{
  config,
  lib,
  pkgs,
  ...
}:
with lib; let
  cfg = config.coding.opencode;
in {
  options.coding.opencode = {
    enable = mkEnableOption "opencode AI coding assistant";

    agentsInput = mkOption {
      type = types.nullOr types.anything;
      default = null;
      description = ''
        The `agents` flake input (your personal AGENTS repo).
        When set, skills, context, commands, prompts and the agents.json
        are all symlinked from this input.
      '';
    };

    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; }
        ]
      '';
    };

    ohMyOpencodeSettings = mkOption {
      type = types.attrs;
      default = {};
      description = ''
        Attributes merged (via recursiveUpdate) on top of the default
        oh-my-opencode.json. Use this to set provider-specific model
        assignments per machine.
      '';
      example = literalExpression ''
        {
          agents.sisyphus.model = "anthropic/claude-opus-4-5";
          categories.ultrabrain.model = "anthropic/claude-opus-4-5";
        }
      '';
    };

    extraSettings = mkOption {
      type = types.attrs;
      default = {};
      description = ''
        Extra opencode settings merged (via mkMerge) into
        programs.opencode.settings. Use this to add provider
        configuration that is specific to a machine or organisation.
      '';
      example = literalExpression ''
        {
          provider.anthropic = {
            name = "Anthropic";
            models."claude-opus-4-5" = { limit.context = 200000; };
          };
        }
      '';
    };

    extraPlugins = mkOption {
      type = types.listOf types.str;
      default = [];
      description = ''
        Additional opencode plugins to add to the plugin list.
        Each entry is a path or package name passed to opencode's plugin array.
      '';
    };
  };

  config = mkIf cfg.enable {
    # --- Skills (merged from personal AGENTS repo + optional external skills) ---
    xdg.configFile."opencode/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;
      };
    };

    # --- Static config dirs from AGENTS repo ---
    xdg.configFile."opencode/context" = mkIf (cfg.agentsInput != null) {
      source = "${cfg.agentsInput}/context";
    };
    xdg.configFile."opencode/commands" = mkIf (cfg.agentsInput != null) {
      source = "${cfg.agentsInput}/commands";
    };
    xdg.configFile."opencode/prompts" = mkIf (cfg.agentsInput != null) {
      source = "${cfg.agentsInput}/prompts";
    };

    # --- Core opencode program settings ---
    programs.opencode = {
      enable = true;
      enableMcpIntegration = true;
      settings = mkMerge [
        {
          theme = "opencode";
          plugin = ["oh-my-opencode"] ++ cfg.extraPlugins;
          formatter = {
            alejandra = {
              command = ["alejandra" "-q" "-"];
              extensions = [".nix"];
            };
          };
        }
        # Load agents.json from AGENTS repo when available
        (mkIf (cfg.agentsInput != null) {
          agent = builtins.fromJSON (builtins.readFile "${cfg.agentsInput}/agents/agents.json");
        })
        # Machine/org-specific provider config
        cfg.extraSettings
      ];
    };

    # --- oh-my-opencode plugin config ---
    # Base defaults (no models — those must be set per machine via ohMyOpencodeSettings)
    home.file.".config/opencode/oh-my-opencode.json".text = builtins.toJSON (
      recursiveUpdate
      {
        "$schema" = "https://raw.githubusercontent.com/code-yeongyu/oh-my-opencode/master/assets/oh-my-opencode.schema.json";
        google_auth = false;
        disabled_mcps = ["context7" "websearch"];
      }
      cfg.ohMyOpencodeSettings
    );
  };
}