package cast

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"log/slog"
	"net/http"
	"strconv"
	"time"
)

type Client struct {
	baseURL    string
	apiKey     string
	senderID   string
	httpClient *http.Client
}

func NewClient(baseURL, apiKey, senderID string) *Client {
	return &Client{
		baseURL:  baseURL,
		apiKey:   apiKey,
		senderID: senderID,
		httpClient: &http.Client{
			Timeout: 30 * time.Second,
		},
	}
}

func (c *Client) SendSMS(ctx context.Context, to, message string) (*SendResponse, error) {
	req := SendRequest{To: to, Message: message}
	if c.senderID != "" {
		req.SenderID = c.senderID
	}

	body, err := json.Marshal(req)
	if err != nil {
		return nil, err
	}

	const maxRetries = 3
	backoff := []time.Duration{1 * time.Second, 2 * time.Second, 4 * time.Second}

	for attempt := 0; attempt <= maxRetries; attempt++ {
		resp, err := c.doRequest(ctx, body)
		if err != nil {
			return nil, err
		}

		if resp.StatusCode == http.StatusTooManyRequests {
			if attempt == maxRetries {
				return nil, &CastAPIError{StatusCode: resp.StatusCode, APIError: "rate limited, max retries exceeded"}
			}
			wait := backoff[attempt]
			if ra := resp.Header.Get("Retry-After"); ra != "" {
				if secs, err := strconv.ParseFloat(ra, 64); err == nil {
					wait = time.Duration(secs * float64(time.Second))
				}
			}
			slog.Warn("cast api rate limited, retrying", "attempt", attempt+1, "wait", wait)
			resp.Body.Close()
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case <-time.After(wait):
			}
			continue
		}

		defer resp.Body.Close()
		data, err := io.ReadAll(resp.Body)
		if err != nil {
			return nil, err
		}

		if resp.StatusCode != http.StatusOK {
			var errResp SendResponse
			_ = json.Unmarshal(data, &errResp)
			return nil, &CastAPIError{StatusCode: resp.StatusCode, APIError: errResp.Error}
		}

		var result SendResponse
		if err := json.Unmarshal(data, &result); err != nil {
			return nil, err
		}
		if !result.Success {
			return nil, &CastAPIError{StatusCode: resp.StatusCode, APIError: result.Error}
		}
		return &result, nil
	}

	return nil, &CastAPIError{StatusCode: http.StatusTooManyRequests, APIError: "max retries exceeded"}
}

func (c *Client) doRequest(ctx context.Context, body []byte) (*http.Response, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/api/sms/send", bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	req.Header.Set("X-API-Key", c.apiKey)
	req.Header.Set("Content-Type", "application/json")
	return c.httpClient.Do(req)
}