import * as fs from "node:fs";
import * as path from "node:path";

export interface SessionSummary {
	name: string;
	firstPrompt: string;
	lastUserPrompt: string;
	recentEdits: string[];
	recentBash: string[];
	lastAssistantNote: string;
	entryCount: number;
	truncated: boolean;
}

/**
 * Candidate session-dir paths for a worktree path. Learns the exact name encoding from a
 * known (dirName ↔ cwd) example when provided, with documented-format fallbacks and a
 * root scan as last resort.
 */
export function sessionDirsForPath(
	target: string,
	root: string,
	known?: { sessionDir: string; cwd: string },
): string[] {
	const enc = target.replace(/\//g, "-");
	const candidates = new Set<string>([`--${enc}--`, `-${enc}-`, enc]);
	if (known) {
		const ownBase = path.basename(known.sessionDir);
		const ownEnc = known.cwd.replace(/\//g, "-");
		const idx = ownBase.indexOf(ownEnc);
		if (idx >= 0) candidates.add(ownBase.slice(0, idx) + enc + ownBase.slice(idx + ownEnc.length));
	}
	const hits: string[] = [];
	for (const c of candidates) {
		const p = path.join(root, c);
		if (fs.existsSync(p)) hits.push(p);
	}
	if (hits.length === 0) {
		try {
			for (const d of fs.readdirSync(root)) if (d.includes(enc)) hits.push(path.join(root, d));
		} catch {}
	}
	return hits;
}

/**
 * Duck-typed summary of a session JSONL without loading it into LLM context.
 * Large files are read as head (~128KB) + tail (~1MB): first prompt and early session
 * names come from the head; recent activity from the tail.
 */
export function summarizeSessionJsonl(file: string): SessionSummary | null {
	let raw = "";
	let truncated = false;
	try {
		const stat = fs.statSync(file);
		if (stat.size > 2_000_000) {
			truncated = true;
			const headLen = 131_072;
			const tailLen = 1_000_000;
			const fd = fs.openSync(file, "r");
			const headBuf = Buffer.alloc(headLen);
			fs.readSync(fd, headBuf, 0, headLen, 0);
			const tailBuf = Buffer.alloc(tailLen);
			fs.readSync(fd, tailBuf, 0, tailLen, stat.size - tailLen);
			fs.closeSync(fd);
			let head = headBuf.toString("utf-8");
			head = head.slice(0, head.lastIndexOf("\n") + 1);
			let tail = tailBuf.toString("utf-8");
			tail = tail.slice(tail.indexOf("\n") + 1);
			raw = head + tail;
		} else {
			raw = fs.readFileSync(file, "utf-8");
		}
	} catch {
		return null;
	}
	const out: SessionSummary = {
		name: "",
		firstPrompt: "",
		lastUserPrompt: "",
		recentEdits: [],
		recentBash: [],
		lastAssistantNote: "",
		entryCount: 0,
		truncated,
	};
	for (const line of raw.split("\n")) {
		if (!line.trim()) continue;
		let e: any;
		try {
			e = JSON.parse(line);
		} catch {
			continue;
		}
		out.entryCount++;
		if (e?.type === "session_info" && typeof e.name === "string" && e.name) out.name = e.name;
		if (e?.type !== "message") continue;
		const m = e.message ?? {};
		const blocks: any[] = Array.isArray(m.content)
			? m.content
			: typeof m.content === "string"
				? [{ type: "text", text: m.content }]
				: [];
		if (m.role === "user") {
			const t = blocks
				.filter((b) => b?.type === "text")
				.map((b) => b.text)
				.join("\n")
				.trim();
			if (t && !t.includes("[[AGENT-COMM]]")) {
				out.lastUserPrompt = t;
				if (!out.firstPrompt) out.firstPrompt = t;
			}
		} else if (m.role === "assistant") {
			for (const b of blocks) {
				if (b?.type === "toolCall") {
					const a = b.arguments ?? {};
					if ((b.name === "edit" || b.name === "write") && (a.file_path ?? a.path)) {
						out.recentEdits.push(a.file_path ?? a.path);
					} else if (b.name === "bash" && typeof a.command === "string") {
						out.recentBash.push(a.command);
					}
				} else if (b?.type === "text" && b.text?.trim()) {
					out.lastAssistantNote = b.text.trim();
				}
			}
		}
	}
	out.recentEdits = [...new Set(out.recentEdits)].slice(-10);
	out.recentBash = out.recentBash.slice(-5);
	return out;
}

/** Extract recent activity from in-memory session branch entries (same duck-typing). */
export function activityFromEntries(entries: any[]): {
	lastUserPrompt: string;
	recentEdits: { tool: string; file?: string }[];
	recentBash: string[];
	lastAssistantNote: string;
} {
	const out = {
		lastUserPrompt: "",
		recentEdits: [] as { tool: string; file?: string }[],
		recentBash: [] as string[],
		lastAssistantNote: "",
	};
	for (const entry of entries ?? []) {
		if (entry?.type !== "message") continue;
		const m = entry.message ?? {};
		const blocks: any[] = Array.isArray(m.content) ? m.content : [];
		if (m.role === "user") {
			const text = blocks
				.filter((b) => b?.type === "text")
				.map((b) => b.text)
				.join("\n")
				.trim();
			if (text && !text.includes("[[AGENT-COMM]]")) out.lastUserPrompt = text;
		} else if (m.role === "assistant") {
			for (const b of blocks) {
				if (b?.type === "toolCall") {
					const args = b.arguments ?? {};
					if (b.name === "edit" || b.name === "write") {
						out.recentEdits.push({ tool: b.name, file: args.file_path ?? args.path ?? args.filePath });
					} else if (b.name === "bash" && typeof args.command === "string") {
						out.recentBash.push(args.command);
					}
				} else if (b?.type === "text" && b.text?.trim()) {
					out.lastAssistantNote = b.text.trim();
				}
			}
		}
	}
	out.recentEdits = out.recentEdits.slice(-15);
	out.recentBash = out.recentBash.slice(-10);
	return out;
}