package musicbrainz

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"time"

	"golang.org/x/time/rate"
)

const (
	baseURL   = "https://musicbrainz.org/ws/2"
	userAgent = "MetadataAggregator/0.1.0 (https://github.com/metadata-agregator)"
)

type client struct {
	http    *http.Client
	limiter *rate.Limiter
}

func newClient() *client {
	return &client{
		http: &http.Client{
			Timeout: 30 * time.Second,
		},
		limiter: rate.NewLimiter(rate.Every(time.Second), 1),
	}
}

func (c *client) get(ctx context.Context, endpoint string, params url.Values) ([]byte, error) {
	if err := c.limiter.Wait(ctx); err != nil {
		return nil, fmt.Errorf("rate limiter: %w", err)
	}

	if params == nil {
		params = url.Values{}
	}
	params.Set("fmt", "json")

	reqURL := fmt.Sprintf("%s/%s?%s", baseURL, endpoint, params.Encode())

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
	if err != nil {
		return nil, fmt.Errorf("create request: %w", err)
	}

	req.Header.Set("User-Agent", userAgent)
	req.Header.Set("Accept", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("do request: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusNotFound {
		return nil, ErrNotFound
	}

	if resp.StatusCode == http.StatusServiceUnavailable {
		return nil, ErrRateLimited
	}

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("unexpected status %d: %s", resp.StatusCode, string(body))
	}

	return io.ReadAll(resp.Body)
}

func (c *client) lookup(ctx context.Context, entity, id string, inc []string) ([]byte, error) {
	params := url.Values{}
	if len(inc) > 0 {
		incStr := ""
		for i, v := range inc {
			if i > 0 {
				incStr += "+"
			}
			incStr += v
		}
		params.Set("inc", incStr)
	}

	return c.get(ctx, fmt.Sprintf("%s/%s", entity, id), params)
}

func (c *client) browse(ctx context.Context, entity, linkedEntity, linkedID string, limit, offset int, inc []string) ([]byte, error) {
	params := url.Values{}
	params.Set(linkedEntity, linkedID)
	params.Set("limit", fmt.Sprintf("%d", limit))
	params.Set("offset", fmt.Sprintf("%d", offset))

	if len(inc) > 0 {
		incStr := ""
		for i, v := range inc {
			if i > 0 {
				incStr += "+"
			}
			incStr += v
		}
		params.Set("inc", incStr)
	}

	return c.get(ctx, entity, params)
}

func (c *client) search(ctx context.Context, entity, query string, limit, offset int) ([]byte, error) {
	params := url.Values{}
	params.Set("query", query)
	params.Set("limit", fmt.Sprintf("%d", limit))
	params.Set("offset", fmt.Sprintf("%d", offset))

	return c.get(ctx, entity, params)
}

func decode[T any](data []byte) (*T, error) {
	var result T
	if err := json.Unmarshal(data, &result); err != nil {
		return nil, fmt.Errorf("decode: %w", err)
	}
	return &result, nil
}