import type { BikeRoute, BikeStep } from "@timetoleave/core";
import { OSRM_URL } from "./constants";
import { ApiClient } from "./api-service";

// ---------------------------------------------------------------------------
// OSRM response types (internal, not exported)
// ---------------------------------------------------------------------------

interface OsrmStep {
  name: string;
  distance: number;
  duration: number;
  maneuver: { instruction?: string; type: string; modifier?: string };
}

interface OsrmRoute {
  distance: number;
  duration: number;
  legs: Array<{ steps: OsrmStep[] }>;
}

interface OsrmResponse {
  code: string;
  routes: OsrmRoute[];
}

// ---------------------------------------------------------------------------
// Helper: Build human-readable instruction from OSRM step data
// ---------------------------------------------------------------------------

function stepInstruction(step: OsrmStep): string {
  if (step.maneuver.instruction) return step.maneuver.instruction;
  const modifier = step.maneuver.modifier ? ` ${step.maneuver.modifier}` : "";
  return `${step.maneuver.type}${modifier}${step.name ? ` onto ${step.name}` : ""}`;
}

// ---------------------------------------------------------------------------
// WalkRoutingClient — Wraps the OSRM foot routing API
//
// OSRM routes are cached for 5 minutes. Walk routes between the same
// coordinates rarely change, and caching significantly reduces API load.
// ---------------------------------------------------------------------------

export class WalkRoutingClient {
  private client: ApiClient;
  private readonly defaultTtlMs: number;

  constructor(
    baseUrl: string = OSRM_URL,
    ttlMs: number = 5 * 60 * 1000, // 5 minutes — routes are very stable
  ) {
    this.client = new ApiClient({
      baseUrl,
      defaultTimeoutMs: 10_000,
      defaultTtlMs: ttlMs,
      maxRetries: 3,
    });
    this.defaultTtlMs = ttlMs;
  }

  async getWalkRoute(fromLat: number, fromLng: number, toLat: number, toLng: number): Promise<BikeRoute | null> {
    const coords = `${fromLng},${fromLat};${toLng},${toLat}`;
    const path = `/route/v1/foot/${coords}`;

    const cacheKey = `osrm:walk:${coords}`;

    const res = await this.client.get<OsrmResponse>(
      path,
      { overview: "false", steps: "true" },
      {
        cacheKey,
        ttl: this.defaultTtlMs,
      },
    );

    if (res.code !== "Ok" || !res.routes.length) return null;

    const route = res.routes[0];
    const steps: BikeStep[] = (route.legs[0]?.steps ?? []).map((s) => ({
      name: s.name,
      distance: s.distance,
      duration: s.duration,
      instruction: stepInstruction(s),
    }));

    return {
      distance: route.distance,
      duration: route.duration,
      steps,
    };
  }

  /**
   * Expose cache statistics for debugging/monitoring.
   */
  public cacheStats() {
    return this.client.cacheStats();
  }

  /**
   * Clear the cache (useful for testing or forced refresh).
   */
  public clearCache() {
    this.client.clearCache();
  }
}