// Copyright (c) 2015-2023 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"crypto/subtle"
	"encoding/hex"
	"io"
	"net/http"
	"net/url"
	"time"

	"github.com/klauspost/compress/gzhttp"
	"github.com/lithammer/shortuuid/v4"
	miniogo "github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"
	"github.com/minio/mux"
	"github.com/minio/pkg/v3/policy"

	"github.com/minio/minio/internal/auth"
	levent "github.com/minio/minio/internal/config/lambda/event"
	"github.com/minio/minio/internal/hash/sha256"
	xhttp "github.com/minio/minio/internal/http"
	"github.com/minio/minio/internal/logger"
)

func getLambdaEventData(bucket, object string, cred auth.Credentials, r *http.Request) (levent.Event, error) {
	host := globalLocalNodeName
	secure := globalIsTLS
	if globalMinioEndpointURL != nil {
		host = globalMinioEndpointURL.Host
		secure = globalMinioEndpointURL.Scheme == "https"
	}

	duration := time.Until(cred.Expiration)
	if duration > time.Hour || duration < time.Hour {
		// Always limit to 1 hour.
		duration = time.Hour
	}

	clnt, err := miniogo.New(host, &miniogo.Options{
		Creds:     credentials.NewStaticV4(cred.AccessKey, cred.SecretKey, cred.SessionToken),
		Secure:    secure,
		Transport: globalRemoteTargetTransport,
		Region:    globalSite.Region(),
	})
	if err != nil {
		return levent.Event{}, err
	}

	reqParams := url.Values{}
	if partNumberStr := r.Form.Get("partNumber"); partNumberStr != "" {
		reqParams.Set("partNumber", partNumberStr)
	}
	for k := range supportedHeadGetReqParams {
		if v := r.Form.Get(k); v != "" {
			reqParams.Set(k, v)
		}
	}

	extraHeaders := http.Header{}
	u, err := clnt.PresignHeader(r.Context(), http.MethodGet, bucket, object, duration, reqParams, extraHeaders)
	if err != nil {
		return levent.Event{}, err
	}

	ckSum := sha256.Sum256([]byte(cred.AccessKey + u.RawQuery))

	eventData := levent.Event{
		GetObjectContext: &levent.GetObjectContext{
			InputS3URL:  u.String(),
			OutputRoute: shortuuid.New(),
			OutputToken: hex.EncodeToString(ckSum[:]),
		},
		UserRequest: levent.UserRequest{
			URL:     r.URL.String(),
			Headers: r.Header.Clone(),
		},
		UserIdentity: levent.Identity{
			Type:        "IAMUser",
			PrincipalID: cred.ParentUser,
			AccessKeyID: cred.AccessKey,
		},
	}
	return eventData, nil
}

var statusTextToCode = map[string]int{
	"Continue":                        http.StatusContinue,
	"Switching Protocols":             http.StatusSwitchingProtocols,
	"Processing":                      http.StatusProcessing,
	"Early Hints":                     http.StatusEarlyHints,
	"OK":                              http.StatusOK,
	"Created":                         http.StatusCreated,
	"Accepted":                        http.StatusAccepted,
	"Non-Authoritative Information":   http.StatusNonAuthoritativeInfo,
	"No Content":                      http.StatusNoContent,
	"Reset Content":                   http.StatusResetContent,
	"Partial Content":                 http.StatusPartialContent,
	"Multi-Status":                    http.StatusMultiStatus,
	"Already Reported":                http.StatusAlreadyReported,
	"IM Used":                         http.StatusIMUsed,
	"Multiple Choices":                http.StatusMultipleChoices,
	"Moved Permanently":               http.StatusMovedPermanently,
	"Found":                           http.StatusFound,
	"See Other":                       http.StatusSeeOther,
	"Not Modified":                    http.StatusNotModified,
	"Use Proxy":                       http.StatusUseProxy,
	"Temporary Redirect":              http.StatusTemporaryRedirect,
	"Permanent Redirect":              http.StatusPermanentRedirect,
	"Bad Request":                     http.StatusBadRequest,
	"Unauthorized":                    http.StatusUnauthorized,
	"Payment Required":                http.StatusPaymentRequired,
	"Forbidden":                       http.StatusForbidden,
	"Not Found":                       http.StatusNotFound,
	"Method Not Allowed":              http.StatusMethodNotAllowed,
	"Not Acceptable":                  http.StatusNotAcceptable,
	"Proxy Authentication Required":   http.StatusProxyAuthRequired,
	"Request Timeout":                 http.StatusRequestTimeout,
	"Conflict":                        http.StatusConflict,
	"Gone":                            http.StatusGone,
	"Length Required":                 http.StatusLengthRequired,
	"Precondition Failed":             http.StatusPreconditionFailed,
	"Request Entity Too Large":        http.StatusRequestEntityTooLarge,
	"Request URI Too Long":            http.StatusRequestURITooLong,
	"Unsupported Media Type":          http.StatusUnsupportedMediaType,
	"Requested Range Not Satisfiable": http.StatusRequestedRangeNotSatisfiable,
	"Expectation Failed":              http.StatusExpectationFailed,
	"I'm a teapot":                    http.StatusTeapot,
	"Misdirected Request":             http.StatusMisdirectedRequest,
	"Unprocessable Entity":            http.StatusUnprocessableEntity,
	"Locked":                          http.StatusLocked,
	"Failed Dependency":               http.StatusFailedDependency,
	"Too Early":                       http.StatusTooEarly,
	"Upgrade Required":                http.StatusUpgradeRequired,
	"Precondition Required":           http.StatusPreconditionRequired,
	"Too Many Requests":               http.StatusTooManyRequests,
	"Request Header Fields Too Large": http.StatusRequestHeaderFieldsTooLarge,
	"Unavailable For Legal Reasons":   http.StatusUnavailableForLegalReasons,
	"Internal Server Error":           http.StatusInternalServerError,
	"Not Implemented":                 http.StatusNotImplemented,
	"Bad Gateway":                     http.StatusBadGateway,
	"Service Unavailable":             http.StatusServiceUnavailable,
	"Gateway Timeout":                 http.StatusGatewayTimeout,
	"HTTP Version Not Supported":      http.StatusHTTPVersionNotSupported,
	"Variant Also Negotiates":         http.StatusVariantAlsoNegotiates,
	"Insufficient Storage":            http.StatusInsufficientStorage,
	"Loop Detected":                   http.StatusLoopDetected,
	"Not Extended":                    http.StatusNotExtended,
	"Network Authentication Required": http.StatusNetworkAuthenticationRequired,
}

// StatusCode returns a HTTP Status code for the HTTP text. It returns -1
// if the text is unknown.
func StatusCode(text string) int {
	if code, ok := statusTextToCode[text]; ok {
		return code
	}
	return -1
}

func fwdHeadersToS3(h http.Header, w http.ResponseWriter) {
	const trim = "x-amz-fwd-header-"
	for k, v := range h {
		if stringsHasPrefixFold(k, trim) {
			w.Header()[k[len(trim):]] = v
		}
	}
}

func fwdStatusToAPIError(resp *http.Response) *APIError {
	if status := resp.Header.Get(xhttp.AmzFwdStatus); status != "" && StatusCode(status) > -1 {
		apiErr := &APIError{
			HTTPStatusCode: StatusCode(status),
			Description:    resp.Header.Get(xhttp.AmzFwdErrorMessage),
			Code:           resp.Header.Get(xhttp.AmzFwdErrorCode),
		}
		if apiErr.HTTPStatusCode == http.StatusOK {
			return nil
		}
		return apiErr
	}
	return nil
}

// GetObjectLambdaHandler - GET Object with transformed data via lambda functions
// ----------
// This implementation of the GET operation applies lambda functions and returns the
// response generated via the lambda functions. To use this API, you must have READ access
// to the object.
func (api objectAPIHandlers) GetObjectLambdaHandler(w http.ResponseWriter, r *http.Request) {
	ctx := newContext(r, w, "GetObjectLambda")

	defer logger.AuditLog(ctx, w, r, mustGetClaimsFromToken(r))

	objectAPI := api.ObjectAPI()
	if objectAPI == nil {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrServerNotInitialized), r.URL)
		return
	}

	vars := mux.Vars(r)
	bucket := vars["bucket"]
	object, err := unescapePath(vars["object"])
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}

	// Check for auth type to return S3 compatible error.
	cred, _, s3Error := checkRequestAuthTypeCredential(ctx, r, policy.GetObjectAction)
	if s3Error != ErrNone {
		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Error), r.URL)
		return
	}

	target, err := globalLambdaTargetList.Lookup(r.Form.Get("lambdaArn"))
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}

	eventData, err := getLambdaEventData(bucket, object, cred, r)
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}

	resp, err := target.Send(eventData)
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}
	defer resp.Body.Close()

	if eventData.GetObjectContext.OutputRoute != resp.Header.Get(xhttp.AmzRequestRoute) {
		tokenErr := errorCodes.ToAPIErr(ErrInvalidRequest)
		tokenErr.Description = "The request route included in the request is invalid"
		writeErrorResponse(ctx, w, tokenErr, r.URL)
		return
	}

	if subtle.ConstantTimeCompare([]byte(resp.Header.Get(xhttp.AmzRequestToken)), []byte(eventData.GetObjectContext.OutputToken)) != 1 {
		tokenErr := errorCodes.ToAPIErr(ErrInvalidToken)
		tokenErr.Description = "The request token included in the request is invalid"
		writeErrorResponse(ctx, w, tokenErr, r.URL)
		return
	}

	// Set all the relevant lambda forward headers if found.
	fwdHeadersToS3(resp.Header, w)

	if apiErr := fwdStatusToAPIError(resp); apiErr != nil {
		writeErrorResponse(ctx, w, *apiErr, r.URL)
		return
	}

	if resp.StatusCode != http.StatusOK {
		writeErrorResponse(ctx, w, APIError{
			Code:           "LambdaFunctionError",
			HTTPStatusCode: resp.StatusCode,
			Description:    "unexpected failure reported from lambda function",
		}, r.URL)
		return
	}

	if !globalAPIConfig.shouldGzipObjects() {
		w.Header().Set(gzhttp.HeaderNoCompression, "true")
	}

	io.Copy(w, resp.Body)
}
