import type Database from 'better-sqlite3';
import type { EmbeddingSettingsUpdateDto } from '$lib/dtos/embedding-settings.js';
import {
	createProviderFromProfile,
	getDefaultLocalProfile
} from '$lib/server/embeddings/registry.js';
import { EmbeddingProfileMapper } from '$lib/server/mappers/embedding-profile.mapper.js';
import { EmbeddingProfile, EmbeddingProfileEntity } from '$lib/server/models/embedding-profile.js';
import { EmbeddingSettings } from '$lib/server/models/embedding-settings.js';
import { InvalidInputError } from '$lib/server/utils/validation.js';

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

	getSettings(): EmbeddingSettings {
		const profiles = this.loadProfiles();
		const activeProfile = profiles.find((profile) => profile.isDefault && profile.enabled) ?? null;

		return new EmbeddingSettings({ profiles, activeProfile });
	}

	async updateSettings(input: EmbeddingSettingsUpdateDto): Promise<EmbeddingSettings> {
		const now = Math.floor(Date.now() / 1000);

		this.db.prepare('UPDATE embedding_profiles SET is_default = 0, updated_at = ?').run(now);

		if (input.activeProfileId === null) {
			return this.getSettings();
		}

		const profile =
			input.activeProfileId === 'local-default'
				? this.buildDefaultLocalProfile(now)
				: this.buildCustomProfile(input, now);

		const available = await createProviderFromProfile(profile).isAvailable();
		if (!available) {
			throw new InvalidInputError(
				`Could not connect to the "${profile.providerKind}" provider. Check your configuration.`
			);
		}

		this.persistProfile(profile);
		return this.getSettings();
	}

	private loadProfiles(): EmbeddingProfile[] {
		return this.db
			.prepare('SELECT * FROM embedding_profiles ORDER BY is_default DESC, created_at ASC')
			.all()
			.map((row) => EmbeddingProfileMapper.fromEntity(new EmbeddingProfileEntity(row as never)));
	}

	private buildDefaultLocalProfile(now: number): EmbeddingProfile {
		const defaultLocal = getDefaultLocalProfile();

		return new EmbeddingProfile({
			id: defaultLocal.id,
			providerKind: defaultLocal.providerKind,
			title: defaultLocal.title,
			enabled: true,
			isDefault: true,
			model: defaultLocal.model,
			dimensions: defaultLocal.dimensions,
			config: {},
			createdAt: this.getCreatedAt(defaultLocal.id, now),
			updatedAt: now
		});
	}

	private buildCustomProfile(input: EmbeddingSettingsUpdateDto, now: number): EmbeddingProfile {
		const candidate = input.profile;
		if (!candidate) {
			throw new InvalidInputError('profile is required for custom embedding providers');
		}
		if (candidate.id !== input.activeProfileId) {
			throw new InvalidInputError('activeProfileId must match profile.id');
		}
		if (!candidate.title || !candidate.model) {
			throw new InvalidInputError('profile title and model are required');
		}

		return new EmbeddingProfile({
			id: candidate.id,
			providerKind: candidate.providerKind,
			title: candidate.title,
			enabled: true,
			isDefault: true,
			model: candidate.model,
			dimensions: candidate.dimensions,
			config: candidate.config,
			createdAt: this.getCreatedAt(candidate.id, now),
			updatedAt: now
		});
	}

	private getCreatedAt(id: string, fallback: number): number {
		return (
			this.db
				.prepare<
					[string],
					{ created_at: number }
				>('SELECT created_at FROM embedding_profiles WHERE id = ?')
				.get(id)?.created_at ?? fallback
		);
	}

	private persistProfile(profile: EmbeddingProfile): void {
		this.db
			.prepare(
				`INSERT INTO embedding_profiles
				   (id, provider_kind, title, enabled, is_default, model, dimensions, config, created_at, updated_at)
				 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
				 ON CONFLICT(id) DO UPDATE SET
				   provider_kind = excluded.provider_kind,
				   title = excluded.title,
				   enabled = excluded.enabled,
				   is_default = excluded.is_default,
				   model = excluded.model,
				   dimensions = excluded.dimensions,
				   config = excluded.config,
				   updated_at = excluded.updated_at`
			)
			.run(
				profile.id,
				profile.providerKind,
				profile.title,
				profile.enabled ? 1 : 0,
				profile.isDefault ? 1 : 0,
				profile.model,
				profile.dimensions,
				JSON.stringify(profile.config),
				profile.createdAt,
				profile.updatedAt
			);
	}
}