package blob

import (
	"context"
	"fmt"
	"io"
	"os"
	"strings"

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

// Uploader stores public avatar objects.
type Uploader interface {
	Enabled() bool
	Upload(ctx context.Context, obj FileUpload) (publicURL string, err error)
	Delete(ctx context.Context, key string) error
}

// FileUpload is a file body to store (e.g. an avatar).
type FileUpload struct {
	Key         string
	Body        io.Reader
	ContentType string
	Size        int64
}

// Disabled is a no-op uploader used when Spaces is not configured.
type Disabled struct{}

// SpacesConfig holds DigitalOcean Spaces settings.
type SpacesConfig struct {
	Key      string
	Secret   string
	Region   string
	Bucket   string
	Endpoint string // e.g. https://nyc3.digitaloceanspaces.com
	CDNBase  string // optional public base URL without trailing slash
}

type spaces struct {
	client *s3.Client
	cfg    SpacesConfig
}

func (Disabled) Enabled() bool { return false }

func (Disabled) Upload(context.Context, FileUpload) (string, error) {
	return "", fmt.Errorf("avatar uploads are not configured")
}

func (Disabled) Delete(context.Context, string) error { return nil }

// FromEnv builds an Uploader from SPACES_* environment variables.
func FromEnv() Uploader {
	return NewSpaces(SpacesConfig{
		Key:      os.Getenv("SPACES_KEY"),
		Secret:   os.Getenv("SPACES_SECRET"),
		Region:   os.Getenv("SPACES_REGION"),
		Bucket:   os.Getenv("SPACES_BUCKET"),
		Endpoint: os.Getenv("SPACES_ENDPOINT"),
		CDNBase:  os.Getenv("SPACES_CDN_BASE"),
	})
}

// NewSpaces returns an Uploader when required env is present; otherwise Disabled.
func NewSpaces(cfg SpacesConfig) Uploader {
	cfg.Key = strings.TrimSpace(cfg.Key)
	cfg.Secret = strings.TrimSpace(cfg.Secret)
	cfg.Region = strings.TrimSpace(cfg.Region)
	cfg.Bucket = strings.TrimSpace(cfg.Bucket)
	cfg.Endpoint = strings.TrimSpace(cfg.Endpoint)
	cfg.CDNBase = strings.TrimRight(strings.TrimSpace(cfg.CDNBase), "/")
	if cfg.Key == "" || cfg.Secret == "" || cfg.Region == "" || cfg.Bucket == "" || cfg.Endpoint == "" {
		return Disabled{}
	}
	client := s3.New(s3.Options{
		Region:       cfg.Region,
		Credentials:  credentials.NewStaticCredentialsProvider(cfg.Key, cfg.Secret, ""),
		BaseEndpoint: aws.String(cfg.Endpoint),
	})
	return &spaces{client: client, cfg: cfg}
}

func (s *spaces) Enabled() bool { return true }

func (s *spaces) Upload(ctx context.Context, obj FileUpload) (string, error) {
	key := strings.TrimPrefix(obj.Key, "/")
	input := &s3.PutObjectInput{
		Bucket:      aws.String(s.cfg.Bucket),
		Key:         aws.String(key),
		Body:        obj.Body,
		ContentType: aws.String(obj.ContentType),
		ACL:         types.ObjectCannedACLPublicRead,
	}
	if obj.Size > 0 {
		input.ContentLength = aws.Int64(obj.Size)
	}
	if _, err := s.client.PutObject(ctx, input); err != nil {
		return "", err
	}
	return s.publicURL(key), nil
}

func (s *spaces) Delete(ctx context.Context, key string) error {
	key = strings.TrimPrefix(key, "/")
	if key == "" {
		return nil
	}
	_, err := s.client.DeleteObject(ctx, &s3.DeleteObjectInput{
		Bucket: aws.String(s.cfg.Bucket),
		Key:    aws.String(key),
	})
	return err
}

func (s *spaces) publicURL(key string) string {
	if s.cfg.CDNBase != "" {
		return s.cfg.CDNBase + "/" + key
	}
	host := strings.TrimPrefix(s.cfg.Endpoint, "https://")
	host = strings.TrimPrefix(host, "http://")
	return fmt.Sprintf("https://%s.%s/%s", s.cfg.Bucket, host, key)
}

// KeyFromPublicURL extracts the object key from a Spaces/CDN URL when possible.
func KeyFromPublicURL(publicURL, cdnBase, bucket, endpoint string) string {
	publicURL = strings.TrimSpace(publicURL)
	if publicURL == "" {
		return ""
	}
	cdnBase = strings.TrimRight(strings.TrimSpace(cdnBase), "/")
	if cdnBase != "" && strings.HasPrefix(publicURL, cdnBase+"/") {
		return strings.TrimPrefix(publicURL, cdnBase+"/")
	}
	host := strings.TrimPrefix(strings.TrimSpace(endpoint), "https://")
	host = strings.TrimPrefix(host, "http://")
	prefix := fmt.Sprintf("https://%s.%s/", bucket, host)
	if strings.HasPrefix(publicURL, prefix) {
		return strings.TrimPrefix(publicURL, prefix)
	}
	return ""
}