package s3

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"strings"
	"sync"
	"time"

	"github.com/aws/aws-sdk-go-v2/aws"
	awss3 "github.com/aws/aws-sdk-go-v2/service/s3"
	s3types "github.com/aws/aws-sdk-go-v2/service/s3/types"
	"github.com/google/uuid"
)

// MockS3Client implements S3Client for testing without real S3 credentials.
// It generates fake presigned URLs that point to a test server.
type MockS3Client struct {
	// TestServerURL is the base URL for generating fake presigned URLs.
	// Requests to these URLs should be handled by a test server (httptest.Server).
	TestServerURL string

	// UploadID is returned by CreateMultipartUpload.
	// If empty, a UUID is generated.
	UploadID string

	// Objects stores in-memory blobs for PutObject/HeadObject/DeleteObject/CopyObject/ListObjectsV2.
	Objects map[string][]byte

	// Track calls for verification in tests
	mu                   sync.Mutex
	CreateMultipartCalls []CreateMultipartCall
	CompleteCalls        []CompleteCall
	AbortCalls           []AbortCall
	UploadPartCalls      []UploadPartCall
	GetObjectCalls       []GetObjectCall
	HeadObjectCalls      []HeadObjectCall
	PutObjectCalls       []PutObjectCall

	// Error injection for testing error handling
	CreateMultipartError error
	CompleteError        error
	AbortError           error
	HeadObjectError      error
	CopyObjectError      error
}

// CreateMultipartCall records a CreateMultipartUpload call
type CreateMultipartCall struct {
	Bucket string
	Key    string
}

// CompleteCall records a CompleteMultipartUpload call
type CompleteCall struct {
	Bucket   string
	Key      string
	UploadID string
	Parts    int
}

// AbortCall records an AbortMultipartUpload call
type AbortCall struct {
	Bucket   string
	Key      string
	UploadID string
}

// UploadPartCall records a PresignUploadPart call
type UploadPartCall struct {
	Bucket     string
	Key        string
	UploadID   string
	PartNumber int32
}

// GetObjectCall records a PresignGetObject call
type GetObjectCall struct {
	Bucket string
	Key    string
}

// HeadObjectCall records a PresignHeadObject call
type HeadObjectCall struct {
	Bucket string
	Key    string
}

// PutObjectCall records a PresignPutObject call
type PutObjectCall struct {
	Bucket string
	Key    string
}

// NewMockS3Client creates a new mock S3 client for testing
func NewMockS3Client(testServerURL string) *MockS3Client {
	return &MockS3Client{
		TestServerURL:        testServerURL,
		Objects:              make(map[string][]byte),
		CreateMultipartCalls: []CreateMultipartCall{},
		CompleteCalls:        []CompleteCall{},
		AbortCalls:           []AbortCall{},
		UploadPartCalls:      []UploadPartCall{},
		GetObjectCalls:       []GetObjectCall{},
		HeadObjectCalls:      []HeadObjectCall{},
		PutObjectCalls:       []PutObjectCall{},
	}
}

// CreateMultipartUpload implements S3Client
func (m *MockS3Client) CreateMultipartUpload(ctx context.Context, input *awss3.CreateMultipartUploadInput, opts ...func(*awss3.Options)) (*awss3.CreateMultipartUploadOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.CreateMultipartCalls = append(m.CreateMultipartCalls, CreateMultipartCall{
		Bucket: aws.ToString(input.Bucket),
		Key:    aws.ToString(input.Key),
	})

	if m.CreateMultipartError != nil {
		return nil, m.CreateMultipartError
	}

	uploadID := m.UploadID
	if uploadID == "" {
		uploadID = "mock-upload-" + uuid.New().String()
	}

	return &awss3.CreateMultipartUploadOutput{
		UploadId: aws.String(uploadID),
	}, nil
}

// CompleteMultipartUpload implements S3Client
func (m *MockS3Client) CompleteMultipartUpload(ctx context.Context, input *awss3.CompleteMultipartUploadInput, opts ...func(*awss3.Options)) (*awss3.CompleteMultipartUploadOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	partsCount := 0
	if input.MultipartUpload != nil {
		partsCount = len(input.MultipartUpload.Parts)
	}

	m.CompleteCalls = append(m.CompleteCalls, CompleteCall{
		Bucket:   aws.ToString(input.Bucket),
		Key:      aws.ToString(input.Key),
		UploadID: aws.ToString(input.UploadId),
		Parts:    partsCount,
	})

	if m.CompleteError != nil {
		return nil, m.CompleteError
	}

	// Store a placeholder object at the key so Stat/HeadObject works after complete
	key := aws.ToString(input.Key)
	if m.Objects != nil {
		if _, exists := m.Objects[key]; !exists {
			m.Objects[key] = []byte("completed-multipart")
		}
	}

	// Return a mock ETag
	etag := "\"mock-etag-" + uuid.New().String() + "\""
	return &awss3.CompleteMultipartUploadOutput{
		ETag: aws.String(etag),
	}, nil
}

// AbortMultipartUpload implements S3Client
func (m *MockS3Client) AbortMultipartUpload(ctx context.Context, input *awss3.AbortMultipartUploadInput, opts ...func(*awss3.Options)) (*awss3.AbortMultipartUploadOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.AbortCalls = append(m.AbortCalls, AbortCall{
		Bucket:   aws.ToString(input.Bucket),
		Key:      aws.ToString(input.Key),
		UploadID: aws.ToString(input.UploadId),
	})

	if m.AbortError != nil {
		return nil, m.AbortError
	}

	return &awss3.AbortMultipartUploadOutput{}, nil
}

// HeadObject implements S3Client
func (m *MockS3Client) HeadObject(ctx context.Context, input *awss3.HeadObjectInput, opts ...func(*awss3.Options)) (*awss3.HeadObjectOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.HeadObjectError != nil {
		return nil, m.HeadObjectError
	}

	key := aws.ToString(input.Key)
	data, ok := m.Objects[key]
	if !ok {
		return nil, fmt.Errorf("NoSuchKey: object %s not found", key)
	}

	size := int64(len(data))
	return &awss3.HeadObjectOutput{
		ContentLength: &size,
	}, nil
}

// PutObject implements S3Client
func (m *MockS3Client) PutObject(ctx context.Context, input *awss3.PutObjectInput, opts ...func(*awss3.Options)) (*awss3.PutObjectOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	key := aws.ToString(input.Key)
	m.PutObjectCalls = append(m.PutObjectCalls, PutObjectCall{
		Bucket: aws.ToString(input.Bucket),
		Key:    key,
	})

	if input.Body != nil {
		data, err := io.ReadAll(input.Body)
		if err != nil {
			return nil, err
		}
		m.Objects[key] = data
	} else {
		m.Objects[key] = []byte{}
	}

	return &awss3.PutObjectOutput{}, nil
}

// CopyObject implements S3Client
func (m *MockS3Client) CopyObject(ctx context.Context, input *awss3.CopyObjectInput, opts ...func(*awss3.Options)) (*awss3.CopyObjectOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	if m.CopyObjectError != nil {
		return nil, m.CopyObjectError
	}

	// CopySource is "bucket/key"
	copySource := aws.ToString(input.CopySource)
	// Strip bucket prefix to get key
	parts := strings.SplitN(copySource, "/", 2)
	srcKey := copySource
	if len(parts) == 2 {
		srcKey = parts[1]
	}

	data, ok := m.Objects[srcKey]
	if !ok {
		return nil, fmt.Errorf("NoSuchKey: source object %s not found", srcKey)
	}

	dstKey := aws.ToString(input.Key)
	m.Objects[dstKey] = append([]byte{}, data...)

	return &awss3.CopyObjectOutput{}, nil
}

// DeleteObject implements S3Client
func (m *MockS3Client) DeleteObject(ctx context.Context, input *awss3.DeleteObjectInput, opts ...func(*awss3.Options)) (*awss3.DeleteObjectOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	key := aws.ToString(input.Key)
	delete(m.Objects, key)

	return &awss3.DeleteObjectOutput{}, nil
}

// ListObjectsV2 implements S3Client
func (m *MockS3Client) ListObjectsV2(ctx context.Context, input *awss3.ListObjectsV2Input, opts ...func(*awss3.Options)) (*awss3.ListObjectsV2Output, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	prefix := aws.ToString(input.Prefix)
	delimiter := aws.ToString(input.Delimiter)

	var contents []s3types.Object
	commonPrefixes := map[string]bool{}

	for key, data := range m.Objects {
		if !strings.HasPrefix(key, prefix) {
			continue
		}

		if delimiter != "" {
			// Check if there's a delimiter after the prefix
			rest := strings.TrimPrefix(key, prefix)
			idx := strings.Index(rest, delimiter)
			if idx >= 0 {
				// Has delimiter — this is a common prefix, not a content object
				cp := prefix + rest[:idx+len(delimiter)]
				commonPrefixes[cp] = true
				continue
			}
		}

		size := int64(len(data))
		k := key
		contents = append(contents, s3types.Object{
			Key:  &k,
			Size: &size,
		})
	}

	var cps []s3types.CommonPrefix
	for cp := range commonPrefixes {
		p := cp
		cps = append(cps, s3types.CommonPrefix{Prefix: &p})
	}

	falseVal := false
	return &awss3.ListObjectsV2Output{
		Contents:       contents,
		CommonPrefixes: cps,
		IsTruncated:    &falseVal,
	}, nil
}

// PresignUploadPart implements S3Client
// Returns a mock presigned URL for test server
func (m *MockS3Client) PresignUploadPart(ctx context.Context, input *awss3.UploadPartInput, expires time.Duration) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.UploadPartCalls = append(m.UploadPartCalls, UploadPartCall{
		Bucket:     aws.ToString(input.Bucket),
		Key:        aws.ToString(input.Key),
		UploadID:   aws.ToString(input.UploadId),
		PartNumber: aws.ToInt32(input.PartNumber),
	})

	url := fmt.Sprintf("%s/upload/%s?partNumber=%d&uploadId=%s",
		m.TestServerURL,
		aws.ToString(input.Key),
		aws.ToInt32(input.PartNumber),
		aws.ToString(input.UploadId))

	return url, nil
}

// PresignGetObject implements S3Client
func (m *MockS3Client) PresignGetObject(ctx context.Context, input *awss3.GetObjectInput, expires time.Duration) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.GetObjectCalls = append(m.GetObjectCalls, GetObjectCall{
		Bucket: aws.ToString(input.Bucket),
		Key:    aws.ToString(input.Key),
	})

	url := fmt.Sprintf("%s/get/%s", m.TestServerURL, aws.ToString(input.Key))
	return url, nil
}

// PresignHeadObject implements S3Client
func (m *MockS3Client) PresignHeadObject(ctx context.Context, input *awss3.HeadObjectInput, expires time.Duration) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.HeadObjectCalls = append(m.HeadObjectCalls, HeadObjectCall{
		Bucket: aws.ToString(input.Bucket),
		Key:    aws.ToString(input.Key),
	})

	url := fmt.Sprintf("%s/head/%s", m.TestServerURL, aws.ToString(input.Key))
	return url, nil
}

// PresignPutObject implements S3Client
func (m *MockS3Client) PresignPutObject(ctx context.Context, input *awss3.PutObjectInput, expires time.Duration) (string, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.PutObjectCalls = append(m.PutObjectCalls, PutObjectCall{
		Bucket: aws.ToString(input.Bucket),
		Key:    aws.ToString(input.Key),
	})

	// Also store the body if provided (for PresignPutObject used in tests that also check objects)
	if input.Body != nil {
		key := aws.ToString(input.Key)
		data, _ := io.ReadAll(input.Body)
		m.Objects[key] = data
	}

	url := fmt.Sprintf("%s/put/%s", m.TestServerURL, aws.ToString(input.Key))
	return url, nil
}

// SetObject is a test helper to pre-populate an object in the mock store.
func (m *MockS3Client) SetObject(key string, data []byte) {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.Objects[key] = append([]byte{}, data...)
}

// GetObject implements S3Client
func (m *MockS3Client) GetObject(ctx context.Context, input *awss3.GetObjectInput, opts ...func(*awss3.Options)) (*awss3.GetObjectOutput, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	key := aws.ToString(input.Key)
	data, ok := m.Objects[key]
	if !ok {
		return nil, fmt.Errorf("NoSuchKey: %s", key)
	}

	return &awss3.GetObjectOutput{
		Body:          io.NopCloser(bytes.NewReader(bytes.Clone(data))),
		ContentLength: aws.Int64(int64(len(data))),
	}, nil
}

// GetObjectBytes is a test helper to read an object from the mock store (nil if not found).
func (m *MockS3Client) GetObjectBytes(key string) []byte {
	m.mu.Lock()
	defer m.mu.Unlock()
	data, ok := m.Objects[key]
	if !ok {
		return nil
	}
	return bytes.Clone(data)
}