nixpkgs/modules/home-manager/coding/agents/claude-code.nix

{
  config,
  lib,
  pkgs,
  ...
}:
with lib; let
  cfg = config.coding.agents.claude-code;
  mcpCfg = config.programs.mcp or null;
in {
  options.coding.agents.claude-code = {
    enable = mkEnableOption "Claude Code agent management via canonical agent.toml definitions";

    agentsInput = mkOption {
      type = types.nullOr types.anything;
      default = null;
      description = ''
        The `agents` flake input (your personal AGENTS repo).
        When set, agents are rendered from canonical agent.toml files
        and symlinked to ~/.claude/agents/.
      '';
    };

    modelOverrides = mkOption {
      type = types.attrsOf types.str;
      default = {};
      description = ''
        Per-agent model overrides. Maps agent slug to model alias or ID.
        Example: { chiron = "claude-sonnet-4-20250514"; }
      '';
      example = literalExpression ''
        {
          chiron = "claude-sonnet-4-20250514";
          "chiron-forge" = "claude-sonnet-4-20250514";
        }
      '';
    };

    externalSkills = mkOption {
      type = types.listOf (types.submodule {
        options = {
          src = mkOption {
            type = types.anything;
            description = "Flake input pointing to a skills repository root.";
          };
          skillsDir = mkOption {
            type = types.str;
            default = "skills";
            description = ''
              Subdirectory inside src that contains skill folders.
            '';
          };
          selectSkills = mkOption {
            type = types.nullOr (types.listOf types.str);
            default = null;
            description = ''
              List of skill names to cherry-pick from this source.
              null means include every skill found in skillsDir.
            '';
          };
        };
      });
      default = [];
      description = ''
        External skill sources passed to mkOpencodeSkills.
        Each entry maps directly to an element of the externalSkills
        list accepted by the AGENTS flake's lib.mkOpencodeSkills.
      '';
      example = literalExpression ''
        [
          { src = inputs.skills-anthropic; selectSkills = [ "claude-api" ]; }
          { src = inputs.skills-vercel; }
        ]
      '';
    };

    mcpServers = mkOption {
      type = types.attrsOf types.anything;
      default = if mcpCfg != null then mcpCfg.servers else {};
      defaultText = literalExpression "config.programs.mcp.servers";
      description = ''
        MCP server configurations for Claude Code.
        Merged into ~/.claude/settings.json alongside permissions.
        Automatically inherits from config.programs.mcp.servers.
      '';
    };
  };

  config = mkIf cfg.enable (let
    agentsLib = (import ../../../../lib {inherit lib;}).agents;

    # Rendered agents + permissions (only if agentsInput is set)
    rendered = mkIf (cfg.agentsInput != null) (
      agentsLib.renderForClaudeCode {
        inherit pkgs;
        canonical = cfg.agentsInput.lib.loadAgents;
        modelOverrides = cfg.modelOverrides;
      }
    );

    # Merge MCP servers into the rendered settings.json.
    # The renderer produces { permissions: { allow, deny } }.
    # We add mcpServers on top.
    settingsJson =
      if cfg.agentsInput != null
      then let
        renderedSettings = builtins.fromJSON (builtins.readFile "${rendered}/.claude/settings.json");
        withMcp =
          if cfg.mcpServers != {}
          then renderedSettings // {mcpServers = cfg.mcpServers;}
          else renderedSettings;
      in
        pkgs.writeText "claude-settings.json" (builtins.toJSON withMcp)
      else if cfg.mcpServers != {}
      then pkgs.writeText "claude-settings.json" (builtins.toJSON {mcpServers = cfg.mcpServers;})
      else null;
  in {
    # Rendered agent files symlinked to ~/.claude/agents/
    home.file.".claude/agents" = mkIf (cfg.agentsInput != null) {
      source = "${rendered}/.claude/agents";
    };

    # Skills (merged from personal AGENTS repo + optional external skills)
    home.file.".claude/skills" = mkIf (cfg.agentsInput != null) {
      source = cfg.agentsInput.lib.mkOpencodeSkills {
        inherit pkgs;
        customSkills = "${cfg.agentsInput}/skills";
        externalSkills =
          map (
            entry:
              {inherit (entry) src skillsDir;}
              // optionalAttrs (entry.selectSkills != null) {inherit (entry) selectSkills;}
          )
          cfg.externalSkills;
      };
    };

    # Rendered settings.json with permissions + MCP servers
    home.file.".claude/settings.json" = mkIf (settingsJson != null) {
      source = "${settingsJson}";
    };
  });
}