package storage

import (
	"context"
	"fmt"
	"io"
	"mime"
	"net/url"
	"path"
	"strings"

	"haixun-backend/internal/config"

	"github.com/aws/aws-sdk-go-v2/aws"
	awsconfig "github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/credentials"
	"github.com/aws/aws-sdk-go-v2/service/s3"
)

type Uploader interface {
	Upload(ctx context.Context, key, contentType string, body io.Reader) (string, error)
}

// PublicURLResolver turns stored object keys into externally reachable URLs (Threads image publish).
type PublicURLResolver interface {
	ResolvePublicURL(key string) (string, error)
}

// ObjectDeleter removes stored objects by key.
type ObjectDeleter interface {
	DeleteObject(ctx context.Context, key string) error
}

// ObjectReader fetches stored objects by key.
type ObjectReader interface {
	GetObject(ctx context.Context, key string) (io.ReadCloser, string, error)
}

// PublishAttachmentStore resolves public URLs and deletes ephemeral publish attachments.
type PublishAttachmentStore interface {
	PublicURLResolver
	ObjectDeleter
}

type S3Uploader struct {
	client        *s3.Client
	bucket        string
	publicBaseURL string
	bucketReady   bool
}

func NewS3Uploader(ctx context.Context, cfg config.S3Conf) (*S3Uploader, error) {
	if strings.TrimSpace(cfg.Bucket) == "" {
		return nil, nil
	}
	awsCfg, err := awsconfig.LoadDefaultConfig(ctx,
		awsconfig.WithRegion(cfg.Region),
		awsconfig.WithCredentialsProvider(credentials.NewStaticCredentialsProvider(cfg.AccessKey, cfg.SecretKey, "")),
	)
	if err != nil {
		return nil, err
	}
	client := s3.NewFromConfig(awsCfg, func(o *s3.Options) {
		if cfg.Endpoint != "" {
			o.BaseEndpoint = aws.String(cfg.Endpoint)
		}
		o.UsePathStyle = cfg.UsePathStyle
	})
	return &S3Uploader{client: client, bucket: cfg.Bucket, publicBaseURL: strings.TrimRight(cfg.PublicBaseURL, "/")}, nil
}

func (u *S3Uploader) Upload(ctx context.Context, key, contentType string, body io.Reader) (string, error) {
	if u == nil || u.client == nil {
		return "", fmt.Errorf("s3 uploader is not configured")
	}
	if !u.bucketReady {
		if _, err := u.client.HeadBucket(ctx, &s3.HeadBucketInput{Bucket: aws.String(u.bucket)}); err != nil {
			if _, createErr := u.client.CreateBucket(ctx, &s3.CreateBucketInput{Bucket: aws.String(u.bucket)}); createErr != nil {
				return "", createErr
			}
		}
		policy := fmt.Sprintf(`{"Version":"2012-10-17","Statement":[{"Effect":"Allow","Principal":{"AWS":["*"]},"Action":["s3:GetObject"],"Resource":["arn:aws:s3:::%s/*"]}]}`, u.bucket)
		_, _ = u.client.PutBucketPolicy(ctx, &s3.PutBucketPolicyInput{Bucket: aws.String(u.bucket), Policy: aws.String(policy)})
		u.bucketReady = true
	}
	key = strings.TrimLeft(path.Clean("/"+key), "/")
	if contentType == "" {
		contentType = mime.TypeByExtension(path.Ext(key))
	}
	if contentType == "" {
		contentType = "application/octet-stream"
	}
	_, err := u.client.PutObject(ctx, &s3.PutObjectInput{
		Bucket:      aws.String(u.bucket),
		Key:         aws.String(key),
		Body:        body,
		ContentType: aws.String(contentType),
	})
	if err != nil {
		return "", err
	}
	return key, nil
}

func (u *S3Uploader) ResolvePublicURL(key string) (string, error) {
	if u == nil {
		return "", fmt.Errorf("s3 uploader is not configured")
	}
	key = strings.TrimSpace(key)
	if key == "" {
		return "", fmt.Errorf("asset key is required")
	}
	key = NormalizeObjectKey(u.bucket, key)
	base := strings.TrimRight(strings.TrimSpace(u.publicBaseURL), "/")
	if base == "" {
		return "", fmt.Errorf("HAIXUN_STORAGE_S3_PUBLIC_BASE_URL is required for Threads image publish")
	}
	if strings.HasSuffix(base, "/public/assets") {
		return base + "?key=" + url.QueryEscape(key), nil
	}
	if strings.HasSuffix(base, "/"+u.bucket) {
		return base + "/" + key, nil
	}
	return base + "/" + key, nil
}

func (u *S3Uploader) GetObject(ctx context.Context, key string) (io.ReadCloser, string, error) {
	if u == nil || u.client == nil {
		return nil, "", fmt.Errorf("s3 uploader is not configured")
	}
	key = strings.TrimSpace(key)
	if key == "" {
		return nil, "", fmt.Errorf("asset key is required")
	}
	if !IsPublicAssetKey(key) {
		return nil, "", fmt.Errorf("asset key is not public")
	}
	key = NormalizeObjectKey(u.bucket, key)
	out, err := u.client.GetObject(ctx, &s3.GetObjectInput{
		Bucket: aws.String(u.bucket),
		Key:    aws.String(key),
	})
	if err != nil {
		return nil, "", err
	}
	contentType := ""
	if out.ContentType != nil {
		contentType = strings.TrimSpace(*out.ContentType)
	}
	if contentType == "" {
		contentType = mime.TypeByExtension(path.Ext(key))
	}
	if contentType == "" {
		contentType = "application/octet-stream"
	}
	return out.Body, contentType, nil
}

func (u *S3Uploader) DeleteObject(ctx context.Context, key string) error {
	if u == nil || u.client == nil {
		return fmt.Errorf("s3 uploader is not configured")
	}
	key = strings.TrimSpace(key)
	if key == "" {
		return nil
	}
	key = NormalizeObjectKey(u.bucket, key)
	_, err := u.client.DeleteObject(ctx, &s3.DeleteObjectInput{
		Bucket: aws.String(u.bucket),
		Key:    aws.String(key),
	})
	return err
}