// 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 keeps those files in 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.
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. A section an earlier build wrote is removed.
        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
        // document uses.
        std::string text;
    };

    // `agentsMd` with its dependency notes section holding `notes`, in order.
    // A document without a section gets one appended after a blank line; one
    // with a section has it rewritten in place, wherever it was moved to; and
    // empty `notes` remove it. Removing a section that ends the document takes
    // the blank line in front of it too, so a document that ended in a newline
    // before it gained the section gets its own bytes back. The section uses
    // the document'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 document that ends
    // inside a code block: guessing which part of someone's file is generated
    // would overwrite their text, and missing the section would add another on
    // every build. With no notes it never throws, since leaving the document
    // alone loses nothing. Also throws for a note that would break the section
    // when it is read back: one with a marker line of its own, or a code block
    // it never closes.
    std::string MergeDependencyNotes(std::string_view agentsMd, std::span<const DependencyNote> notes);

    // Refresh the dependency notes section of the AGENTS.md beside
    // `projectFile` from the AGENTS.consumer.md of every dependency
    // project.dependencyNotes selects. `project` is the Configuration that
    // file returned, after LoadProject: loading is what found the
    // dependencies. Does nothing when there is no AGENTS.md, which is never
    // created. 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 section that cannot be placed 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);
}