package imgur

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"os"
	"time"
)

const uploadURL = "https://api.imgur.com/3/image"

// Client uploads images to Imgur anonymously with a Client-ID.
type Client struct {
	clientID   string
	httpClient *http.Client
}

// New creates an Imgur client. clientID may be empty (uploads will fail clearly).
func New(clientID string) *Client {
	return &Client{
		clientID: clientID,
		httpClient: &http.Client{
			Timeout: 60 * time.Second,
		},
	}
}

// Enabled reports whether a Client-ID is configured.
func (c *Client) Enabled() bool {
	return c != nil && c.clientID != ""
}

type uploadResponse struct {
	Success bool `json:"success"`
	Data    struct {
		Link string `json:"link"`
		ID   string `json:"id"`
	} `json:"data"`
	Status int `json:"status"`
}

// UploadFile uploads a local image file and returns the public Imgur URL.
func (c *Client) UploadFile(path string) (string, error) {
	if !c.Enabled() {
		return "", fmt.Errorf("imgur is not configured (set IMGUR_CLIENT_ID)")
	}

	file, err := os.Open(path)
	if err != nil {
		return "", fmt.Errorf("open screenshot: %w", err)
	}
	defer file.Close()

	var body bytes.Buffer
	writer := multipart.NewWriter(&body)
	part, err := writer.CreateFormFile("image", "screenshot.png")
	if err != nil {
		return "", err
	}
	if _, err := io.Copy(part, file); err != nil {
		return "", err
	}
	_ = writer.WriteField("type", "file")
	if err := writer.Close(); err != nil {
		return "", err
	}

	req, err := http.NewRequest(http.MethodPost, uploadURL, &body)
	if err != nil {
		return "", err
	}
	req.Header.Set("Authorization", "Client-ID "+c.clientID)
	req.Header.Set("Content-Type", writer.FormDataContentType())

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

	raw, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", err
	}

	var parsed uploadResponse
	if err := json.Unmarshal(raw, &parsed); err != nil {
		return "", fmt.Errorf("decode imgur response: %w (body=%s)", err, truncate(string(raw), 200))
	}
	if !parsed.Success || parsed.Data.Link == "" {
		return "", fmt.Errorf("imgur upload failed (status=%d): %s", resp.StatusCode, truncate(string(raw), 300))
	}
	return parsed.Data.Link, nil
}

func truncate(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n] + "..."
}