Implement S3 Style ErrorCodes and Response

This patchset also brings in lot of cleanup in terms of minioapi codebase

pkg/api/minioapi/errors.go

@@ -0,0 +1,170 @@
+package minioapi
+
+import (
+	"encoding/xml"
+	"net/http"
+)
+
+type Error struct {
+	Code           string
+	Description    string
+	HttpStatusCode int
+}
+
+type ErrorResponse struct {
+	XMLName   xml.Name `xml:"Error" json:"-"`
+	Code      string
+	Message   string
+	Resource  string
+	RequestId string
+}
+
+/// Error codes, non exhaustive list
+const (
+	AccessDenied = iota
+	BadDigest
+	BucketAlreadyExists
+	EntityTooSmall
+	EntityTooLarge
+	IncompleteBody
+	InternalError
+	InvalidAccessKeyId
+	InvalidBucketName
+	InvalidDigest
+	InvalidRange
+	MalformedXML
+	MissingContentLength
+	MissingRequestBodyError
+	NoSuchBucket
+	NoSuchKey
+	NoSuchUpload
+	NotImplemented
+	RequestTimeTooSkewed
+	SignatureDoesNotMatch
+	TooManyBuckets
+)
+
+var errorCodeResponse = map[int]Error{
+	AccessDenied: {
+		Code:           "AccessDenied",
+		Description:    "Access Denied",
+		HttpStatusCode: http.StatusForbidden,
+	},
+	BadDigest: {
+		Code:           "BadDigest",
+		Description:    "The Content-MD5 you specified did not match what we received.",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+	BucketAlreadyExists: {
+		Code:           "BucketAlreadyExists",
+		Description:    "The requested bucket name is not available.",
+		HttpStatusCode: http.StatusConflict,
+	},
+	EntityTooSmall: {
+		Code:           "EntityTooSmall",
+		Description:    "Your proposed upload is smaller than the minimum allowed object size.",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+	EntityTooLarge: {
+		Code:           "EntityTooLarge",
+		Description:    "Your proposed upload exceeds the maximum allowed object size.",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+	IncompleteBody: {
+		Code:           "IncompleteBody",
+		Description:    "You did not provide the number of bytes specified by the Content-Length HTTP header",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+	InternalError: {
+		Code:           "InternalError",
+		Description:    "We encountered an internal error, please try again.",
+		HttpStatusCode: http.StatusInternalServerError,
+	},
+	InvalidAccessKeyId: {
+		Code:           "InvalidAccessKeyId",
+		Description:    "The access key Id you provided does not exist in our records.",
+		HttpStatusCode: http.StatusForbidden,
+	},
+	InvalidBucketName: {
+		Code:           "InvalidBucketName",
+		Description:    "The specified bucket is not valid.",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+	InvalidDigest: {
+		Code:           "InvalidDigest",
+		Description:    "The Content-MD5 you specified is not valid.",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+	InvalidRange: {
+		Code:           "InvalidRange",
+		Description:    "The requested range cannot be satisfied.",
+		HttpStatusCode: http.StatusRequestedRangeNotSatisfiable,
+	},
+	MalformedXML: {
+		Code:           "MalformedXML",
+		Description:    "The XML you provided was not well-formed or did not validate against our published schema.",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+	MissingContentLength: {
+		Code:           "MissingContentLength",
+		Description:    "You must provide the Content-Length HTTP header.",
+		HttpStatusCode: http.StatusLengthRequired,
+	},
+	MissingRequestBodyError: {
+		Code:           "MissingRequestBodyError",
+		Description:    "Request body is empty.",
+		HttpStatusCode: http.StatusLengthRequired,
+	},
+	NoSuchBucket: {
+		Code:           "NoSuchBucket",
+		Description:    "The specified bucket does not exist.",
+		HttpStatusCode: http.StatusNotFound,
+	},
+	NoSuchKey: {
+		Code:           "NoSuchKey",
+		Description:    "The specified key does not exist.",
+		HttpStatusCode: http.StatusNotFound,
+	},
+	NoSuchUpload: {
+		Code:           "NoSuchUpload",
+		Description:    "The specified multipart upload does not exist.",
+		HttpStatusCode: http.StatusNotFound,
+	},
+	NotImplemented: {
+		Code:           "NotImplemented",
+		Description:    "A header you provided implies functionality that is not implemented.",
+		HttpStatusCode: http.StatusNotImplemented,
+	},
+	RequestTimeTooSkewed: {
+		Code:           "RequestTimeTooSkewed",
+		Description:    "The difference between the request time and the server's time is too large.",
+		HttpStatusCode: http.StatusForbidden,
+	},
+	SignatureDoesNotMatch: {
+		Code:           "SignatureDoesNotMatch",
+		Description:    "The request signature we calculated does not match the signature you provided.",
+		HttpStatusCode: http.StatusForbidden,
+	},
+	TooManyBuckets: {
+		Code:           "TooManyBuckets",
+		Description:    "You have attempted to create more buckets than allowed.",
+		HttpStatusCode: http.StatusBadRequest,
+	},
+}
+
+// errorCodeError provides errorCode to Error. It returns empty if
+// the code provided is unknown
+func errorCodeError(code int) Error {
+	return errorCodeResponse[code]
+}
+
+func getErrorResponse(err Error, resource string) ErrorResponse {
+	var data = ErrorResponse{}
+	data.Code = err.Code
+	data.Message = err.Description
+	data.Resource = resource
+	// TODO implement this in future
+	data.RequestId = "3LI37"
+
+	return data
+}