, "unit").get<std::string>() : std::string(ident),
            Sha(unitText),
            Sha(Dyn::Join(deps, "\n")),
            Dyn::Join(inForceIds, ","),
            std::string(charterSha),
            std::to_string(promptVersion),
            Dyn::Has(job, "model") ? model.get<std::string>() : std::string(),
            std::string(ReuseKeyEffortSlot),
        };
        if (Dyn::Truthy(Dyn::Get(job, "persona"))) parts.push_back(std::format("persona={}", Dyn::Str(job.at("persona"))));
        return Sha(Dyn::Join(parts, "|")).substr(0, 16);
    }

    std::string CodeNorm(std::string_view text) {
        std::vector<std::string> lines = Dyn::Split(text, "\n");
        while (!lines.empty() && lines.back().empty()) lines.pop_back();
        if (lines.size() >= 2 && lines[lines.size() - 2] == "-- " && StartsWithVersion(lines.back())) {
            lines.resize(lines.size() - 2);
            while (!lines.empty() && (lines.back().empty() || IsTailLine(lines.back()))) lines.pop_back();
        }
        for (std::string& line : lines) {
            if (const std::optional<std::string_view> mode = IndexMode(line)) {
                line = std::format("index{}", *mode);
            } else if (const std::optional<std::string_view> tail = HunkTail(line)) {
                line = std::format("@@{}", *tail);
            }
        }
        return Dyn::Join(lines, "\n");
    }

    PatchParts PartsOf(std::string_view patchText, bool docFiles) {
        const std::vector<std::string> lines = Dyn::Split(patchText, "\n");
        std::optional<std::size_t> subject;
        for (std::size_t i = 0; i < lines.size(); ++i) {
            if (lines[i].starts_with("Subject:")) {
                subject = i;
                break;
            }
        }
        std::size_t body0 = 1;
        if (subject) {
            for (std::size_t i = *subject + 1; i < lines.size(); ++i) {
                if (Dyn::Strip(lines[i]).empty()) {
                    body0 = i + 1;
                    break;
                }
            }
        }
        std::size_t diff0 = lines.size();
        for (std::size_t i = body0; i < lines.size(); ++i) {
            if (lines[i].starts_with("---")) {
                diff0 = i;
                break;
            }
        }
        std::size_t first = lines.size();
        for (std::size_t i = diff0 + 1; i < lines.size(); ++i) {
            if (lines[i].starts_with("diff --git")) {
                first = i;
                break;
            }
        }
        PatchParts parts;
        for (const std::string& line : lines) {
            if (IsBaseCommit(line)) {
                parts.base = Dyn::Split(line)[1];
                break;
            }
        }
        const std::span<const std::string> code(lines.begin() + static_cast<std::ptrdiff_t>(std::min(first, lines.size())), lines.end());
        for (const std::string& section : SplitBeforeLines(CodeNorm(Dyn::Join(code, "\n")), "diff --git ")) {
            const std::string firstLine = Dyn::Split(section, "\n", 1)[0];
            const std::string path = Dyn::Strip(Dyn::Split(firstLine, " b/").back());
            if (docFiles && section.starts_with("diff --git ") && IsDocPath(path)) {
                // re.split(r'(?m)^@@', section, maxsplit=1)[0].rstrip('\n')
                std::size_t header = section.size();
                for (std::size_t at = 0; at < section.size();) {
                    if (std::string_view(section).substr(at).starts_with("@@")) {
                        header = at;
                        break;
                    }
                    const std::size_t newline = section.find('\n', at);
                    if (newline == std::string::npos) break;
                    at = newline + 1;
                }
                parts.docs.push_back(Dyn::RStrip(std::string_view(section).substr(0, header), "\n"));
            } else {
                parts.code += section;
            }
        }
        std::ranges::sort(parts.docs);
        const auto [messageFrom, messageTo] = Dyn::SliceBounds(lines.size(), static_cast<std::int64_t>(subject ? *subject : body0), static_cast<std::int64_t>(diff0));
        std::vector<std::string> message;
        for (std::size_t i = messageFrom; i < messageTo; ++i) message.push_back(StripSubjectTags(lines[i]));
        parts.message = Dyn::Join(message, "\n");
        const auto [bodyFrom, bodyTo] = Dyn::SliceBounds(lines.size(), static_cast<std::int64_t>(body0), static_cast<std::int64_t>(diff0));
        for (std::size_t i = bodyFrom; i < bodyTo; ++i) {
            if (!Dyn::Strip(lines[i]).empty()) {
                parts.hasBody = true;
                break;
            }
        }
        return parts;
    }

    CommitCode CommitCodeOf(const std::map<std::int64_t, std::string>& patches, bool kernel) {
        CommitCode cc;
        cc.kernel = kernel;
        std::set<std::string> bases;
        std::vector<std::string> codes;
        for (const auto& [k, text] : patches) {
            PatchParts parts = PartsOf(text, !kernel);
            cc.body[k] = parts.hasBody;
            cc.code[k] = Sha(parts.code);
            cc.docs[k] = std::move(parts.docs);
            cc.message[k] = Sha(parts.message);
            if (!parts.base.empty()) bases.insert(parts.base);
            codes.push_back(cc.code[k]);
            cc.upto[k] = Sha(Dyn::Join(codes, "\n"));
        }
        cc.range = Sha(Dyn::Join(codes, "\n"));
        cc.base = Dyn::Join(std::vector<std::string>(bases.begin(), bases.end()), ",");
        return cc;
    }

    std::pair<std::string, std::vector<std::string>> CodeKeyParts(std::string_view unitId, const CommitCode& cc) {
        const std::size_t colon = unitId.find(':');
        if (colon == std::string_view::npos) throw Dyn::Error("ValueError", "not enough values to unpack (expected 2, got 1)");
        const std::string_view pk = unitId.substr(0, colon);
        const std::string_view rest = unitId.substr(colon + 1);
        const std::string_view number = pk.empty() ? pk : pk.substr(1);
        const std::optional<std::int64_t> k = Dyn::ParseInt(number);
        if (!k) throw Dyn::Error("ValueError", Dyn::IntError(number));
        std::vector<std::string> deps = {std::format("base={}", cc.base)};
        if (rest == "outside" || rest == "absent") {
            const auto code = cc.code.find(*k);
            if (code == cc.code.end()) throw Dyn::Error("KeyError", std::to_string(*k));
            deps.push_back(std::format("commit={}:{}", *k, code->second));
            deps.push_back(std::format("range={}", cc.range));
            deps.push_back(std::format("docs={}", Dyn::Join(cc.docs.at(*k), "|")));
            // A kernel reviewer looks for a trailer, a Cc, a test statement:
            // the patch's message is what `absent` depends on there; in an
            // own repository it looks for a body at all.
            if (rest == "absent") deps.push_back(cc.kernel ? std::format("msg={}", cc.message.at(*k)) : std::format("body={}", cc.body.at(*k) ? "yes" : "no"));
            return {std::format("code:{}", rest), deps};
        }
        const std::size_t hash = rest.rfind('#');
        if (hash == std::string_view::npos) throw Dyn::Error("ValueError", "not enough values to unpack (expected 2, got 1)");
        const std::string_view tag = rest.substr(hash + 1);
        return {std::format("code:{}#{}", rest.substr(0, hash), tag == "hdr" ? "hdr" : "hunk"), deps};
    }

    std::optional<std::string> CodeReuseKey(const Json& job, std::string_view lensFile, std::string_view unitText, const CommitCode& cc,
                                            std::span<const std::string> inForceIds, std::string_view charterSha, std::int32_t promptVersion,
                                            std::string_view environment) {
        auto [ident, deps] = CodeKeyParts(Dyn::At(job, "unit").get_ref<const std::string&>(), cc);
        std::ranges::move(EnvDeps(lensFile, environment), std::back_inserter(deps));
        return ReuseKey(job, lensFile, CodeNorm(unitText), deps, {inForceIds.begin(), inForceIds.end()}, charterSha, promptVersion, ident);
    }

    std::optional<std::string> FunctionalReuseKey(const Json& job, std::string_view lensFile, std::string_view unitText, const CommitCode& cc,
                                                  std::span<const std::string> inForceIds, std::string_view charterSha, std::int32_t promptVersion,
                                                  std::string_view environment) {
        auto [ident, deps] = CodeKeyParts(Dyn::At(job, "unit").get_ref<const std::string&>(), cc);
        deps.push_back(std::format("range={}", cc.range));
        std::ranges::move(EnvDeps(lensFile, environment), std::back_inserter(deps));
        return ReuseKey(job, lensFile, CodeNorm(unitText), deps, {inForceIds.begin(), inForceIds.end()}, charterSha, promptVersion,
                        std::format("functional:{}", ident));
    }

    std::pair<std::string, std::vector<std::string>> DocKeyParts(std::string_view unitId, const CommitCode& cc) {
        const std::size_t colon = unitId.find(':');
        if (colon == std::string_view::npos) throw Dyn::Error("ValueError", "not enough values to unpack (expected 2, got 1)");
        const std::string_view rest = unitId.substr(colon + 1);
        const std::size_t hash = rest.rfind('#');
        return {std::format("doc:{}", hash == std::string_view::npos ? rest : rest.substr(0, hash)), {std::format("base={}", cc.base), std::format("range={}", cc.range)}};
    }

    std::vector<std::string> MessageDeps(std::string_view unitId, const CommitCode& cc) {
        // ^p(\d+):(subject|msg)$; `$` also matches before a final newline.
        const std::optional<std::size_t> prefix = PkPrefix(unitId);
        if (!prefix) return {};
        std::string_view name = unitId.substr(*prefix);
        if (name.ends_with('\n')) name.remove_suffix(1);
        if (name != "subject" && name != "msg") return {};
        const std::string_view number = unitId.substr(1, *prefix - 2);
        const std::optional<std::int64_t> k = Dyn::ParseInt(number);
        if (!k) throw Dyn::Error("ValueError", Dyn::IntError(number));
        const auto upto = cc.upto.find(*k);
        if (upto == cc.upto.end()) throw Dyn::Error("KeyError", std::to_string(*k));
        return {std::format("base={}", cc.base), std::format("upto={}", upto->second)};
    }

    std::optional<std::string> DocReuseKey(const Json& job, std::string_view lensFile, std::string_view unitText, const CommitCode& cc,
                                           std::span<const std::string> inForceIds, std::string_view charterSha, std::int32_t promptVersion,
                                           std::string_view environment) {
        auto [ident, deps] = DocKeyParts(Dyn::At(job, "unit").get_ref<const std::string&>(), cc);
        std::ranges::move(EnvDeps(lensFile, environment), std::back_inserter(deps));
        return ReuseKey(job, lensFile, CodeNorm(unitText), deps, {inForceIds.begin(), inForceIds.end()}, charterSha, promptVersion, ident);
    }

    std::optional<std::string> TextReuseKey(const Json& job, std::string_view lensFile, std::string_view unitText, const CommitCode& cc,
                                            std::span<const std::string> inForceIds, std::string_view charterSha, std::int32_t promptVersion,
                                            std::string_view environment) {
        std::vector<std::string> deps = MessageDeps(Dyn::At(job, "unit").get_ref<const std::string&>(), cc);
        std::ranges::move(EnvDeps(lensFile, environment), std::back_inserter(deps));
        return ReuseKey(job, lensFile, unitText, deps, {inForceIds.begin(), inForceIds.end()}, charterSha, promptVersion);
    }

    std::optional<std::string> BlockReuseKey(const Json& job, std::string_view lensFile, std::string_view unitText, const CommitCode& cc,
                                             std::span<const std::string> inForceIds, std::string_view charterSha, std::int32_t promptVersion,
                                             std::string_view environment) {
        // A slot pass and a whole pass have no block key (ReuseKey's own
        // rule, before any id is parsed: a `whole:*` id has no commit number).
        if (Dyn::At(job, "kind") != "block") return std::nullopt;
        const Json& unitKind = Dyn::Get(job, "unitKind");
        if (unitKind == "doc") return DocReuseKey(job, lensFile, unitText, cc, inForceIds, charterSha, promptVersion, environment);
        if (unitKind == "text") return TextReuseKey(job, lensFile, unitText, cc, inForceIds, charterSha, promptVersion, environment);
        if (LensOf(lensFile).key == "functional") {
            return FunctionalReuseKey(job, lensFile, unitText, cc, inForceIds, charterSha, promptVersion, environment);
        }
        return CodeReuseKey(job, lensFile, unitText, cc, inForceIds, charterSha, promptVersion, environment);
    }

    std::optional<std::string> WholeCodeKey(const Json& job, std::string_view lensFile, const CommitCode& cc, std::span<const std::string> inForceIds,
                                            std::string_view charterSha, std::int32_t promptVersion, std::string_view environment) {
        if (!LensOf(lensFile).wholeReuse || Dyn::At(job, "kind") != "whole") return std::nullopt;
        std::string body;
        for (const auto& [k, has] : cc.body) {
            if (!body.empty()) body.push_back(',');
            body.push_back(has ? 'y' : 'n');
        }
        std::vector<std::string> docs;
        for (const auto& [k, files] : cc.docs) docs.push_back(Dyn::Join(files, "|"));
        std::vector<std::string> deps = {
            std::format("base={}", cc.base),
            std::format("range={}", cc.range),
            std::format("body={}", body),
            std::format("docs={}", Dyn::Join(docs, ";")),
        };
        std::ranges::move(EnvDeps(lensFile, environment), std::back_inserter(deps));
        std::vector<std::string> ids(inForceIds.begin(), inForceIds.end());
        std::ranges::sort(ids);
        const std::vector<std::string> parts = {
            std::string(lensFile),
            "code:whole",
            Sha(Dyn::Join(deps, "\n")),
            Dyn::Join(ids, ","),
            std::string(charterSha),
            std::to_string(promptVersion),
            Dyn::Has(job, "model") ? Dyn::Get(job, "model").get<std::string>() : std::string(),
            std::string(ReuseKeyEffortSlot),
        };
        return Sha(Dyn::Join(parts, "|")).substr(0, 16);
    }

    namespace {
        // \b before `at` and after `end` in the decoded text.
        bool Bounded(const std::u32string& text, std::size_t at, std::size_t end) {
            const bool before = at == 0 || !Dyn::IsWord(text[at - 1]);
            const bool after = end >= text.size() || !Dyn::IsWord(text[end]);
            return before && after;
        }

        // A phrase at `at`, letters compared without case.
        bool PhraseAt(const std::u32string& text, std::size_t at, std::string_view phrase) {
            if (at + phrase.size() > text.size()) return false;
            for (std::size_t i = 0; i < phrase.size(); ++i) {
                const char32_t c = text[at + i];
                const char p = phrase[i];
                if (p >= 'a' && p <= 'z') {
                    if (Dyn::IgnoreCaseLetter(c) != p) return false;
                } else if (c != static_cast<char32_t>(p)) {
                    return false;
                }
            }
            return true;
        }

        // re.search(r'\d{4}-\d{2}-\d{2}|\bv\d+\b|\bas of\b|...', text, re.I)
        bool Dated(std::string_view unitText) {
            constexpr std::array<std::string_view, 9> Words = {"as of", "still", "unmerged", "in review", "no reply", "latest", "merged", "posted", "applied"};
            const std::u32string text = Dyn::Decode(unitText);
            auto digits = [&](std::size_t at, std::size_t n) {
                for (std::size_t i = 0; i < n; ++i) {
                    if (at + i >= text.size() || !Dyn::IsDecimal(text[at + i])) return false;
                }
                return true;
            };
            for (std::size_t at = 0; at < text.size(); ++at) {
                if (digits(at, 4) && at + 4 < text.size() && text[at + 4] == '-' && digits(at + 5, 2) && at + 7 < text.size() && text[at + 7] == '-' && digits(at + 8, 2)) return true;
                if (Dyn::IgnoreCaseLetter(text[at]) == 'v' && at + 1 < text.size() && Dyn::IsDecimal(text[at + 1])) {
                    std::size_t end = at + 1;
                    while (end < text.size() && Dyn::IsDecimal(text[end])) ++end;
                    if (Bounded(text, at, end)) return true;
                }
                for (const std::string_view word : Words) {
                    if (PhraseAt(text, at, word) && Bounded(text, at, at + word.size())) return true;
                }
            }
            return false;
        }

        // re.fullmatch(r'R\d+', id)
        bool IsReversalId(std::string_view id) {
            return id.size() > 1 && id[0] == 'R' && Dyn::DecimalRun(id, 1) == id.size() - 1;
        }

        // re.search(r'\b' + re.escape(id) + r'\b', text)
        bool NamesUnit(std::string_view unitText, std::string_view id) {
            const std::u32string text = Dyn::Decode(unitText);
            const std::u32string needle = Dyn::Decode(id);
            for (std::size_t at = 0; at + needle.size() <= text.size(); ++at) {
                if (std::u32string_view(text).substr(at, needle.size()) == needle && Bounded(text, at, at + needle.size())) return true;
            }
            return false;
        }
    }

    std::vector<std::string> TextDeps(std::string_view unitText, const Json& units, std::span<const std::string> lines, std::span<const std::pair<std::string, std::string>> refs,
                                      std::string_view anchorText) {
        std::vector<std::string> deps;
        // sorted(set(int(x) for x in re.findall(r'\[(\d+)\]', text)))
        std::set<std::int64_t> cited;
        for (std::size_t at = 0; at < unitText.size(); ++at) {
            if (unitText[at] != '[') continue;
            const std::size_t digits = Dyn::DecimalRun(unitText, at + 1);
            if (digits == 0 || at + 1 + digits >= unitText.size() || unitText[at + 1 + digits] != ']') continue;
            if (const std::optional<std::int64_t> n = Dyn::ParseInt(unitText.substr(at + 1, digits))) cited.insert(*n);
            at += digits + 1;
        }
        for (const std::int64_t n : cited) {
            std::string url = "?";
            for (const auto& [key, value] : refs) {
                if (key == std::to_string(n)) url = value;
            }
            deps.push_back(std::format("ref[{}]={}", n, url));
        }
        if (Dated(unitText)) deps.push_back(std::format("anchor={}", Sha(anchorText)));
        for (const Json& unit : units) {
            const std::string& id = Dyn::At(unit, "id").get_ref<const std::string&>();
            if (IsReversalId(id) && NamesUnit(unitText, id)) deps.push_back(std::format("unit[{}]={}", id, Sha(UnitText(lines, unit))));
        }
        return deps;
    }

    std::int64_t ReadsOf(const Json& entry) {
        if (!Dyn::Truthy(entry)) return 0;
        const Json& reads = Dyn::Get(entry, "reads");
        if (!Dyn::Truthy(reads)) return 1;
        if (reads.is_string()) return static_cast<std::int64_t>(Dyn::Length(reads.get_ref<const std::string&>()));
        return static_cast<std::int64_t>(reads.size());
    }

    bool ReadIn(const Json& entry, std::string_view hash8, std::int64_t round) {
        const Json& reads = Dyn::Or(Dyn::Get(entry, "reads"), Dyn::EmptyList());
        return std::ranges::any_of(reads, [&](const Json& read) {
            return Dyn::Equal(Dyn::Get(read, "hash"), Json(hash8)) && Dyn::Equal(Dyn::Get(read, "round"), Json(round));
        });
    }

    Json Rebind(const Json& entry, std::string_view unitId) {
        Json out = entry;
        out["unit"] = unitId;
        Json coverage = Dyn::At(out, "coverage");
        if (!coverage.is_object()) throw Dyn::Error("TypeError", std::format("'{}' object is not iterable", Dyn::TypeName(coverage)));
        coverage["item"] = unitId;
        out["coverage"] = std::move(coverage);
        for (const std::string_view field : {std::string_view("findings"), std::string_view("notes")}) {
            if (!Dyn::Has(out, field)) continue;
            for (Json& item : out[std::string(field)]) {
                if (Dyn::Get(item, "items").is_array()) item["items"] = Json::array({unitId});
            }
        }
        return out;
    }

    Json Estimate(std::span<const Json> jobs, std::int64_t prefixBytes, const std::map<std::string, std::int64_t>& lensLayerBytes,
                  std::int64_t tailBytes, double tpb, std::int64_t sysTokens, std::int64_t outPerTurn) {
        const double prefix = static_cast<double>(prefixBytes) / tpb + static_cast<double>(sysTokens);
        double cacheRead = 0.0;
        double cacheWrite = 0.0;
        double output = 0.0;
        std::int64_t processes = 0;
        std::set<std::pair<std::string, std::string>> seen;
        for (const Json& job : jobs) {
            const std::string kind = Dyn::At(job, "kind").get<std::string>();
            if (kind == "auto-na") continue;
            const std::string lens = Dyn::At(job, "lens").get<std::string>();
            const auto layer = lensLayerBytes.find(lens);
            const double lensTokens = static_cast<double>(layer == lensLayerBytes.end() ? 3000 : layer->second) / tpb;
            const double tail = static_cast<double>(tailBytes) / tpb;
            const Json& unitKind = Dyn::Get(job, "unitKind");
            const Json& lensFile = Dyn::At(job, "lensFile");
            const std::int64_t turns = kind == "whole" ? 40 : kind == "slot" ? 10 : lensFile == FunctionalLens ? 25
                                     : unitKind == "code" ? 10 : (lensFile == FactsLens || lensFile == "facts.md" ? 12 : 8);
            if (seen.insert({lens, kind}).second) cacheWrite += prefix + lensTokens;
            cacheWrite += tail + static_cast<double>(turns * 3000);
            std::vector<double> reads;
            for (std::int64_t i = 0; i < turns; ++i) reads.push_back(prefix + lensTokens + tail + static_cast<double>(3000 * i));
            cacheRead += Dyn::Sum(reads);
            output += static_cast<double>(turns * outPerTurn);
            ++processes;
        }
        const double costUnits = 1.25 * cacheWrite + 0.1 * cacheRead + 5.0 * output;
        const double listUsd = Dyn::Round((6.25 * cacheWrite + 0.5 * cacheRead + 25.0 * output) / 1e6, 2);
        return {
            {"cacheRead", cacheRead},
            {"cacheWrite", cacheWrite},
            {"output", output},
            {"processes", processes},
            {"costUnits", costUnits},
            {"listUsd", listUsd},
        };
    }
}