/*
Copyright 2025 linux.do
Modified by Arctel.net, 2026

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package storage

import (
	"context"
	"fmt"
	"io"
	"log"
	"net/http"
	"strings"

	"github.com/Rain-kl/Wavelet/internal/config"
	"github.com/Rain-kl/Wavelet/internal/otel_trace"
	"github.com/Rain-kl/Wavelet/internal/util"
	"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"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
	"go.opentelemetry.io/otel/trace"
)

var (
	client    *s3.Client
	bucket    string
	keyPrefix string
	cdnURL    string
)

func init() {
	cfg := config.Config.S3
	if !cfg.Enabled {
		log.Println("[Storage] S3 storage disabled")
		return
	}

	bucket = cfg.Bucket
	keyPrefix = cfg.KeyPrefix
	cdnURL = strings.TrimRight(cfg.CdnURL, "/")

	awsCfg, err := awsconfig.LoadDefaultConfig(context.Background(),
		awsconfig.WithRegion(cfg.Region),
		awsconfig.WithCredentialsProvider(
			credentials.NewStaticCredentialsProvider(cfg.AccessKeyID, cfg.SecretAccessKey, ""),
		),
	)
	if err != nil {
		log.Fatalf("[Storage] failed to load AWS config: %v\n", err)
	}

	client = s3.NewFromConfig(awsCfg, func(o *s3.Options) {
		if cfg.Endpoint != "" {
			o.BaseEndpoint = aws.String(cfg.Endpoint)
		}
		o.UsePathStyle = cfg.PathStyle
	})

	log.Printf("[Storage] S3 storage initialized (bucket: %s, prefix: %s, cdn: %s)\n", bucket, keyPrefix, cdnURL)
}

var IsEnabledFunc = func() bool {
	return client != nil
}

func IsEnabled() bool {
	return IsEnabledFunc()
}

// BuildKey constructs a full S3 object key with the configured prefix.
func BuildKey(path string) string {
	return keyPrefix + path
}

var (
	// PutObjectFunc enables mocking S3 uploads in tests.
	PutObjectFunc = putObjectDefault
	// GetObjectFunc enables mocking S3 downloads in tests.
	GetObjectFunc = getObjectDefault
	// DeleteObjectFunc enables mocking S3 deletion in tests.
	DeleteObjectFunc = deleteObjectDefault
)

// MockStorage is a test helper to mock S3 storage operations.
// It returns a function that restores original implementations.
func MockStorage(
	mockPut func(ctx context.Context, key string, body io.Reader, size int64, contentType string) error,
	mockGet func(ctx context.Context, key string) (*ObjectInfo, error),
	mockDelete func(ctx context.Context, key string) error,
) func() {
	origPut, origGet, origDelete := PutObjectFunc, GetObjectFunc, DeleteObjectFunc
	PutObjectFunc = mockPut
	GetObjectFunc = mockGet
	DeleteObjectFunc = mockDelete
	return func() {
		PutObjectFunc = origPut
		GetObjectFunc = origGet
		DeleteObjectFunc = origDelete
	}
}

// PutObject uploads a file to S3.
func PutObject(ctx context.Context, key string, body io.Reader, size int64, contentType string) error {
	return PutObjectFunc(ctx, key, body, size, contentType)
}

func putObjectDefault(ctx context.Context, key string, body io.Reader, size int64, contentType string) error {
	ctx, span := otel_trace.Start(ctx, "S3.PutObject", trace.WithSpanKind(trace.SpanKindClient))
	defer span.End()

	span.SetAttributes(
		attribute.String("s3.key", key),
		attribute.Int64("s3.content_length", size),
		attribute.String("s3.content_type", contentType),
	)

	if !IsEnabled() {
		span.SetStatus(codes.Error, "S3 not initialized")
		return ErrS3InitializationFailed{}
	}

	input := &s3.PutObjectInput{
		Bucket:        aws.String(bucket),
		Key:           aws.String(key),
		Body:          body,
		ContentLength: aws.Int64(size),
		ContentType:   aws.String(contentType),
	}

	_, err := client.PutObject(ctx, input)
	if err != nil {
		span.SetStatus(codes.Error, fmt.Sprintf("S3 put object failed: %v", err))
		return fmt.Errorf(errS3PutObjectFailed, err)
	}
	return nil
}

// ObjectInfo holds metadata about a retrieved object.
type ObjectInfo struct {
	CachePath     string
	Body          io.ReadCloser
	ContentLength int64
	ContentType   string
}

// GetObject retrieves a file directly from S3.
func GetObject(ctx context.Context, key string) (*ObjectInfo, error) {
	return GetObjectFunc(ctx, key)
}

func getObjectDefault(ctx context.Context, key string) (*ObjectInfo, error) {
	ctx, span := otel_trace.Start(ctx, "S3.GetObject", trace.WithSpanKind(trace.SpanKindClient))
	defer span.End()

	span.SetAttributes(attribute.String("s3.key", key))

	if !IsEnabled() {
		span.SetStatus(codes.Error, "S3 not initialized")
		return nil, ErrS3InitializationFailed{}
	}

	output, err := client.GetObject(ctx, &s3.GetObjectInput{
		Bucket: aws.String(bucket),
		Key:    aws.String(key),
	})
	if err != nil {
		span.SetStatus(codes.Error, fmt.Sprintf("S3 get object failed: %v", err))
		return nil, fmt.Errorf(errS3GetObjectFailed, err)
	}

	contentType := "application/octet-stream"
	if output.ContentType != nil {
		contentType = *output.ContentType
	}

	var contentLength int64
	if output.ContentLength != nil {
		contentLength = *output.ContentLength
	}

	return &ObjectInfo{
		Body:          output.Body,
		ContentLength: contentLength,
		ContentType:   contentType,
	}, nil
}

// GetObjectViaProxy retrieves a file via CDN if configured, otherwise falls back to S3.
func GetObjectViaProxy(ctx context.Context, key string) (*ObjectInfo, error) {
	ctx, span := otel_trace.Start(ctx, "S3.GetObjectViaProxy", trace.WithSpanKind(trace.SpanKindClient))
	defer span.End()

	span.SetAttributes(attribute.String("s3.key", key))

	if !IsEnabled() {
		span.SetStatus(codes.Error, "S3 not initialized")
		return nil, ErrS3InitializationFailed{}
	}

	if cdnURL == "" {
		return GetObject(ctx, key)
	}

	url := cdnURL + "/" + key
	span.SetAttributes(attribute.Bool("s3.use_cdn", true))

	resp, err := util.Request(ctx, http.MethodGet, url, nil, nil, nil)
	if err != nil {
		span.SetStatus(codes.Error, fmt.Sprintf("cdn request failed: %v", err))
		return nil, fmt.Errorf(errCDNRequestFailed, err)
	}

	if resp.StatusCode != http.StatusOK {
		resp.Body.Close()
		span.SetStatus(codes.Error, fmt.Sprintf("cdn returned status %d", resp.StatusCode))
		return nil, fmt.Errorf(errCDNStatusFailed, resp.StatusCode)
	}

	contentType := resp.Header.Get("Content-Type")
	if contentType == "" {
		contentType = "application/octet-stream"
	}

	return &ObjectInfo{
		Body:          resp.Body,
		ContentLength: resp.ContentLength,
		ContentType:   contentType,
	}, nil
}

// DeleteObject deletes a file from S3.
func DeleteObject(ctx context.Context, key string) error {
	return DeleteObjectFunc(ctx, key)
}

func deleteObjectDefault(ctx context.Context, key string) error {
	ctx, span := otel_trace.Start(ctx, "S3.DeleteObject", trace.WithSpanKind(trace.SpanKindClient))
	defer span.End()

	span.SetAttributes(attribute.String("s3.key", key))

	if !IsEnabled() {
		return ErrS3InitializationFailed{}
	}

	_, err := client.DeleteObject(ctx, &s3.DeleteObjectInput{
		Bucket: aws.String(bucket),
		Key:    aws.String(key),
	})
	if err != nil {
		span.SetStatus(codes.Error, fmt.Sprintf("S3 delete object failed: %v", err))
		return fmt.Errorf(errS3DeleteObjectFailed, err)
	}
	return nil
}