/**
 * VersionService — CRUD operations for repository_versions.
 *
 * Operates directly on the raw better-sqlite3 client for synchronous queries,
 * matching the pattern used by RepositoryService.
 */

import type Database from 'better-sqlite3';
import { RepositoryVersionMapper } from '$lib/server/mappers/repository-version.mapper.js';
import {
	RepositoryVersion,
	RepositoryVersionEntity
} from '$lib/server/models/repository-version.js';
import { AlreadyExistsError, NotFoundError } from '$lib/server/utils/validation';
import { resolveTagToCommit, discoverVersionTags } from '$lib/server/utils/git.js';

export class VersionService {
	constructor(private readonly db: Database.Database) {}

	/**
	 * List all versions for a repository, newest first.
	 */
	list(repositoryId: string): RepositoryVersion[] {
		const rows = this.db
			.prepare(
				`SELECT * FROM repository_versions
         WHERE repository_id = ?
         ORDER BY created_at DESC`
			)
			.all(repositoryId) as RepositoryVersionEntity[];
		return rows.map((row) => RepositoryVersionMapper.fromEntity(new RepositoryVersionEntity(row)));
	}

	/**
	 * Add a new version record for a repository.
	 * The version ID follows the convention: {repositoryId}/{tag}
	 *
	 * @param commitHash  Optional commit hash. If not provided and repository is local,
	 *                    will attempt to resolve the tag to a commit hash automatically.
	 *
	 * @throws NotFoundError      when the parent repository does not exist
	 * @throws AlreadyExistsError when the tag is already registered
	 */
	add(repositoryId: string, tag: string, title?: string, commitHash?: string): RepositoryVersion {
		// Verify parent repository exists.
		const repo = this.db
			.prepare(`SELECT id, source, source_url FROM repositories WHERE id = ?`)
			.get(repositoryId) as { id: string; source: string; source_url: string } | undefined;

		if (!repo) {
			throw new NotFoundError(`Repository ${repositoryId} not found`);
		}

		const id = `${repositoryId}/${tag}`;

		// Check for collision.
		const existing = this.getByTag(repositoryId, tag);
		if (existing) {
			throw new AlreadyExistsError(`Version ${tag} already exists for repository ${repositoryId}`);
		}

		// For local repositories, attempt to resolve tag to commit hash if not provided
		let resolvedCommitHash = commitHash;
		if (!resolvedCommitHash && repo.source === 'local') {
			try {
				resolvedCommitHash = resolveTagToCommit({ repoPath: repo.source_url, tag });
			} catch (error) {
				console.warn(
					`[VersionService] Could not resolve tag '${tag}' to commit hash for ${repositoryId}: ${error instanceof Error ? error.message : String(error)}`
				);
				// Continue without commit hash — non-blocking
			}
		}

		const now = Math.floor(Date.now() / 1000);

		this.db
			.prepare(
				`INSERT INTO repository_versions
         (id, repository_id, tag, title, commit_hash, state, total_snippets, indexed_at, created_at)
         VALUES (?, ?, ?, ?, ?, 'pending', 0, NULL, ?)`
			)
			.run(id, repositoryId, tag, title ?? null, resolvedCommitHash ?? null, now);

		const row = this.db
			.prepare(`SELECT * FROM repository_versions WHERE id = ?`)
			.get(id) as RepositoryVersionEntity;
		return RepositoryVersionMapper.fromEntity(new RepositoryVersionEntity(row));
	}

	/**
	 * Delete a version and all associated documents / snippets (cascades via FK).
	 *
	 * @throws NotFoundError when the version does not exist
	 */
	remove(repositoryId: string, tag: string): void {
		const version = this.getByTag(repositoryId, tag);
		if (!version) {
			throw new NotFoundError(`Version ${tag} not found for repository ${repositoryId}`);
		}

		this.db
			.prepare(`DELETE FROM repository_versions WHERE repository_id = ? AND tag = ?`)
			.run(repositoryId, tag);
	}

	/**
	 * Get a single version by tag.
	 * Returns `null` when not found.
	 */
	getByTag(repositoryId: string, tag: string): RepositoryVersion | null {
		const row = this.db
			.prepare(`SELECT * FROM repository_versions WHERE repository_id = ? AND tag = ?`)
			.get(repositoryId, tag) as RepositoryVersionEntity | undefined;
		return row ? RepositoryVersionMapper.fromEntity(new RepositoryVersionEntity(row)) : null;
	}

	/**
	 * Register multiple versions from a trueref.json `previousVersions` array.
	 * Silently skips tags that are already registered (idempotent).
	 * All new records are created with state = 'pending'.
	 *
	 * Supports optional `commitHash` field to pin a version to a specific commit,
	 * overriding tag resolution (TRUEREF-0019).
	 *
	 * @throws NotFoundError when the parent repository does not exist
	 */
	registerFromConfig(
		repositoryId: string,
		previousVersions: { tag: string; title: string; commitHash?: string }[]
	): RepositoryVersion[] {
		// Verify parent repository exists.
		const repo = this.db.prepare(`SELECT id FROM repositories WHERE id = ?`).get(repositoryId) as
			| { id: string }
			| undefined;

		if (!repo) {
			throw new NotFoundError(`Repository ${repositoryId} not found`);
		}

		const registered: RepositoryVersion[] = [];

		for (const { tag, title, commitHash } of previousVersions) {
			const existing = this.getByTag(repositoryId, tag);
			if (existing) {
				// Already registered — skip silently.
				registered.push(existing);
				continue;
			}

			const version = this.add(repositoryId, tag, title, commitHash);
			registered.push(version);
		}

		return registered;
	}

	/**
	 * Discover all version tags from a local repository and return them
	 * along with their resolved commit hashes.
	 *
	 * This is used for tag auto-discovery when adding a repository or
	 * refreshing available versions (TRUEREF-0019).
	 *
	 * @returns Array of { tag, commitHash } objects, newest first
	 * @throws Error when repository is not local or git operations fail
	 */
	discoverTags(repositoryId: string): Array<{ tag: string; commitHash: string }> {
		const repo = this.db
			.prepare(`SELECT id, source, source_url FROM repositories WHERE id = ?`)
			.get(repositoryId) as { id: string; source: string; source_url: string } | undefined;

		if (!repo) {
			throw new NotFoundError(`Repository ${repositoryId} not found`);
		}

		if (repo.source !== 'local') {
			throw new Error('Tag discovery is only supported for local repositories');
		}

		const tags = discoverVersionTags({ repoPath: repo.source_url });

		return tags.map((tag: string) => {
			const commitHash = resolveTagToCommit({ repoPath: repo.source_url, tag });
			return { tag, commitHash };
		});
	}
}