import { z } from "zod";
import type { AgentDefinition, ToolDefinition } from "../types/index.js";

export interface SummonCallbacks {
	spawn(options: {
		task: string;
		tools: string[];
		workingDirectory?: string;
		/**
		 * Optional slug of an `AgentDefinition` (loaded from
		 * `~/.config/dispatch/agents/` or `<projectDir>/.dispatch/agents/`)
		 * to use as the basis for the spawned child. When provided,
		 * the definition's tools, models, and cwd override the
		 * `tools` and `workingDirectory` parameters passed alongside.
		 */
		agentSlug?: string;
		/**
		 * When true, spawn the agent as an independent top-level "user
		 * agent" tab (no parent, persistent, fire-and-forget) instead of
		 * a subagent child tab. Only honoured when the spawning agent has
		 * the `perm_user_agent` permission.
		 */
		topLevel?: boolean;
	}): Promise<string>;
	getResult(
		agentId: string,
	): Promise<{ status: "done"; result: string } | { status: "error"; error: string }>;
}

/**
 * Summary of an agent definition surfaced to the calling LLM in the
 * summon tool's description. The shape is intentionally minimal — full
 * TOML inspection is done by reading the definition file directly,
 * which all agents are allowed to do by default.
 */
export interface AvailableAgent {
	slug: string;
	name: string;
	description: string;
	/** Filesystem path of the TOML the agent can read for full details. */
	path: string;
}

/**
 * Render a labelled list of agents. Returns an empty array when there
 * are no agents so callers can omit the group entirely.
 */
function renderAgentGroup(label: string, agents: AvailableAgent[]): string[] {
	if (agents.length === 0) return [];
	const lines: string[] = [label];
	for (const a of agents) {
		const desc = a.description ? ` — ${a.description}` : "";
		lines.push(`  - ${a.slug}: ${a.name}${desc}`);
	}
	return lines;
}

/**
 * Build the prose paragraph that lists available agent definitions plus
 * the disk locations where they live, injected into the summon tool's
 * description.
 *
 * `subagentEnabled` and `userAgentEnabled` independently control which
 * groups are shown — they mirror the `perm_summon` and `perm_user_agent`
 * permissions respectively:
 *   - subagents only → generic "Available agents" heading;
 *   - user agents only → a single user-agent group (top_level is implied);
 *   - both → two labelled groups so the LLM understands which slugs
 *     require `top_level=true`.
 *
 * Returns a compact "no agents defined" notice when nothing is visible.
 */
function buildAgentsCatalog(
	subagents: AvailableAgent[],
	userAgents: AvailableAgent[],
	agentDirs: string[],
	userAgentEnabled: boolean,
	subagentEnabled: boolean,
): string {
	const lines: string[] = [];
	lines.push("");
	lines.push("Agent definitions live on disk and can be inspected with read_file/list_files:");
	for (const d of agentDirs) {
		lines.push(`  - ${d}`);
	}

	const visibleSubagents = subagentEnabled ? subagents : [];
	const visibleUserAgents = userAgentEnabled ? userAgents : [];
	if (visibleSubagents.length === 0 && visibleUserAgents.length === 0) {
		lines.push("");
		lines.push("No agent definitions are currently defined.");
		return lines.join("\n");
	}

	lines.push("");
	lines.push("To summon a specific agent, pass its slug as the 'agent' parameter.");
	lines.push("When 'agent' is set, the child inherits that definition's tools, models,");
	lines.push("and working directory; the 'tools' parameter is ignored.");
	lines.push("");

	// User-agent-only mode: list just the user agents. top_level is implied
	// (it is the only thing this grant can spawn), so the heading omits it.
	if (!subagentEnabled && userAgentEnabled) {
		lines.push(
			...renderAgentGroup(
				"User agents (spawned as independent top-level tabs):",
				visibleUserAgents,
			),
		);
		return lines.join("\n");
	}

	// Subagent-only mode: single generic heading.
	if (!userAgentEnabled) {
		lines.push(...renderAgentGroup("Available agents:", visibleSubagents));
		return lines.join("\n");
	}

	// Both enabled: two labelled groups.
	const subagentLines = renderAgentGroup("Subagents (spawned as child tabs):", visibleSubagents);
	const userAgentLines = renderAgentGroup(
		"User agents (spawned as independent top-level tabs, requires top_level=true):",
		visibleUserAgents,
	);
	if (subagentLines.length > 0) {
		lines.push(...subagentLines);
	}
	if (userAgentLines.length > 0) {
		if (subagentLines.length > 0) lines.push("");
		lines.push(...userAgentLines);
	}
	return lines.join("\n");
}

/**
 * Factory for the `summon` tool. Accepts a snapshot of agent definitions
 * available at the time the tool is registered so the LLM's view of
 * which agents exist matches what `spawnChildAgent` can actually load.
 *
 * `agentDirs` is the list of filesystem paths the catalog references in
 * its description; this is information-only — the runtime resolves
 * slugs through `loadAgent` independently.
 *
 * `userAgentEnabled` mirrors the `perm_user_agent` permission and
 * `subagentEnabled` mirrors the `perm_summon` permission. They are
 * independent: the tool is registered whenever at least one is granted.
 *   - subagentEnabled only → spawn ordinary subagents (no `top_level`);
 *   - userAgentEnabled only → spawn ONLY top-level user agents
 *     (`top_level` is forced on, the `background` knob is dropped, and
 *     the catalog lists user agents only);
 *   - both → full behavior (subagents plus `top_level` user agents).
 */
export function createSummonTool(
	_defaultWorkingDirectory: string,
	callbacks: SummonCallbacks,
	availableSubagents: AvailableAgent[] = [],
	availableUserAgents: AvailableAgent[] = [],
	agentDirs: string[] = [],
	userAgentEnabled = false,
	subagentEnabled = true,
): ToolDefinition {
	// When only the user-agent permission is granted the tool spawns user
	// agents exclusively: `top_level` is implied (and forced), subagent
	// mechanics (background, retrieve, parallel work) are irrelevant.
	const userAgentOnly = userAgentEnabled && !subagentEnabled;

	const catalog = buildAgentsCatalog(
		availableSubagents,
		availableUserAgents,
		agentDirs,
		userAgentEnabled,
		subagentEnabled,
	);
	const subagentSlugs = availableSubagents.map((a) => a.slug);
	const userAgentSlugs = availableUserAgents.map((a) => a.slug);
	const allSlugs = userAgentOnly
		? userAgentSlugs
		: userAgentEnabled
			? [...subagentSlugs, ...userAgentSlugs]
			: subagentSlugs;

	const toolNamesList = [
		"The 'tools' parameter controls what the child can do. Available tool names:",
		"  - read_file: Read file contents",
		"  - read_file_slice: Read a character-range slice of a single line",
		"  - list_files: List files and directories",
		"  - write_file: Write/edit files",
		"  - run_shell: Execute shell commands",
		"  - search_code: Search the codebase with the cs ranked code-search engine",
		"  - todo: Track work items",
		"  - summon: Spawn its own child agents (enables nesting)",
		"  - retrieve: Collect results from its children (required if summon is given)",
		"  - web_search: Search the web",
		"  - youtube_transcribe: Fetch YouTube video transcripts",
		"  - send_to_tab: Send a message to another tab/agent by its ID",
		"  - read_tab: Read another tab/agent's latest response by its ID",
	];

	const description = userAgentOnly
		? [
				"Spawn an independent top-level user agent to work on a task.",
				"",
				"User agents are first-class top-level tabs with no parent. They are",
				"fire-and-forget: you get an agent_id back but cannot retrieve their result.",
				"The user agent runs in its own tab visible to the user.",
				"",
				...toolNamesList,
				"",
				"The 'agent' parameter is required — every spawned agent must use a definition.",
				"Tools default to the agent definition's tools, intersected with your own tools (you can't grant capabilities you don't have).",
				catalog,
			].join("\n")
		: [
				"Spawn a new child agent to work on a task independently.",
				"",
				"By default, blocks until the child agent finishes and returns the result directly.",
				"Set background=true to return immediately with an agent_id instead — use retrieve to collect the result later.",
				"",
				"The child agent runs in its own tab visible to the user. Use the 'retrieve' tool with the returned agent_id to get the result when needed.",
				"",
				"Pattern for parallel work:",
				"  1. Call summon multiple times with background=true to start several agents",
				"  2. Do your own work or wait",
				"  3. Call retrieve for each agent_id to collect results",
				...(userAgentEnabled
					? [
							"",
							"Set top_level=true to spawn an independent user agent — a first-class",
							"top-level tab with no parent. User agents are fire-and-forget: you get",
							"an agent_id back but cannot retrieve their result. top_level requires an",
							"'agent' definition listed under 'User agents' below.",
						]
					: []),
				"",
				...toolNamesList,
				"",
				"The 'agent' parameter is required — every spawned agent must use a definition.",
				"Tools default to the agent definition's tools, intersected with your own tools (you can't grant capabilities you don't have).",
				catalog,
			].join("\n");

	const parametersShape = {
		task: z
			.string()
			.describe(
				"Detailed instructions for the child agent. Be specific about what it should do and what it should return.",
			),
		agent: z
			.string()
			.describe(
				[
					"Slug of an agent definition to use as the basis for the child agent.",
					"Required. The child inherits the definition's tools, models, and",
					"working directory; the 'tools' parameter only narrows them further.",
					"Inspect the agent directories listed above to discover which slugs",
					"are available and what each one does.",
					allSlugs.length > 0 ? `Available slugs: ${allSlugs.join(", ")}.` : "",
				]
					.filter(Boolean)
					.join(" "),
			),
		// `top_level` is only an explicit choice when BOTH subagents and user
		// agents are available. In user-agent-only mode it is implied (forced
		// on), so the knob is omitted entirely.
		...(userAgentEnabled && !userAgentOnly
			? {
					top_level: z
						.boolean()
						.optional()
						.describe(
							[
								"If true, spawn the agent as an independent top-level user agent tab",
								"instead of a child subagent. User agents have no parent, persist on",
								"their own, and are fire-and-forget (cannot be retrieved). Requires an",
								"'agent' definition listed under 'User agents'. The 'background' option",
								"is ignored when top_level is true.",
							].join(" "),
						),
				}
			: {}),
		tools: z
			.array(
				z.enum([
					"read_file",
					"read_file_slice",
					"list_files",
					"write_file",
					"run_shell",
					"search_code",
					"key_usage",
					"todo",
					"summon",
					"retrieve",
					"web_search",
					"youtube_transcribe",
					"send_to_tab",
					"read_tab",
				]),
			)
			.optional()
			.describe(
				"Tool names to give the child. Defaults to the agent definition's tools. Intersected with the spawning agent's tools (you can't grant capabilities you don't have).",
			),
		working_directory: z
			.string()
			.optional()
			.describe(
				"Absolute path for the child to work in. Defaults to the agent definition's cwd (or the spawning agent's directory).",
			),
		// `background` is meaningless for fire-and-forget user agents, so the
		// knob is omitted in user-agent-only mode.
		...(userAgentOnly
			? {}
			: {
					background: z
						.boolean()
						.optional()
						.describe(
							"If true, returns immediately with an agent_id for later retrieval. If false (default), blocks until the child agent finishes and returns the result directly. Ignored when top_level is true.",
						),
				}),
	};

	return {
		name: "summon",
		description,
		parameters: z.object(parametersShape),
		execute: async (args: Record<string, unknown>): Promise<string> => {
			const task = args.task as string;
			const agentSlug = args.agent as string | undefined;
			const tools = args.tools as string[] | undefined;
			const workingDirectory = args.working_directory as string | undefined;
			const background = (args.background as boolean | undefined) ?? false;
			// User-agent-only mode always spawns top-level user agents. When both
			// capabilities are present the caller chooses via `top_level`. When
			// only subagents are available, top-level spawning is unavailable.
			const topLevel = userAgentOnly
				? true
				: userAgentEnabled
					? ((args.top_level as boolean | undefined) ?? false)
					: false;

			try {
				const agentId = await callbacks.spawn({
					task,
					tools: tools ?? [],
					...(workingDirectory ? { workingDirectory } : {}),
					...(agentSlug ? { agentSlug } : {}),
					...(topLevel ? { topLevel: true } : {}),
				});

				if (topLevel) {
					// User agents are always fire-and-forget — never block on a
					// result and make it explicit that retrieve won't work.
					return [
						`User agent spawned successfully.`,
						`agent_id: ${agentId}`,
						``,
						`The user agent is now working independently in its own top-level tab.`,
						`It is fire-and-forget — you cannot retrieve its result.`,
					].join("\n");
				}

				if (!background) {
					// Block until the child agent completes. Always prefix the
					// result with `agent_id: <uuid>` so the frontend's
					// ToolCallDisplay regex (`agent_id:\s*([a-f0-9-]+)`) can
					// surface the "Open Tab" button for foreground summons too —
					// not just background ones. The child's tab still exists and
					// holds the full conversation, so the user should always be
					// able to open it.
					const result = await callbacks.getResult(agentId);
					if (result.status === "done") {
						return `agent_id: ${agentId}\n\n${result.result}`;
					}
					return `agent_id: ${agentId}\n\nError from child agent: ${result.error}`;
				}

				return [
					`Agent spawned successfully.`,
					`agent_id: ${agentId}`,
					``,
					`The child agent is now working on the task in its own tab.`,
					`Use the retrieve tool with this agent_id to get the result when ready.`,
				].join("\n");
			} catch (err) {
				return `Error spawning agent: ${err instanceof Error ? err.message : String(err)}`;
			}
		},
	};
}

/**
 * Build the `AvailableAgent[]` projection of an `AgentDefinition` list,
 * deriving each entry's readable `path` from its scope+slug.
 */
function toAvailableAgents(
	defs: AgentDefinition[],
	globalDir: string,
	projectDir: string | null,
): AvailableAgent[] {
	return defs.map((d) => {
		const baseDir =
			d.scope === "global"
				? globalDir
				: projectDir
					? `${projectDir.replace(/\/$/, "")}/.dispatch/agents`
					: globalDir;
		return {
			slug: d.slug,
			name: d.name,
			description: d.description,
			path: `${baseDir}/${d.slug}.toml`,
		};
	});
}

/**
 * Subagent definitions (`is_subagent === true`) — spawned as child tabs.
 */
export function toAvailableSubagents(
	defs: AgentDefinition[],
	globalDir: string,
	projectDir: string | null,
): AvailableAgent[] {
	return toAvailableAgents(
		defs.filter((d) => d.is_subagent),
		globalDir,
		projectDir,
	);
}

/**
 * User-agent definitions (`is_subagent !== true`) — spawnable as
 * independent top-level tabs when `perm_user_agent` is granted.
 */
export function toAvailableUserAgents(
	defs: AgentDefinition[],
	globalDir: string,
	projectDir: string | null,
): AvailableAgent[] {
	return toAvailableAgents(
		defs.filter((d) => d.is_subagent !== true),
		globalDir,
		projectDir,
	);
}