package middleware

import (
	"bytes"
	"encoding/xml"
	"fmt"
	"net/http"
	"strconv"
	"sync"

	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/errors"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/logs"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/version"
	"go.opentelemetry.io/otel/trace"
	"go.uber.org/zap"
)

type (
	// ErrorResponse -- error response format.
	ErrorResponse struct {
		XMLName    xml.Name `xml:"Error" json:"-"`
		Code       string
		Message    string
		Key        string `xml:"Key,omitempty" json:"Key,omitempty"`
		BucketName string `xml:"BucketName,omitempty" json:"BucketName,omitempty"`
		Resource   string
		RequestID  string `xml:"RequestId" json:"RequestId"`
		HostID     string `xml:"HostId" json:"HostId"`

		// The region where the bucket is located. This header is returned
		// only in HEAD bucket and ListObjects response.
		Region string `xml:"Region,omitempty" json:"Region,omitempty"`

		// Captures the server string returned in response header.
		Server string `xml:"-" json:"-"`

		// Underlying HTTP status code for the returned error.
		StatusCode int `xml:"-" json:"-"`
	}

	// mimeType represents various MIME types used in API responses.
	mimeType string
)

const (

	// MimeNone means no response type.
	MimeNone mimeType = ""

	// MimeXML means response type is XML.
	MimeXML mimeType = "application/xml"

	hdrServerInfo    = "Server"
	hdrAcceptRanges  = "Accept-Ranges"
	hdrContentType   = "Content-Type"
	hdrContentLength = "Content-Length"
	hdrRetryAfter    = "Retry-After"

	// Response request id.

	// hdrSSE is the general AWS SSE HTTP header key.
	hdrSSE = "X-Amz-Server-Side-Encryption"

	// hdrSSECustomerKey is the HTTP header key referencing the
	// SSE-C client-provided key..
	hdrSSECustomerKey = hdrSSE + "-Customer-Key"

	// hdrSSECopyKey is the HTTP header key referencing the SSE-C
	// client-provided key for SSE-C copy requests.
	hdrSSECopyKey = "X-Amz-Copy-Source-Server-Side-Encryption-Customer-Key"
)

var (
	xmlHeader = []byte(xml.Header)
)

// Non exhaustive list of AWS S3 standard error responses -
// http://docs.aws.amazon.com/AmazonS3/latest/API/ErrorResponses.html
var s3ErrorResponseMap = map[string]string{
	"AccessDenied":                      "Access Denied.",
	"BadDigest":                         "The Content-Md5 you specified did not match what we received.",
	"EntityTooSmall":                    "Your proposed upload is smaller than the minimum allowed object size.",
	"EntityTooLarge":                    "Your proposed upload exceeds the maximum allowed object size.",
	"IncompleteBody":                    "You did not provide the number of bytes specified by the Content-Length HTTP header.",
	"InternalError":                     "We encountered an internal error, please try again.",
	"InvalidAccessKeyId":                "The access key ID you provided does not exist in our records.",
	"InvalidBucketName":                 "The specified bucket is not valid.",
	"InvalidDigest":                     "The Content-Md5 you specified is not valid.",
	"InvalidRange":                      "The requested range is not satisfiable",
	"MalformedXML":                      "The XML you provided was not well-formed or did not validate against our published schema.",
	"MissingContentLength":              "You must provide the Content-Length HTTP header.",
	"MissingContentMD5":                 "Missing required header for this request: Content-Md5.",
	"MissingRequestBodyError":           "Request body is empty.",
	"NoSuchBucket":                      "The specified bucket does not exist.",
	"NoSuchBucketPolicy":                "The bucket policy does not exist",
	"NoSuchKey":                         "The specified key does not exist.",
	"NoSuchUpload":                      "The specified multipart upload does not exist. The upload ID may be invalid, or the upload may have been aborted or completed.",
	"NotImplemented":                    "A header you provided implies functionality that is not implemented",
	"PreconditionFailed":                "At least one of the pre-conditions you specified did not hold",
	"RequestTimeTooSkewed":              "The difference between the request time and the server's time is too large.",
	"SignatureDoesNotMatch":             "The request signature we calculated does not match the signature you provided. Check your key and signing method.",
	"MethodNotAllowed":                  "The specified method is not allowed against this resource.",
	"InvalidPart":                       "One or more of the specified parts could not be found.",
	"InvalidPartOrder":                  "The list of parts was not in ascending order. The parts list must be specified in order by part number.",
	"InvalidObjectState":                "The operation is not valid for the current state of the object.",
	"AuthorizationHeaderMalformed":      "The authorization header is malformed; the region is wrong.",
	"MalformedPOSTRequest":              "The body of your POST request is not well-formed multipart/form-data.",
	"BucketNotEmpty":                    "The bucket you tried to delete is not empty",
	"AllAccessDisabled":                 "All access to this bucket has been disabled.",
	"MalformedPolicy":                   "Policy has invalid resource.",
	"MissingFields":                     "Missing fields in request.",
	"AuthorizationQueryParametersError": "Error parsing the X-Amz-Credential parameter; the Credential is mal-formed; expecting \"<YOUR-AKID>/YYYYMMDD/REGION/SERVICE/aws4_request\".",
	"MalformedDate":                     "Invalid date format header, expected to be in ISO8601, RFC1123 or RFC1123Z time format.",
	"BucketAlreadyOwnedByYou":           "Your previous request to create the named bucket succeeded and you already own it.",
	"InvalidDuration":                   "Duration provided in the request is invalid.",
	"XAmzContentSHA256Mismatch":         "The provided 'x-amz-content-sha256' header does not match what was computed.",
	// Add new API errors here.
}

// WriteErrorResponse writes error headers.
// returns http error code and error in case of failure of response writing.
func WriteErrorResponse(w http.ResponseWriter, reqInfo *ReqInfo, err error) (int, error) {
	code := http.StatusInternalServerError

	if e, ok := err.(errors.Error); ok {
		code = e.HTTPStatusCode

		switch e.Code {
		case "SlowDown", "XFrostFSServerNotInitialized", "XFrostFSReadQuorum", "XFrostFSWriteQuorum":
			// Set retry-after header to indicate user-agents to retry request after 120secs.
			// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After
			w.Header().Set(hdrRetryAfter, "120")
		}
	}

	// Generates error response.
	errorResponse := getAPIErrorResponse(reqInfo, err)
	encodedErrorResponse, err := EncodeResponse(errorResponse)
	if err != nil {
		return 0, fmt.Errorf("encode response: %w", err)
	}
	if err = WriteResponse(w, code, encodedErrorResponse, MimeXML); err != nil {
		return 0, fmt.Errorf("write response: %w", err)
	}
	return code, nil
}

// Write http common headers.
func setCommonHeaders(w http.ResponseWriter) {
	w.Header().Set(hdrServerInfo, version.Server)
	w.Header().Set(hdrAcceptRanges, "bytes")

	// Remove sensitive information
	removeSensitiveHeaders(w.Header())
}

// removeSensitiveHeaders removes confidential encryption
// information -- e.g. the SSE-C key -- from the HTTP headers.
// It has the same semantics as RemoveSensitiveEntries.
func removeSensitiveHeaders(h http.Header) {
	h.Del(hdrSSECustomerKey)
	h.Del(hdrSSECopyKey)
}

// WriteResponse writes given statusCode and response into w (with mType header if set).
func WriteResponse(w http.ResponseWriter, statusCode int, response []byte, mType mimeType) error {
	setCommonHeaders(w)
	if mType != MimeNone {
		w.Header().Set(hdrContentType, string(mType))
	}
	w.Header().Set(hdrContentLength, strconv.Itoa(len(response)))
	w.WriteHeader(statusCode)
	if response == nil {
		return nil
	}

	return WriteResponseBody(w, response)
}

// WriteResponseBody writes response into w.
func WriteResponseBody(w http.ResponseWriter, response []byte) error {
	if _, err := w.Write(response); err != nil {
		return err
	}

	if flusher, ok := w.(http.Flusher); ok {
		flusher.Flush()
	}

	return nil
}

// EncodeResponse encodes the response headers into XML format.
func EncodeResponse(response interface{}) ([]byte, error) {
	var bytesBuffer bytes.Buffer
	bytesBuffer.WriteString(xml.Header)
	if err := xml.NewEncoder(&bytesBuffer).Encode(response); err != nil {
		return nil, err
	}

	return bytesBuffer.Bytes(), nil
}

// EncodeToResponse encodes the response into ResponseWriter.
func EncodeToResponse(w http.ResponseWriter, response interface{}) error {
	w.WriteHeader(http.StatusOK)

	if _, err := w.Write(xmlHeader); err != nil {
		return fmt.Errorf("write headers: %w", err)
	}

	return EncodeToResponseNoHeader(w, response)
}

// EncodeToResponseNoHeader encodes the response into ResponseWriter without
// header status.
func EncodeToResponseNoHeader(w http.ResponseWriter, response interface{}) error {
	if err := xml.NewEncoder(w).Encode(response); err != nil {
		return fmt.Errorf("encode xml response: %w", err)
	}

	return nil
}

// // WriteSuccessResponseXML writes success headers and response if any,
// // with content-type set to `application/xml`.
// func WriteSuccessResponseXML(w http.ResponseWriter, response []byte) {
// 	WriteResponse(w, http.StatusOK, response, MimeXML)
// }

// WriteSuccessResponseHeadersOnly writes HTTP (200) OK response with no data
// to the client.
func WriteSuccessResponseHeadersOnly(w http.ResponseWriter) error {
	return WriteResponse(w, http.StatusOK, nil, MimeNone)
}

// Error -- Returns S3 error string.
func (e ErrorResponse) Error() string {
	if e.Message == "" {
		msg, ok := s3ErrorResponseMap[e.Code]
		if !ok {
			msg = fmt.Sprintf("Error response code %s.", e.Code)
		}
		return msg
	}
	return e.Message
}

// getErrorResponse gets in standard error and resource value and
// provides an encodable populated response values.
func getAPIErrorResponse(info *ReqInfo, err error) ErrorResponse {
	code := "InternalError"
	desc := err.Error()

	if e, ok := err.(errors.Error); ok {
		code = e.Code
		desc = e.Description
	}

	var resource string
	if info.URL != nil {
		resource = info.URL.Path
	}

	return ErrorResponse{
		Code:       code,
		Message:    desc,
		BucketName: info.BucketName,
		Key:        info.ObjectName,
		Resource:   resource,
		RequestID:  info.RequestID,
		HostID:     info.DeploymentID,
	}
}

type logResponseWriter struct {
	sync.Once
	http.ResponseWriter

	statusCode int
}

func (lrw *logResponseWriter) WriteHeader(code int) {
	lrw.Do(func() {
		lrw.statusCode = code
		lrw.ResponseWriter.WriteHeader(code)
	})
}

func (lrw *logResponseWriter) Flush() {
	if f, ok := lrw.ResponseWriter.(http.Flusher); ok {
		f.Flush()
	}
}

func LogSuccessResponse(l *zap.Logger) Func {
	return func(h http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			lw := &logResponseWriter{ResponseWriter: w}

			// here reqInfo doesn't contain bucket name and object name

			// pass execution:
			h.ServeHTTP(lw, r)

			// here reqInfo contains bucket name and object name because of
			// addBucketName and addObjectName middlewares

			// Ignore >400 status codes
			if lw.statusCode >= http.StatusBadRequest {
				return
			}

			ctx := r.Context()
			reqLogger := reqLogOrDefault(ctx, l)
			reqInfo := GetReqInfo(ctx)

			fields := make([]zap.Field, 0, 6)
			fields = append(fields,
				zap.Int("status", lw.statusCode),
				zap.String("description", http.StatusText(lw.statusCode)),
				zap.String("method", reqInfo.API),
			)

			if reqInfo.BucketName != "" {
				fields = append(fields, zap.String("bucket", reqInfo.BucketName))
			}
			if reqInfo.ObjectName != "" {
				fields = append(fields, zap.String("object", reqInfo.ObjectName))
			}
			if reqInfo.User != "" {
				fields = append(fields, zap.String("user", reqInfo.User))
			}

			if traceID, err := trace.TraceIDFromHex(reqInfo.TraceID); err == nil && traceID.IsValid() {
				fields = append(fields, zap.String("trace_id", reqInfo.TraceID))
			}

			reqLogger.Info(logs.RequestEnd, fields...)
		})
	}
}