package user

import (
	"bytes"
	"fmt"
	"image"
	_ "image/jpeg"
	_ "image/png"
	"io"
	"net/http"
	"path/filepath"
	"strings"
)

const (
	MaxWidth      = 512
	MaxHeight     = 512
	MaxUploadSize = 5 * 1024 * 1024
)

func VerifyImageLimit(r io.Reader) error {
	cfg, format, err := image.DecodeConfig(r)
	if err != nil {
		return fmt.Errorf("failed to decode image: %w", err)
	}

	switch format {
	case "jpeg", "png":
		// Allowed formats
	default:
		return fmt.Errorf("not supported format: %s", format)
	}

	if cfg.Width > MaxWidth || cfg.Height > MaxHeight {
		return fmt.Errorf("image dimensions exceed limits: %dx%d (max %dx%d)", cfg.Width, cfg.Height, MaxWidth, MaxHeight)
	}

	return nil
}

func ExtractUploadedImageBytes(r *http.Request, formKey string) ([]byte, string, error) {
	// Read file with a size limit to prevent abuse. We read the raw multipart
	// bytes, verify size and image format, then return them.
	const maxRead = MaxUploadSize + 1024 // small extra for multipart framing

	file, header, err := r.FormFile(formKey)
	if err != nil {
		return nil, "", fmt.Errorf("form error: %w", err)
	}
	defer file.Close()

	ext := strings.ToLower(filepath.Ext(header.Filename))
	if ext != ".jpg" && ext != ".jpeg" && ext != ".png" {
		return nil, "", fmt.Errorf("invalid file type: only JPG or PNG are allowed")
	}

	// Read all bytes so we can verify image dimensions from a reusable reader.
	lr := io.LimitReader(file, maxRead)
	fileBytes, err := io.ReadAll(lr)
	if err != nil {
		return nil, "", err
	}
	if int64(len(fileBytes)) >= maxRead {
		return nil, "", fmt.Errorf("file too large (max %d bytes)", MaxUploadSize)
	}

	if err := VerifyImageLimit(bytes.NewReader(fileBytes)); err != nil {
		return nil, "", fmt.Errorf("invalid file: %w", err)
	}

	return fileBytes, header.Filename, nil
}