import type { EventFrame } from "./protocol";

// ---------- event list merge ----------

export function mergeEvents(
	existing: EventFrame[],
	incoming: EventFrame[],
): EventFrame[] {
	const bySeq = new Map<number, EventFrame>();
	for (const e of existing) bySeq.set(e.seq, e);
	for (const e of incoming) bySeq.set(e.seq, e);
	return Array.from(bySeq.values()).sort((a, b) => a.seq - b.seq);
}

/** Highest persisted seq — deltas (`message_update`) are not persisted, so they
 *  must not advance the refetch cursor. */
export function lastPersistedSeq(events: EventFrame[]): number {
	let max = 0;
	for (const e of events)
		if (e.type !== "message_update" && e.seq > max) max = e.seq;
	return max;
}

// ---------- chat view derivation ----------

export interface ToolState {
	id: string;
	name: string;
	args: string;
	running: boolean;
	isError: boolean;
	preview: string;
}

export interface ChatMessage {
	key: string;
	role: "user" | "assistant" | "system" | "toolResult";
	text: string;
	thinking: string | null;
	toolCalls: { id: string; name: string; argsJson: string }[];
	toolCallId: string | null;
	streaming: boolean;
	/** envelope ts of the persisted message_end (0 while streaming) */
	ts: number;
	/** true for daemon/plugin error notices: rendered as a notice line, not a chat bubble */
	notice?: boolean;
}

export interface ChatDerivation {
	messages: ChatMessage[];
	tools: Map<string, ToolState>;
	busy: boolean;
	usage: { inputTokens: number; outputTokens: number; totalCost: number };
}

// The plugin mirrors pi extension events verbatim: tool args arrive as a raw
// JSON object (or string in older frames). Normalizing at this boundary keeps
// the render layer string-only; regression: object args crashed React (#31).
export function argsText(args: unknown): string {
	if (typeof args === "string") return args;
	if (args === null || args === undefined) return "";
	try {
		return JSON.stringify(args, null, 2) ?? "";
	} catch {
		return String(args);
	}
}

export function deriveChat(events: EventFrame[]): ChatDerivation {
	const messages: ChatMessage[] = [];
	const tools = new Map<string, ToolState>();
	let stream: { id: string; text: string } | null = null;
	let busy = false;
	const usage = { inputTokens: 0, outputTokens: 0, totalCost: 0 };

	for (const e of events) {
		switch (e.type) {
			case "tool_execution_start": {
				if (e.toolCallId !== undefined) {
					tools.set(e.toolCallId, {
						id: e.toolCallId,
						name: e.toolName ?? "tool",
						args: argsText(e.args),
						running: true,
						isError: false,
						preview: "",
					});
				}
				break;
			}
			case "tool_execution_end": {
				const t =
					e.toolCallId !== undefined ? tools.get(e.toolCallId) : undefined;
				if (t !== undefined) {
					t.running = false;
					t.isError = e.isError ?? false;
					t.preview = e.resultPreview ?? "";
				}
				break;
			}
			case "agent_start":
				busy = true;
				break;
			case "agent_end": {
				const u = e.usage;
				if (u !== undefined) {
					usage.inputTokens += u.inputTokens ?? 0;
					usage.outputTokens += u.outputTokens ?? 0;
					usage.totalCost += u.totalCost ?? 0;
				}
				break;
			}
			case "agent_settled":
				busy = false;
				break;
			case "message_start":
				if (e.message?.role === "assistant")
					stream = { id: e.message.id, text: "" };
				break;
			case "message_update":
				if (stream !== null) stream.text += e.delta ?? "";
				break;
			case "message_end": {
				const m = e.message;
				if (m !== undefined) {
					if (stream !== null && stream.id === m.id) stream = null;
					messages.push({
						key: `msg-${e.seq}`,
						role: m.role,
						text: m.text,
						thinking: m.thinking,
						toolCalls: m.toolCalls ?? [],
						toolCallId: m.toolCallId,
						streaming: false,
						ts: e.ts ?? 0,
					});
				}
				break;
			}
			case "error_notice":
				messages.push({
					key: `notice-${e.seq}`,
					role: "system",
					text: e.reason ?? "unknown error",
					thinking: null,
					toolCalls: [],
					toolCallId: null,
					streaming: false,
					ts: e.ts ?? 0,
					notice: true,
				});
				break;
			default:
				break;
		}
	}

	if (stream !== null) {
		messages.push({
			key: `stream-${stream.id}`,
			role: "assistant",
			text: stream.text,
			thinking: null,
			toolCalls: [],
			toolCallId: null,
			streaming: true,
			ts: 0,
		});
	}

	return { messages, tools, busy: busy || stream !== null, usage };
}

// ---------- todo / subagent derivation (client-side, per PROTOCOL.md) ----------

export type TodoStatus = "pending" | "in-progress" | "completed";

export interface TodoItem {
	content: string;
	status: TodoStatus;
	deleted: boolean;
}

export interface SubagentRun {
	key: string;
	name: string;
	running: boolean;
	isError: boolean;
}

export interface TaskDerivation {
	todos: TodoItem[];
	subagents: SubagentRun[];
	workingTools: ToolState[];
}

const TODO_TOOL = "todo";
const SUBAGENT_TOOL = "subagent";

function parseJson(raw: unknown): unknown {
	if (typeof raw === "object" && raw !== null) return raw; // already-decoded args
	if (typeof raw !== "string" || raw.length === 0) return undefined;
	try {
		return JSON.parse(raw) as unknown;
	} catch {
		return undefined;
	}
}

function normalizeStatus(raw: unknown): TodoStatus {
	if (typeof raw !== "string") return "pending";
	switch (raw.toLowerCase()) {
		case "in_progress":
		case "in-progress":
		case "inprogress":
		case "in progress":
		case "doing":
		case "started":
			return "in-progress";
		case "completed":
		case "complete":
		case "done":
			return "completed";
		default:
			return "pending";
	}
}

function extractSnapshot(
	raw: unknown,
): { content: string; status: TodoStatus }[] | null {
	let arr: unknown = raw;
	if (Array.isArray(raw) === false && raw !== null && typeof raw === "object") {
		const o = raw as Record<string, unknown>;
		const nested = o.todos ?? o.items ?? o.tasks ?? o.list;
		if (Array.isArray(nested)) arr = nested;
	}
	if (Array.isArray(arr) === false) return null;
	const items: { content: string; status: TodoStatus }[] = [];
	for (const entry of arr) {
		if (typeof entry === "string") {
			items.push({ content: entry, status: "pending" });
			continue;
		}
		if (entry !== null && typeof entry === "object") {
			const o = entry as Record<string, unknown>;
			const content = o.content ?? o.title ?? o.text ?? o.subject ?? o.summary;
			if (typeof content === "string" && content.length > 0) {
				items.push({ content, status: normalizeStatus(o.status) });
			}
		}
	}
	return items.length > 0 ? items : null;
}

export function deriveTasks(events: EventFrame[]): TaskDerivation {
	const toolNames = new Map<string, string>(); // toolCallId -> toolName
	for (const e of events) {
		if (e.type === "tool_execution_start" && e.toolCallId !== undefined) {
			toolNames.set(e.toolCallId, e.toolName ?? "");
		}
	}

	// todo snapshots, seq-ordered: args from execution start, result from execution end + toolResult message
	const snapshots: {
		seq: number;
		items: { content: string; status: TodoStatus }[];
	}[] = [];
	const subagents: SubagentRun[] = [];
	const runningTools: ToolState[] = [];

	for (const e of events) {
		if (e.type === "tool_execution_start" && e.toolCallId !== undefined) {
			const name = e.toolName ?? "";
			if (name === TODO_TOOL) {
				const snap = extractSnapshot(parseJson(e.args));
				if (snap !== null) snapshots.push({ seq: e.seq, items: snap });
			} else if (name === SUBAGENT_TOOL) {
				const parsed = parseJson(e.args);
				const o =
					parsed !== null && typeof parsed === "object"
						? (parsed as Record<string, unknown>)
						: {};
				const nameField =
					o.agentName ?? o.agent ?? o.name ?? o.agentType ?? o.role;
				subagents.push({
					key: e.toolCallId,
					name:
						typeof nameField === "string" && nameField.length > 0
							? nameField
							: "subagent",
					running: true,
					isError: false,
				});
			} else {
				runningTools.push({
					id: e.toolCallId,
					name,
					args: argsText(e.args),
					running: true,
					isError: false,
					preview: "",
				});
			}
		} else if (e.type === "tool_execution_end" && e.toolCallId !== undefined) {
			const name = toolNames.get(e.toolCallId) ?? "";
			if (name === SUBAGENT_TOOL) {
				const run = subagents.find((s) => s.key === e.toolCallId);
				if (run !== undefined) {
					run.running = false;
					run.isError = e.isError ?? false;
				}
			} else if (name !== TODO_TOOL) {
				const t = runningTools.find((w) => w.id === e.toolCallId);
				if (t !== undefined) {
					t.running = false;
					t.isError = e.isError ?? false;
					t.preview = e.resultPreview ?? "";
				}
			}
			if (name === TODO_TOOL) {
				const snap = extractSnapshot(parseJson(e.resultPreview));
				if (snap !== null) snapshots.push({ seq: e.seq, items: snap });
			}
		} else if (
			e.type === "message_end" &&
			e.message?.role === "toolResult" &&
			e.message.toolCallId !== null
		) {
			const name = toolNames.get(e.message.toolCallId) ?? "";
			if (name === TODO_TOOL) {
				const snap = extractSnapshot(parseJson(e.message.text));
				if (snap !== null) snapshots.push({ seq: e.seq, items: snap });
			}
		}
	}

	// todos: latest snapshot wins; earlier items missing from it are deleted
	const todos: TodoItem[] = [];
	if (snapshots.length > 0) {
		snapshots.sort((a, b) => a.seq - b.seq);
		const latest = snapshots[snapshots.length - 1]?.items ?? [];
		const seen = new Map<string, TodoStatus>();
		for (const snap of snapshots) {
			for (const item of snap.items)
				if (!seen.has(item.content)) seen.set(item.content, item.status);
		}
		for (const item of latest) {
			todos.push({
				content: item.content,
				status: item.status,
				deleted: false,
			});
			seen.delete(item.content);
		}
		for (const [content] of seen)
			todos.push({ content, status: "pending", deleted: true });
	}

	return {
		todos,
		subagents,
		workingTools: runningTools.filter((t) => t.running),
	};
}