import {
  Inject,
  Injectable,
  Logger,
  Optional,
  type OnModuleDestroy,
  type OnModuleInit,
} from '@nestjs/common';
import { ModelRegistry, AuthStorage } from '@mariozechner/pi-coding-agent';
import { getModel, type Model, type Api } from '@mariozechner/pi-ai';
import type {
  CustomProviderConfig,
  IProviderAdapter,
  ModelInfo,
  ProviderHealth,
  ProviderInfo,
} from '@mosaicstack/types';
import {
  AnthropicAdapter,
  OllamaAdapter,
  OpenAIAdapter,
  OpenRouterAdapter,
  ZaiAdapter,
} from './adapters/index.js';
import type { TestConnectionResultDto } from './provider.dto.js';
import { ProviderCredentialsService } from './provider-credentials.service.js';

/** Default health check interval in seconds */
const DEFAULT_HEALTH_INTERVAL_SECS = 60;

/** DI injection token for the provider adapter array. */
export const PROVIDER_ADAPTERS = Symbol('PROVIDER_ADAPTERS');

/** Environment variable names for well-known providers */
const PROVIDER_ENV_KEYS: Record<string, string> = {
  anthropic: 'ANTHROPIC_API_KEY',
  openai: 'OPENAI_API_KEY',
  openrouter: 'OPENROUTER_API_KEY',
  zai: 'ZAI_API_KEY',
};

@Injectable()
export class ProviderService implements OnModuleInit, OnModuleDestroy {
  private readonly logger = new Logger(ProviderService.name);
  private registry!: ModelRegistry;

  constructor(
    @Optional()
    @Inject(ProviderCredentialsService)
    private readonly credentialsService: ProviderCredentialsService | null,
  ) {}

  /**
   * Adapters registered with this service.
   * Built-in adapters (Ollama) are always present; additional adapters can be
   * supplied via the PROVIDER_ADAPTERS injection token in the future.
   */
  private adapters: IProviderAdapter[] = [];

  /**
   * Cached health status per provider, updated by the health check scheduler.
   */
  private healthCache: Map<string, ProviderHealth & { modelCount: number }> = new Map();

  /** Timer handle for the periodic health check scheduler */
  private healthCheckTimer: ReturnType<typeof setInterval> | null = null;

  async onModuleInit(): Promise<void> {
    const authStorage = AuthStorage.inMemory();
    this.registry = ModelRegistry.inMemory(authStorage);

    // Build the default set of adapters that rely on the registry
    this.adapters = [
      new OllamaAdapter(this.registry),
      new AnthropicAdapter(this.registry),
      new OpenAIAdapter(this.registry),
      new OpenRouterAdapter(),
      new ZaiAdapter(),
    ];

    // Run all adapter registrations first (Ollama, Anthropic, OpenAI, OpenRouter, Z.ai)
    await this.registerAll();

    // Register API-key providers directly (custom)
    this.registerCustomProviders();

    const available = this.registry.getAvailable();
    this.logger.log(`Providers initialized: ${available.length} models available`);

    // Kick off the health check scheduler
    this.startHealthCheckScheduler();
  }

  onModuleDestroy(): void {
    if (this.healthCheckTimer !== null) {
      clearInterval(this.healthCheckTimer);
      this.healthCheckTimer = null;
    }
  }

  // ---------------------------------------------------------------------------
  // Health check scheduler
  // ---------------------------------------------------------------------------

  /**
   * Start periodic health checks on all adapters.
   * Interval is configurable via PROVIDER_HEALTH_INTERVAL env (seconds, default 60).
   */
  private startHealthCheckScheduler(): void {
    const intervalSecs =
      parseInt(process.env['PROVIDER_HEALTH_INTERVAL'] ?? '', 10) || DEFAULT_HEALTH_INTERVAL_SECS;
    const intervalMs = intervalSecs * 1000;

    // Run an initial check immediately (non-blocking)
    void this.runScheduledHealthChecks();

    this.healthCheckTimer = setInterval(() => {
      void this.runScheduledHealthChecks();
    }, intervalMs);

    this.logger.log(`Provider health check scheduler started (interval: ${intervalSecs}s)`);
  }

  private async runScheduledHealthChecks(): Promise<void> {
    for (const adapter of this.adapters) {
      try {
        const health = await adapter.healthCheck();
        const modelCount = adapter.listModels().length;
        this.healthCache.set(adapter.name, { ...health, modelCount });
        this.logger.debug(
          `Health check [${adapter.name}]: ${health.status} (${health.latencyMs ?? 'n/a'}ms)`,
        );
      } catch (err) {
        const modelCount = adapter.listModels().length;
        this.healthCache.set(adapter.name, {
          status: 'down',
          lastChecked: new Date().toISOString(),
          error: err instanceof Error ? err.message : String(err),
          modelCount,
        });
      }
    }
  }

  /**
   * Return the cached health status for all adapters.
   * Format: array of { name, status, latencyMs, lastChecked, modelCount }
   */
  getProvidersHealth(): Array<{
    name: string;
    status: string;
    latencyMs?: number;
    lastChecked: string;
    modelCount: number;
    error?: string;
  }> {
    return this.adapters.map((adapter) => {
      const cached = this.healthCache.get(adapter.name);
      if (cached) {
        return {
          name: adapter.name,
          status: cached.status,
          latencyMs: cached.latencyMs,
          lastChecked: cached.lastChecked,
          modelCount: cached.modelCount,
          error: cached.error,
        };
      }
      // Not yet checked — return a pending placeholder
      return {
        name: adapter.name,
        status: 'unknown',
        lastChecked: new Date().toISOString(),
        modelCount: adapter.listModels().length,
      };
    });
  }

  // ---------------------------------------------------------------------------
  // Adapter-pattern API
  // ---------------------------------------------------------------------------

  /**
   * Call register() on each adapter in order.
   * Errors from individual adapters are logged and do not abort the others.
   */
  async registerAll(): Promise<void> {
    for (const adapter of this.adapters) {
      try {
        await adapter.register();
      } catch (err) {
        this.logger.error(
          `Adapter "${adapter.name}" registration failed`,
          err instanceof Error ? err.stack : String(err),
        );
      }
    }
  }

  /**
   * Return the adapter registered under the given provider name, or undefined.
   */
  getAdapter(providerName: string): IProviderAdapter | undefined {
    return this.adapters.find((a) => a.name === providerName);
  }

  /**
   * Run healthCheck() on all adapters and return results keyed by provider name.
   */
  async healthCheckAll(): Promise<Record<string, ProviderHealth>> {
    const results: Record<string, ProviderHealth> = {};
    await Promise.all(
      this.adapters.map(async (adapter) => {
        try {
          results[adapter.name] = await adapter.healthCheck();
        } catch (err) {
          results[adapter.name] = {
            status: 'down',
            lastChecked: new Date().toISOString(),
            error: err instanceof Error ? err.message : String(err),
          };
        }
      }),
    );
    return results;
  }

  // ---------------------------------------------------------------------------
  // Legacy / Pi-SDK-facing API (preserved for AgentService and RoutingService)
  // ---------------------------------------------------------------------------

  getRegistry(): ModelRegistry {
    return this.registry;
  }

  findModel(provider: string, modelId: string): Model<Api> | undefined {
    return this.registry.find(provider, modelId);
  }

  getDefaultModel(): Model<Api> | undefined {
    const available = this.registry.getAvailable();
    return available[0];
  }

  listProviders(): ProviderInfo[] {
    const allModels = this.registry.getAll();
    const availableModels = this.registry.getAvailable();
    const availableIds = new Set(availableModels.map((m) => `${m.provider}:${m.id}`));

    const providerMap = new Map<string, ProviderInfo>();

    for (const model of allModels) {
      let info = providerMap.get(model.provider);
      if (!info) {
        info = {
          id: model.provider,
          name: model.provider,
          available: false,
          models: [],
        };
        providerMap.set(model.provider, info);
      }

      const isAvailable = availableIds.has(`${model.provider}:${model.id}`);
      if (isAvailable) info.available = true;

      info.models.push(this.toModelInfo(model));
    }

    return Array.from(providerMap.values());
  }

  listAvailableModels(): ModelInfo[] {
    return this.registry.getAvailable().map((m) => this.toModelInfo(m));
  }

  async testConnection(providerId: string, baseUrl?: string): Promise<TestConnectionResultDto> {
    // Delegate to the adapter when one exists and no URL override is given
    const adapter = this.getAdapter(providerId);
    if (adapter && !baseUrl) {
      const health = await adapter.healthCheck();
      return {
        providerId,
        reachable: health.status !== 'down',
        latencyMs: health.latencyMs,
        error: health.error,
      };
    }

    // Resolve baseUrl: explicit override > registered provider > ollama env
    let resolvedUrl = baseUrl;

    if (!resolvedUrl) {
      const allModels = this.registry.getAll();
      const providerModels = allModels.filter((m) => m.provider === providerId);
      if (providerModels.length === 0) {
        return { providerId, reachable: false, error: `Provider '${providerId}' not found` };
      }
      // For Ollama, derive the base URL from environment
      if (providerId === 'ollama') {
        const ollamaUrl = process.env['OLLAMA_BASE_URL'] ?? process.env['OLLAMA_HOST'];
        if (!ollamaUrl) {
          return { providerId, reachable: false, error: 'OLLAMA_BASE_URL not configured' };
        }
        resolvedUrl = `${ollamaUrl}/v1/models`;
      } else {
        // For other providers, we can only do a basic check
        return { providerId, reachable: true, discoveredModels: providerModels.map((m) => m.id) };
      }
    } else {
      resolvedUrl = resolvedUrl.replace(/\/?$/, '') + '/models';
    }

    const start = Date.now();
    try {
      const res = await fetch(resolvedUrl, {
        method: 'GET',
        headers: { Accept: 'application/json' },
        signal: AbortSignal.timeout(5000),
      });

      const latencyMs = Date.now() - start;

      if (!res.ok) {
        return { providerId, reachable: false, latencyMs, error: `HTTP ${res.status}` };
      }

      let discoveredModels: string[] | undefined;
      try {
        const json = (await res.json()) as { models?: Array<{ id?: string; name?: string }> };
        if (Array.isArray(json.models)) {
          discoveredModels = json.models.map((m) => m.id ?? m.name ?? '').filter(Boolean);
        }
      } catch {
        // ignore parse errors — endpoint was reachable
      }

      return { providerId, reachable: true, latencyMs, discoveredModels };
    } catch (err) {
      const latencyMs = Date.now() - start;
      const message = err instanceof Error ? err.message : String(err);
      return { providerId, reachable: false, latencyMs, error: message };
    }
  }

  registerCustomProvider(config: CustomProviderConfig): void {
    this.registry.registerProvider(config.id, {
      baseUrl: config.baseUrl,
      apiKey: config.apiKey,
      models: config.models.map((m) => ({
        id: m.id,
        name: m.name,
        reasoning: m.reasoning ?? false,
        input: ['text'] as ('text' | 'image')[],
        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
        contextWindow: m.contextWindow ?? 4096,
        maxTokens: m.maxTokens ?? 4096,
      })),
    });

    this.logger.log(`Registered custom provider: ${config.id} (${config.models.length} models)`);
  }

  // ---------------------------------------------------------------------------
  // Private helpers
  // ---------------------------------------------------------------------------

  private registerCustomProviders(): void {
    const customJson = process.env['MOSAIC_CUSTOM_PROVIDERS'];
    if (!customJson) return;

    try {
      const configs = JSON.parse(customJson) as CustomProviderConfig[];
      for (const config of configs) {
        this.registerCustomProvider(config);
      }
    } catch (err) {
      this.logger.error('Failed to parse MOSAIC_CUSTOM_PROVIDERS', String(err));
    }
  }

  /**
   * Resolve an API key for a provider, scoped to a specific user.
   * User-stored credentials take precedence over environment variables.
   * Returns null if no key is available from either source.
   */
  async resolveApiKey(userId: string, provider: string): Promise<string | null> {
    if (this.credentialsService) {
      const userKey = await this.credentialsService.retrieve(userId, provider);
      if (userKey) {
        this.logger.debug(`Using user-scoped credential for user=${userId} provider=${provider}`);
        return userKey;
      }
    }

    // Fall back to environment variable
    const envVar = PROVIDER_ENV_KEYS[provider];
    const envKey = envVar ? (process.env[envVar] ?? null) : null;
    if (envKey) {
      this.logger.debug(`Using env-var credential for provider=${provider}`);
    }
    return envKey;
  }

  private cloneBuiltInModel(
    provider: string,
    modelId: string,
    overrides: Partial<Model<Api>> = {},
  ): Model<Api> {
    const model = getModel(provider as never, modelId as never) as Model<Api> | undefined;
    if (!model) {
      throw new Error(`Built-in model not found: ${provider}:${modelId}`);
    }

    return { ...model, ...overrides };
  }

  private toModelInfo(model: Model<Api>): ModelInfo {
    return {
      id: model.id,
      provider: model.provider,
      name: model.name,
      reasoning: model.reasoning,
      contextWindow: model.contextWindow,
      maxTokens: model.maxTokens,
      inputTypes: model.input,
      cost: model.cost,
    };
  }
}