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

export module Crafter.Build:Agents;
import std;
namespace fs = std::filesystem;

// Dependency notes. A crafter-build project ships an AGENTS.consumer.md beside
// its project.cpp, written for the agents of the projects that depend on it,
// and crafter-build merges those files into each consumer's AGENTS.md. Without
// that, an agent working on a consumer knows nothing about the libraries it
// builds against unless someone copied the knowledge in by hand, and a copy
// goes stale the moment the library changes.
//
// The consumer writes its own instructions in an AGENTS.template.md beside its
// project.cpp, and every build writes AGENTS.md from that, so AGENTS.md is
// build output and stays out of version control. Kept in a committed
// AGENTS.md instead, as they once were, the notes changed that file whenever
// a dependency changed its own, on builds that changed nothing else, and
// every diff and rebase carried changes nobody had made.
export namespace Crafter {
    struct Configuration;

    // Which dependencies' notes a project's AGENTS.md carries: the value of
    // Configuration::dependencyNotes.
    enum class DependencyNotes {
        // The projects this one builds against, and the projects those build
        // against, all the way down.
        Transitive,
        // Only the projects this one's own configurations and
        // `#pragma crafter dependency` lines name.
        Direct,
        // None: AGENTS.md holds the template's text alone.
        None,
    };

    // One dependency's AGENTS.consumer.md, ready to merge.
    struct DependencyNote {
        // What the comment above the note calls the dependency: its
        // repository's name, or a local project's directory name.
        std::string name;
        // The file's content, without leading blank lines or trailing
        // whitespace. Lines end in LF; the merge writes the line ending the
        // template uses.
        std::string text;
    };

    // `templateMd` with its dependency notes section holding `notes`, in
    // order: AGENTS.md as it reads below the line that says a build wrote it.
    // A template without a section gets one appended after a blank line; one
    // with a section, which is how a template places it, has it rewritten
    // where it stands, whatever it held; and empty `notes` remove it.
    // Removing a section that ends the template takes the blank line in front
    // of it too, so the result ends as the text before it did. The section
    // uses the template's line ending, so a CRLF file stays CRLF.
    //
    // The two marker lines count only as whole lines outside fenced code
    // blocks, which is what lets a document quote them. Throws, naming the
    // line, when there are notes to write and the markers are unbalanced, or
    // when the section would have to be appended to a template that ends
    // inside a code block: a lone or doubled marker is a slip in the
    // template, and any guess at what it meant would put the notes, or cut
    // the text, where its author did not, while notes appended inside a code
    // block would read as code. With no notes it never throws, since nothing
    // has to be placed. Also throws for a note that would break the section
    // for whoever reads it: one with a marker line of its own, or a code
    // block it never closes.
    std::string MergeDependencyNotes(std::string_view templateMd, std::span<const DependencyNote> notes);

    // Write the AGENTS.md beside `projectFile` from the AGENTS.template.md
    // beside it, with the AGENTS.consumer.md of every dependency
    // project.dependencyNotes selects merged in. `project` is the
    // Configuration that file returned, after LoadProject: loading is what
    // found the dependencies. Creates AGENTS.md when it is missing, and
    // replaces only one a build wrote: an AGENTS.md someone wrote is left
    // alone, with a warning. Without a template it writes nothing, and only
    // warns about a section an earlier crafter-build left in AGENTS.md.
    // Writes only when the text changes, in place, so hard links, ownership
    // and a read-only AGENTS.md are respected; returns whether it wrote. A
    // read or write that fails, a template the notes cannot be placed in and
    // a dependency's unusable notes are warnings: the notes never fail a
    // build, and nothing is reported when nothing would have been written.
    bool UpdateAgentsMd(const Configuration& project, const fs::path& projectFile);
}