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

module;
export module Crafter.Build:Lint_impl;
import std;
import :Lint;
import :Clang;
import :Platform;
import :Progress;
namespace fs = std::filesystem;
using namespace Crafter;

namespace {
    // Blank //-comments, /*...*/ comments and string/char literal bodies to
    // spaces while copying '\n' through, so byte offsets and line numbers in
    // the result match the original text. Raw string literals are not
    // recognized (documented v1 limitation) — their bodies pass through as
    // ordinary string content until the first '"'.
    std::string StripComments(std::string_view src) {
        enum class State { Code, LineComment, BlockComment, String, Char };
        std::string out;
        out.reserve(src.size());
        State state = State::Code;
        for (std::size_t i = 0; i < src.size(); ++i) {
            char c = src[i];
            char next = i + 1 < src.size() ? src[i + 1] : '\0';
            switch (state) {
                case State::Code:
                    if (c == '/' && next == '/') {
                        state = State::LineComment;
                        out += "  ";
                        ++i;
                    } else if (c == '/' && next == '*') {
                        state = State::BlockComment;
                        out += "  ";
                        ++i;
                    } else if (c == '"') {
                        state = State::String;
                        out += c; // keep the delimiter so quoting stays visible
                    } else if (c == '\'') {
                        state = State::Char;
                        out += c;
                    } else {
                        out += c;
                    }
                    break;
                case State::LineComment:
                    if (c == '\n') {
                        state = State::Code;
                        out += c;
                    } else {
                        out += ' ';
                    }
                    break;
                case State::BlockComment:
                    if (c == '*' && next == '/') {
                        state = State::Code;
                        out += "  ";
                        ++i;
                    } else {
                        out += c == '\n' ? '\n' : ' ';
                    }
                    break;
                case State::String:
                case State::Char: {
                    char delim = state == State::String ? '"' : '\'';
                    if (c == '\\' && next != '\0') {
                        out += "  ";
                        ++i;
                        if (next == '\n') out.back() = '\n';
                    } else if (c == delim) {
                        state = State::Code;
                        out += c;
                    } else {
                        out += c == '\n' ? '\n' : ' ';
                    }
                    break;
                }
            }
        }
        return out;
    }

    std::vector<std::string_view> SplitLines(std::string_view content) {
        std::vector<std::string_view> lines;
        std::size_t start = 0;
        while (start <= content.size()) {
            std::size_t end = content.find('\n', start);
            if (end == std::string_view::npos) {
                // Skip a phantom empty final line after a trailing '\n'.
                if (start < content.size()) lines.push_back(content.substr(start));
                break;
            }
            lines.push_back(content.substr(start, end - start));
            start = end + 1;
        }
        return lines;
    }

    bool PathInsideRoot(const fs::path& p, const fs::path& root) {
        fs::path rel = fs::weakly_canonical(p).lexically_relative(fs::weakly_canonical(root));
        return !rel.empty() && *rel.begin() != "..";
    }

    // Depth-first walk over the dependency graph keeping only Configurations
    // whose path lies inside the project root — GitProject / external deps
    // live under the global cache and are foreign code: they contribute
    // neither rules nor files. Root-first order so the root's rules win the
    // by-name dedup.
    std::vector<Configuration*> CollectLocalConfigs(Configuration& root, const fs::path& projectRoot) {
        std::vector<Configuration*> local;
        std::unordered_set<Configuration*> seen;
        std::function<void(Configuration*)> walk = [&](Configuration* c) {
            if (!seen.insert(c).second) return;
            if (PathInsideRoot(fs::absolute(c->path), projectRoot)) {
                local.push_back(c);
            }
            for (Configuration* dep : c->dependencies) walk(dep);
        };
        walk(&root);
        return local;
    }

    void CollectConfigSources(const Configuration& c, std::set<fs::path>& files) {
        for (const std::unique_ptr<Module>& mod : c.interfaces) {
            files.insert(fs::path(std::format("{}.cppm", mod->path.string())));
            for (const std::unique_ptr<ModulePartition>& part : mod->partitions) {
                files.insert(fs::path(std::format("{}.cppm", part->path.string())));
            }
        }
        for (const Implementation& impl : c.implementations) {
            files.insert(fs::path(std::format("{}.cpp", impl.path.string())));
        }
        // cFiles/cuda resolve against cwd at build time (see Build's compile
        // loops); mirror that here.
        for (const fs::path& cf : c.cFiles) {
            files.insert(fs::absolute(fs::path(std::format("{}.c", cf.string()))).lexically_normal());
        }
        for (const fs::path& cu : c.cuda) {
            files.insert(fs::absolute(fs::path(std::format("{}.cu", cu.string()))).lexically_normal());
        }
        for (const Shader& shader : c.shaders) {
            files.insert(fs::absolute(shader.path).lexically_normal());
        }
        // files/buildFiles/assets are deliberately excluded: data shipped or
        // referenced by the build, not source code.
    }
}

std::string LintContext::Extension() const {
    return file.extension().string();
}

std::string_view LintContext::Line(std::size_t n) const {
    if (n == 0 || n > lines.size()) return {};
    return lines[n - 1];
}

const std::string& LintContext::CommentStripped() {
    if (!commentStrippedCache) {
        commentStrippedCache = StripComments(content);
    }
    return *commentStrippedCache;
}

void LintContext::Report(std::size_t line, std::string message) {
    sink->push_back({file, line, activeRule, std::move(message)});
}

namespace {
    // Scan raw lines for suppression comments. Raw, not stripped: the
    // directives ARE comments. A next-line directive on (0-based) line i
    // targets 1-based line i + 2 — the line below it.
    LintSuppressions ParseSuppressions(std::span<const std::string_view> lines) {
        LintSuppressions s;
        constexpr std::string_view NextLineMarker = "lint-disable-next-line";
        constexpr std::string_view FileMarker = "lint-disable-file";
        for (std::size_t i = 0; i < lines.size(); ++i) {
            std::size_t slash = lines[i].find("//");
            if (slash == std::string_view::npos) continue;
            bool nextLine = true;
            std::size_t marker = lines[i].find(NextLineMarker, slash);
            std::size_t markerLen = NextLineMarker.size();
            if (marker == std::string_view::npos) {
                nextLine = false;
                marker = lines[i].find(FileMarker, slash);
                markerLen = FileMarker.size();
            }
            if (marker == std::string_view::npos) continue;
            // Everything after the marker is rule names; none = all rules.
            std::string_view rest = lines[i].substr(marker + markerLen);
            std::vector<std::string> names;
            std::size_t pos = 0;
            while (pos < rest.size()) {
                if (rest[pos] == ' ' || rest[pos] == '\t' || rest[pos] == ',' || rest[pos] == '\r') { ++pos; continue; }
                std::size_t end = rest.find_first_of(" \t,\r", pos);
                if (end == std::string_view::npos) end = rest.size();
                names.emplace_back(rest.substr(pos, end - pos));
                pos = end;
            }
            if (nextLine) {
                if (names.empty()) s.lineAll.insert(i + 2);
                else for (std::string& n : names) s.lineRules[i + 2].insert(std::move(n));
            } else {
                if (names.empty()) s.fileAll = true;
                else for (std::string& n : names) s.fileRules.insert(std::move(n));
            }
        }
        return s;
    }
}

bool LintContext::Suppressed(std::string_view rule, std::size_t line) {
    if (!suppressionsCache) suppressionsCache = ParseSuppressions(lines);
    const LintSuppressions& s = *suppressionsCache;
    if (s.fileAll || s.fileRules.contains(std::string(rule))) return true;
    if (line == 0) return false;
    if (s.lineAll.contains(line)) return true;
    if (auto it = s.lineRules.find(line); it != s.lineRules.end()) return it->second.contains(std::string(rule));
    return false;
}

void LintContext::SetContent(std::string newContent) {
    content = std::move(newContent);
    lines = SplitLines(content);
    commentStrippedCache.reset();
    suppressionsCache.reset(); // line numbers may have shifted — re-parse
}

void Configuration::AddLintRule(std::string name, std::function<void(LintContext&)> check) {
    lintRules.push_back({std::move(name), std::move(check)});
}

LintSummary Crafter::RunLint(Configuration& projectCfg, const RunLintOptions& opts) {
    LintSummary summary;

    fs::path projectRoot = opts.projectFile.empty()
        ? fs::absolute(projectCfg.path)
        : opts.projectFile.parent_path();

    std::vector<Configuration*> localConfigs = CollectLocalConfigs(projectCfg, projectRoot);

    // Collect rules root-first, dedup by name (first registration wins).
    std::vector<const LintRule*> rules;
    std::unordered_set<std::string_view> ruleNames;
    for (Configuration* c : localConfigs) {
        for (const LintRule& rule : c->lintRules) {
            if (ruleNames.insert(rule.name).second) rules.push_back(&rule);
        }
    }

    if (rules.empty()) {
        summary.noRulesDefined = true;
        std::println(std::cerr,
R"msg(No lint rules defined.
Register rules in project.cpp before returning the Configuration:

    cfg.AddLintRule("no-tabs", [](Crafter::LintContext& ctx) {{
        if (ctx.Extension() != ".cpp" && ctx.Extension() != ".cppm") return;
        for (std::size_t n = 1; n <= ctx.lines.size(); ++n) {{
            if (ctx.Line(n).contains('\t')) ctx.Report(n, "tab character (use spaces)");
        }}
    }});

A rule that calls ctx.SetContent(newContent) is a transform: `crafter-build
format` applies it to disk, and `crafter-build lint` reports where it would.
`crafter-build lint` runs every rule over the project's own sources.)msg");
        return summary;
    }

    std::erase_if(rules, [&](const LintRule* r) { return !MatchAny(opts.globs, r->name); });
    summary.rulesRun = rules.size();

    if (opts.listOnly) {
        for (const LintRule* rule : rules) std::println("{}", rule->name);
        return summary;
    }
    if (rules.empty()) {
        std::println("No lint rules matched.");
        return summary;
    }

    std::set<fs::path> files;
    for (Configuration* c : localConfigs) {
        CollectConfigSources(*c, files);
        for (const Test& t : c->tests) CollectConfigSources(t.config, files);
    }
    if (!opts.projectFile.empty()) files.insert(opts.projectFile);

    fs::path cwd = fs::current_path();
    auto shown = [&cwd](const fs::path& p) {
        return PathInsideRoot(p, cwd) ? p.lexically_relative(cwd) : p;
    };

    for (const fs::path& file : files) {
        std::ifstream in(file, std::ios::binary);
        if (!in) continue; // config parse already read it; a vanished file fails the build first
        std::stringstream buffer;
        buffer << in.rdbuf();
        LintContext ctx;
        ctx.file = file;
        ctx.content = std::move(buffer).str();
        ctx.lines = SplitLines(ctx.content);
        ctx.sink = &summary.findings;
        ++summary.filesLinted;
        const std::string original = ctx.content;
        for (const LintRule* rule : rules) {
            ctx.activeRule = rule->name;
            // Snapshot for transform diffing — and the revert point if the
            // rule throws, so a half-applied transform never reaches disk
            // and chained rules see clean input.
            std::string before = ctx.content;
            try {
                rule->check(ctx);
            } catch (const std::exception& e) {
                // Never let a rule's exception unwind across the project
                // DLL boundary — surface it as a finding instead.
                ctx.SetContent(std::move(before));
                ctx.Report(0, std::format("rule '{}' threw: {}", rule->name, e.what()));
                ++summary.errors;
                if (opts.mode != LintMode::Report) {
                    // Report mode prints it with the findings; the other
                    // modes don't print findings, so surface it here.
                    std::println(std::cerr, "{}: rule '{}' threw: {}", shown(file).string(), rule->name, e.what());
                }
                continue;
            }
            // Transform detection is compare-by-value: a rule that SetContents
            // identical bytes is not a change. The mutated content carries
            // forward in every mode so chained rules compose identically
            // whether or not this run writes.
            if (ctx.content == before) continue;
            // File-level suppression disables the transform outright — in
            // every mode, so `format` never rewrites a suppressed file.
            if (ctx.Suppressed(rule->name, 0)) {
                ctx.SetContent(std::move(before));
                continue;
            }
            // Diff before/after. Same line count → per-line handling:
            // suppressed changed lines are REVERTED (all modes — suppression
            // must also stop `format`), the rest yield would-reformat
            // findings in the dry modes. Different count (or no differing
            // line — SplitLines hides a trailing '\n', the final-newline
            // case) → one whole-file finding; count-changing transforms
            // handle per-line suppression themselves (see
            // LintContext::Suppressed).
            std::vector<std::string_view> beforeLines = SplitLines(before);
            bool anyLineDiffers = false;
            if (beforeLines.size() == ctx.lines.size()) {
                std::vector<std::size_t> reverted;
                for (std::size_t i = 0; i < beforeLines.size(); ++i) {
                    if (beforeLines[i] == ctx.lines[i]) continue;
                    anyLineDiffers = true;
                    if (ctx.Suppressed(rule->name, i + 1)) {
                        reverted.push_back(i);
                    } else if (opts.mode != LintMode::Apply) {
                        summary.findings.push_back({file, i + 1, rule->name, "would reformat"});
                    }
                }
                if (!reverted.empty()) {
                    std::string rebuilt;
                    rebuilt.reserve(ctx.content.size());
                    std::size_t next = 0;
                    for (std::size_t i = 0; i < ctx.lines.size(); ++i) {
                        rebuilt += (next < reverted.size() && reverted[next] == i) ? beforeLines[i] : ctx.lines[i];
                        if (next < reverted.size() && reverted[next] == i) ++next;
                        if (i + 1 < ctx.lines.size() || ctx.content.ends_with('\n')) rebuilt += '\n';
                    }
                    ctx.SetContent(std::move(rebuilt));
                }
            }
            if (!anyLineDiffers && opts.mode != LintMode::Apply && ctx.content != before) {
                summary.findings.push_back({file, 0, rule->name, "would reformat"});
            }
        }
        // Drop findings the file's directives suppress — covers Report()
        // calls from any rule (custom ones included) plus the derived
        // would-reformat findings above. Line-0 findings only match
        // file-level directives.
        std::erase_if(summary.findings, [&](const LintFinding& f) {
            return f.file == file && ctx.Suppressed(f.rule, f.line);
        });
        if (ctx.content != original) {
            summary.changedFiles.push_back(file);
            if (opts.mode == LintMode::Apply) {
                std::ofstream out(file, std::ios::binary | std::ios::trunc);
                out.write(ctx.content.data(), static_cast<std::streamsize>(ctx.content.size()));
                out.close();
                if (!out) {
                    std::println(std::cerr, "failed to write {}", shown(file).string());
                    ++summary.errors;
                }
            }
        }
    }

    std::sort(summary.findings.begin(), summary.findings.end(),
              [](const LintFinding& a, const LintFinding& b) {
                  return std::tie(a.file, a.line) < std::tie(b.file, b.line);
              });

    Progress::Clear();
    switch (opts.mode) {
        case LintMode::Report: {
            std::unordered_set<std::string> filesWithFindings;
            for (const LintFinding& f : summary.findings) {
                filesWithFindings.insert(f.file.string());
                std::println("{}:{}: warning: {} [{}]", shown(f.file).string(), f.line, f.message, f.rule);
            }
            if (summary.findings.empty()) {
                std::println("Lint clean: {} files, {} rules", summary.filesLinted, summary.rulesRun);
            } else {
                std::println("{} finding(s) in {} of {} files ({} rules)", summary.findings.size(), filesWithFindings.size(), summary.filesLinted, summary.rulesRun);
            }
            break;
        }
        case LintMode::Check: {
            // gofmt -l style: the paths alone, then a one-line verdict.
            // Report-only findings are lint's business, not printed here.
            for (const fs::path& f : summary.changedFiles) {
                std::println("{}", shown(f).string());
            }
            if (summary.changedFiles.empty()) {
                std::println("Format check clean: {} files, {} rules", summary.filesLinted, summary.rulesRun);
            } else {
                std::println("{} file(s) would be reformatted", summary.changedFiles.size());
            }
            break;
        }
        case LintMode::Apply: {
            for (const fs::path& f : summary.changedFiles) {
                std::println("formatted: {}", shown(f).string());
            }
            if (summary.changedFiles.empty()) {
                std::println("Nothing to format: {} files, {} rules", summary.filesLinted, summary.rulesRun);
            } else {
                std::println("Formatted {} of {} files ({} rules)", summary.changedFiles.size(), summary.filesLinted, summary.rulesRun);
            }
            break;
        }
    }
    return summary;
}