import type { Database } from "bun:sqlite";
import { inflateSync } from "node:zlib";
import { mirrorState } from "./store.ts";

export type Save = {
	id: string;
	parent: string;
	message: string;
	created_at: number;
	machine: string;
	agent: string;
	session: string;
	is_checkpoint: boolean;
};

export type FileEntry = { path: string; hash: string; executable: boolean; size: number };

export type RepoStats = { saves: number; lines: number; language: string; updated: number | null };

const SAVE_COLUMNS = `id, COALESCE(parent, '') AS parent, message, created_at, machine,
	COALESCE(agent, '') AS agent, COALESCE(session, '') AS session, is_checkpoint = 1 AS is_checkpoint`;
const ID_PREFIX = /^[0-9a-f]{6,12}$/;

// Checkpoints are working marks, not history (§21.4): every list and count below leaves them out.
const NOT_CHECKPOINT = "is_checkpoint = 0";

export function headId(db: Database): string | null {
	return mirrorState(db, "head");
}

/** A page of saves, newest first. Rows land oldest first, so rowid is the order of the line. */
export function history(db: Database, limit: number, offset: number): Save[] {
	return db
		.query<Save, [number, number]>(
			`SELECT ${SAVE_COLUMNS} FROM saves WHERE ${NOT_CHECKPOINT} ORDER BY rowid DESC LIMIT ? OFFSET ?`,
		)
		.all(limit, offset)
		.map(asSave);
}

/** Every save, oldest first, for the timeline. */
export function timeline(db: Database): Save[] {
	return db
		.query<Save, []>(`SELECT ${SAVE_COLUMNS} FROM saves WHERE ${NOT_CHECKPOINT} ORDER BY rowid`)
		.all()
		.map(asSave);
}

/** The save a unique prefix of 6–12 hex characters names (§6.1), or null when none or several do. */
export function saveByPrefix(db: Database, prefix: string): Save | null {
	if (!ID_PREFIX.test(prefix)) return null;
	const rows = db
		.query<Save, [string]>(`SELECT ${SAVE_COLUMNS} FROM saves WHERE id LIKE ? || '%' LIMIT 2`)
		.all(prefix);
	return rows.length === 1 ? asSave(rows[0] as Save) : null;
}

export function filesAt(db: Database, saveId: string): FileEntry[] {
	return db
		.query<FileEntry, [string]>(
			`SELECT f.path, f.hash, f.executable = 1 AS executable, o.size FROM save_files f
			JOIN objects o ON o.hash = f.hash WHERE f.save_id = ? ORDER BY f.path`,
		)
		.all(saveId)
		.map((file) => ({ ...file, executable: Boolean(file.executable) }));
}

export function fileAt(db: Database, saveId: string, path: string): FileEntry | null {
	const file = db
		.query<FileEntry, [string, string]>(
			`SELECT f.path, f.hash, f.executable = 1 AS executable, o.size FROM save_files f
			JOIN objects o ON o.hash = f.hash WHERE f.save_id = ? AND f.path = ?`,
		)
		.get(saveId, path);
	return file ? { ...file, executable: Boolean(file.executable) } : null;
}

export function objectBytes(db: Database, hash: string): Uint8Array | null {
	const row = db
		.query<{ data: Uint8Array }, [string]>("SELECT data FROM objects WHERE hash = ?")
		.get(hash);
	return row ? new Uint8Array(inflateSync(row.data)) : null;
}

export function repoStats(db: Database): RepoStats {
	const row = db
		.query<{ saves: number; updated: number | null }, []>(
			`SELECT COUNT(*) AS saves, MAX(created_at) AS updated FROM saves WHERE ${NOT_CHECKPOINT}`,
		)
		.get() ?? { saves: 0, updated: null };
	return {
		saves: row.saves,
		updated: row.updated,
		lines: Number(mirrorState(db, "lines") ?? 0),
		language: mirrorState(db, "language") ?? "",
	};
}

function asSave(row: Save): Save {
	return { ...row, is_checkpoint: Boolean(row.is_checkpoint) };
}