// Package upload 提供受控头像文件的上传、校验与读取能力。
// 版本：v1.0.0
package upload

import (
	"bytes"
	"errors"
	"image"
	_ "image/jpeg"
	_ "image/png"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"git.apinb.com/bsm-sdk/core/errcode"
	"git.apinb.com/bsm-sdk/core/infra"
	sdkmiddleware "git.apinb.com/bsm-sdk/core/middleware"
	"git.apinb.com/heqiapp/platforms/backend/api/internal/models"
	"github.com/gin-gonic/gin"
)

const (
	maxAvatarSize      int64 = 2 << 20
	maxAvatarDimension       = 4096
)

// UploadAvatar 接收 JPG/PNG 头像，验证真实图片内容后写入受控目录。
func UploadAvatar(ctx *gin.Context) {
	ctx.Request.Body = http.MaxBytesReader(ctx.Writer, ctx.Request.Body, maxAvatarSize+(256<<10))
	fileHeader, err := ctx.FormFile("file")
	if err != nil || fileHeader == nil || fileHeader.Size <= 0 || fileHeader.Size > maxAvatarSize {
		infra.Response.Error(ctx, errcode.ErrInvalidArgument)
		return
	}

	file, err := fileHeader.Open()
	if err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	defer file.Close()

	content, err := io.ReadAll(io.LimitReader(file, maxAvatarSize+1))
	if err != nil || int64(len(content)) > maxAvatarSize {
		infra.Response.Error(ctx, errcode.ErrInvalidArgument)
		return
	}
	extension, contentType, err := validateAvatar(fileHeader.Filename, content)
	if err != nil {
		infra.Response.Error(ctx, errcode.ErrInvalidArgument)
		return
	}

	datePath := time.Now().Format("2006/01/02")
	filename := models.NewIdentity() + extension
	directory := filepath.Join(uploadRoot(), "avatars", filepath.FromSlash(datePath))
	if err := os.MkdirAll(directory, 0o750); err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	targetPath := filepath.Join(directory, filename)
	target, err := os.OpenFile(targetPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o640)
	if err != nil {
		infra.Response.Error(ctx, err)
		return
	}
	if _, err = target.Write(content); err != nil {
		target.Close()
		_ = os.Remove(targetPath)
		infra.Response.Error(ctx, err)
		return
	}
	if err = target.Close(); err != nil {
		_ = os.Remove(targetPath)
		infra.Response.Error(ctx, err)
		return
	}

	uri := "/uploads/avatars/" + datePath + "/" + filename
	infra.Response.Success(ctx, UploadFileReply{
		URI:          uri,
		OriginalName: fileHeader.Filename,
		ContentType:  contentType,
		Size:         int64(len(content)),
	})
	if claims, parseErr := sdkmiddleware.ParseAuth(ctx); parseErr == nil {
		log.Printf("avatar upload client=%s account=%s type=%s size=%d uri=%s", claims.Client, claims.Identity, contentType, len(content), uri)
	}
}

// ServeAvatar 仅从头像受控目录读取文件，拒绝外部 URL 与目录穿越路径。
func ServeAvatar(ctx *gin.Context, uri string) {
	path, err := avatarPathFromURI(uri)
	if err != nil {
		ctx.Status(http.StatusNotFound)
		return
	}
	file, err := os.Open(path)
	if err != nil {
		ctx.Status(http.StatusNotFound)
		return
	}
	defer file.Close()
	info, err := file.Stat()
	if err != nil || !info.Mode().IsRegular() {
		ctx.Status(http.StatusNotFound)
		return
	}
	ctx.Header("Cache-Control", "private, no-store")
	ctx.Header("X-Content-Type-Options", "nosniff")
	http.ServeContent(ctx.Writer, ctx.Request, filepath.Base(path), info.ModTime(), file)
}

// validateAvatar 验证扩展名、MIME、尺寸和完整解码结果，返回规范化扩展名。
func validateAvatar(filename string, content []byte) (string, string, error) {
	extension := strings.ToLower(filepath.Ext(filename))
	if extension != ".jpg" && extension != ".jpeg" && extension != ".png" {
		return "", "", errors.New("unsupported avatar extension")
	}
	contentType := http.DetectContentType(content)
	expectedType := "image/jpeg"
	normalizedExtension := ".jpg"
	if extension == ".png" {
		expectedType = "image/png"
		normalizedExtension = ".png"
	}
	if contentType != expectedType {
		return "", "", errors.New("avatar content type mismatch")
	}
	config, format, err := image.DecodeConfig(bytes.NewReader(content))
	if err != nil || config.Width <= 0 || config.Height <= 0 ||
		config.Width > maxAvatarDimension || config.Height > maxAvatarDimension {
		return "", "", errors.New("invalid avatar dimensions")
	}
	if (expectedType == "image/jpeg" && format != "jpeg") || (expectedType == "image/png" && format != "png") {
		return "", "", errors.New("avatar format mismatch")
	}
	if _, _, err := image.Decode(bytes.NewReader(content)); err != nil {
		return "", "", errors.New("invalid avatar content")
	}
	return normalizedExtension, expectedType, nil
}

// avatarPathFromURI 将数据库中的受控 URI 映射为头像目录内的真实文件路径。
func avatarPathFromURI(uri string) (string, error) {
	const prefix = "/uploads/avatars/"
	if !strings.HasPrefix(uri, prefix) {
		return "", errors.New("avatar URI is not controlled")
	}
	root, err := filepath.Abs(filepath.Join(uploadRoot(), "avatars"))
	if err != nil {
		return "", err
	}
	relative := filepath.Clean(filepath.FromSlash(strings.TrimPrefix(uri, "/uploads/avatars/")))
	if relative == "." || filepath.IsAbs(relative) || relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
		return "", errors.New("invalid avatar path")
	}
	candidate, err := filepath.Abs(filepath.Join(root, relative))
	if err != nil {
		return "", err
	}
	relativeToRoot, err := filepath.Rel(root, candidate)
	if err != nil || relativeToRoot == ".." || strings.HasPrefix(relativeToRoot, ".."+string(filepath.Separator)) {
		return "", errors.New("avatar path escapes root")
	}
	return candidate, nil
}