# Harness-agnostic agent management utilities
#
# This module provides functions to load canonical agent definitions and
# render them for different AI coding tools (OpenCode, Claude Code, Pi).
#
# Usage in your configuration:
#
#   # In your flake or configuration:
#   let
#     m3taLib = inputs.m3ta-nixpkgs.lib.${system};
#
#     # Load canonical agents from the AGENTS flake input
#     canonical = m3taLib.agents.loadCanonical { agentsInput = inputs.agents; };
#
#     # Render for a specific tool
#     agentFiles = m3taLib.agents.renderForTool {
#       inherit pkgs;
#       agentsInput = inputs.agents;
#       tool = "opencode";
#     };
#   in { ... }
#
# Renderers are stubs for now (Tasks 9-11 will provide real implementations).
{lib}: let
  agentsLib = {
    # Load canonical agent definitions from the AGENTS flake input.
    # agentsInput: the AGENTS flake (e.g., inputs.agents in a consuming flake)
    # Returns the canonical attrset from lib.loadAgents (keyed by slug).
    loadCanonical = {agentsInput}: agentsInput.lib.loadAgents;

    # OpenCode renderer — produces a directory of .opencode/agents/*.md files.
    # Each file has YAML frontmatter (description, mode, optional model,
    # optional permission) followed by the agent's systemPrompt content.
    renderForOpencode = {
      pkgs,
      canonical,
      modelOverrides ? {},
    }: let
      # Split a rule string on the LAST colon to get { pattern, action }.
      # e.g. "rm -rf *:ask" → pattern="rm -rf *", action="ask"
      # e.g. "/run/agenix/**:deny" → pattern="/run/agenix/**", action="deny"
      parseRule = ruleStr: let
        parts = lib.strings.splitString ":" ruleStr;
        # last element is the action, everything before joined with ":" is pattern
        action = lib.last parts;
        pattern = lib.concatStringsSep ":" (lib.init parts);
      in {inherit pattern action;};

      # Render one permission section to YAML lines (list of strings).
      # intent-only → single line: "  <tool>: <intent>"
      # intent+rules → nested block starting with "*": <intent>, then specific rules
      renderPermSection = tool: section:
        if !(section ? rules) || section.rules == []
        then ["  ${tool}: ${section.intent}"]
        else let
          parsedRules = map parseRule section.rules;
          wildcardLine = "    \"*\": ${section.intent}";
          ruleLines = map (r: "    \"${r.pattern}\": ${r.action}") parsedRules;
        in
          ["  ${tool}:"] ++ [wildcardLine] ++ ruleLines;

      # Render the full permission block for an agent.
      # Returns empty list if no permissions.
      renderPermBlock = permissions:
        if permissions == {} || permissions == null
        then []
        else
          ["permission:"]
          ++ lib.concatLists (
            lib.mapAttrsToList renderPermSection permissions
          );

      # Build the YAML frontmatter string for one agent.
      mkFrontmatter = name: agent: let
        descLine = "description: \"${agent.description}.\"";
        modeLine = "mode: ${agent.mode}";
        modelLine =
          lib.optionalString
          (modelOverrides ? ${name})
          "model: ${modelOverrides.${name}}\n";
        permBlock = renderPermBlock (agent.permissions or {});
        permLines =
          if permBlock == []
          then ""
          else lib.concatStringsSep "\n" permBlock + "\n";
      in "---\n${descLine}\n${modeLine}\n${modelLine}${permLines}---\n";

      # Build the full markdown file content for one agent.
      mkAgentContent = name: agent:
        (mkFrontmatter name agent) + agent.systemPrompt;

      # Write each agent as a derivation text file.
      mkAgentFile = name: agent:
        pkgs.writeText "${name}.md" (mkAgentContent name agent);

      # Attrset of name → derivation for each agent.
      agentFiles = lib.mapAttrs mkAgentFile canonical;

      # Shell commands to copy each file into $out.
      copyCommands = lib.concatStringsSep "\n" (
        lib.mapAttrsToList (name: file: "cp ${file} $out/${name}.md") agentFiles
      );
    in
      pkgs.runCommand "opencode-agents" {} ''
        mkdir -p $out
        ${copyCommands}
      '';

    # Stub: Claude Code renderer — produces .claude/agents/*.md files.
    # To be implemented in Task 10.
    renderForClaudeCode = {
      pkgs,
      canonical,
      modelOverrides ? {},
    }:
      pkgs.runCommand "claude-code-agents" {} "echo stub > $out";

    # Stub: Pi renderer — produces AGENTS.md + SYSTEM.md.
    # To be implemented in Task 11.
    renderForPi = {
      pkgs,
      canonical,
    }:
      pkgs.runCommand "pi-agents" {} "echo stub > $out";

    # Dispatch renderer by tool name.
    # tool: "opencode" | "claude-code" | "pi"
    renderForTool = {
      pkgs,
      agentsInput,
      tool,
      modelOverrides ? {},
    }: let
      canonical = agentsInput.lib.loadAgents;
    in
      if tool == "opencode"
      then
        agentsLib.renderForOpencode {
          inherit pkgs canonical modelOverrides;
        }
      else if tool == "claude-code"
      then
        agentsLib.renderForClaudeCode {
          inherit pkgs canonical modelOverrides;
        }
      else if tool == "pi"
      then agentsLib.renderForPi {inherit pkgs canonical;}
      else throw "lib.agents.renderForTool: unknown tool '${tool}'. Must be opencode, claude-code, or pi.";
  };
in
  agentsLib