import type { Kysely } from "kysely";
import { monotonicFactory } from "ulidx";

import type { Database, RevisionTable } from "../types.js";

const monotonic = monotonicFactory();

export interface Revision {
	id: string;
	collection: string;
	entryId: string;
	data: Record<string, unknown>;
	authorId: string | null;
	createdAt: string;
}

export interface CreateRevisionInput {
	collection: string;
	entryId: string;
	data: Record<string, unknown>;
	authorId?: string;
}

/**
 * Revision repository for version history
 *
 * Each revision stores a JSON snapshot of the content at a point in time.
 * Used when collection has `supports: ["revisions"]` enabled.
 */
export class RevisionRepository {
	constructor(private db: Kysely<Database>) {}

	/**
	 * Create a new revision
	 */
	async create(input: CreateRevisionInput): Promise<Revision> {
		const id = monotonic();

		const row: Omit<RevisionTable, "created_at"> = {
			id,
			collection: input.collection,
			entry_id: input.entryId,
			data: JSON.stringify(input.data),
			author_id: input.authorId ?? null,
		};

		await this.db.insertInto("revisions").values(row).execute();

		const revision = await this.findById(id);
		if (!revision) {
			throw new Error("Failed to create revision");
		}
		return revision;
	}

	/**
	 * Find revision by ID
	 */
	async findById(id: string): Promise<Revision | null> {
		const row = await this.db
			.selectFrom("revisions")
			.selectAll()
			.where("id", "=", id)
			.executeTakeFirst();

		return row ? this.rowToRevision(row) : null;
	}

	/**
	 * Get all revisions for an entry (newest first)
	 *
	 * Orders by monotonic ULID (descending). The monotonic factory
	 * guarantees strictly increasing IDs even within the same millisecond.
	 */
	async findByEntry(
		collection: string,
		entryId: string,
		options: { limit?: number } = {},
	): Promise<Revision[]> {
		let query = this.db
			.selectFrom("revisions")
			.selectAll()
			.where("collection", "=", collection)
			.where("entry_id", "=", entryId)
			.orderBy("id", "desc");

		if (options.limit) {
			query = query.limit(options.limit);
		}

		const rows = await query.execute();
		return rows.map((row) => this.rowToRevision(row));
	}

	/**
	 * Get the most recent revision for an entry
	 */
	async findLatest(collection: string, entryId: string): Promise<Revision | null> {
		const row = await this.db
			.selectFrom("revisions")
			.selectAll()
			.where("collection", "=", collection)
			.where("entry_id", "=", entryId)
			.orderBy("id", "desc")
			.limit(1)
			.executeTakeFirst();

		return row ? this.rowToRevision(row) : null;
	}

	/**
	 * Count revisions for an entry
	 */
	async countByEntry(collection: string, entryId: string): Promise<number> {
		const result = await this.db
			.selectFrom("revisions")
			.select((eb) => eb.fn.count("id").as("count"))
			.where("collection", "=", collection)
			.where("entry_id", "=", entryId)
			.executeTakeFirst();

		return Number(result?.count || 0);
	}

	/**
	 * Delete all revisions for an entry (use when entry is deleted)
	 */
	async deleteByEntry(collection: string, entryId: string): Promise<number> {
		const result = await this.db
			.deleteFrom("revisions")
			.where("collection", "=", collection)
			.where("entry_id", "=", entryId)
			.executeTakeFirst();

		return Number(result.numDeletedRows ?? 0);
	}

	/**
	 * Delete old revisions, keeping the most recent N
	 */
	async pruneOldRevisions(collection: string, entryId: string, keepCount: number): Promise<number> {
		// Get IDs of revisions to keep
		const keep = await this.db
			.selectFrom("revisions")
			.select("id")
			.where("collection", "=", collection)
			.where("entry_id", "=", entryId)
			.orderBy("created_at", "desc")
			.orderBy("id", "desc") // ULID tiebreaker
			.limit(keepCount)
			.execute();

		const keepIds = keep.map((r) => r.id);

		if (keepIds.length === 0) return 0;

		// Delete everything else for this entry
		const result = await this.db
			.deleteFrom("revisions")
			.where("collection", "=", collection)
			.where("entry_id", "=", entryId)
			.where("id", "not in", keepIds)
			.executeTakeFirst();

		return Number(result.numDeletedRows ?? 0);
	}

	/**
	 * Update revision data in place
	 * Used for autosave to avoid creating many small revisions.
	 */
	async updateData(id: string, data: Record<string, unknown>): Promise<void> {
		await this.db
			.updateTable("revisions")
			.set({ data: JSON.stringify(data) })
			.where("id", "=", id)
			.execute();
	}

	/**
	 * Convert database row to Revision object
	 */
	private rowToRevision(row: {
		id: string;
		collection: string;
		entry_id: string;
		data: string;
		author_id: string | null;
		created_at: string;
	}): Revision {
		return {
			id: row.id,
			collection: row.collection,
			entryId: row.entry_id,
			data: JSON.parse(row.data),
			authorId: row.author_id,
			createdAt: row.created_at,
		};
	}
}