// Copyright 2016-2018, Pulumi Corporation.
//
// 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 client

import (
	"bytes"
	"compress/gzip"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"reflect"
	"runtime"
	"strings"

	"github.com/pulumi/pulumi/pkg/diag"

	"github.com/google/go-querystring/query"
	"github.com/opentracing/opentracing-go"
	"github.com/pkg/errors"

	"github.com/pulumi/pulumi/pkg/apitype"
	"github.com/pulumi/pulumi/pkg/util/contract"
	"github.com/pulumi/pulumi/pkg/util/httputil"
	"github.com/pulumi/pulumi/pkg/util/logging"
	"github.com/pulumi/pulumi/pkg/util/tracing"
	"github.com/pulumi/pulumi/pkg/version"
)

const (
	apiRequestLogLevel       = 10 // log level for logging API requests and responses
	apiRequestDetailLogLevel = 11 // log level for logging extra details about API requests and responses
)

// StackIdentifier is the set of data needed to identify a Pulumi Cloud stack.
type StackIdentifier struct {
	Owner   string
	Project string
	Stack   string
}

// UpdateIdentifier is the set of data needed to identify an update to a Pulumi Cloud stack.
type UpdateIdentifier struct {
	StackIdentifier

	UpdateKind apitype.UpdateKind
	UpdateID   string
}

// accessTokenKind is enumerates the various types of access token used with the Pulumi API. These kinds correspond
// directly to the "method" piece of an HTTP `Authorization` header.
type accessTokenKind string

const (
	// accessTokenKindAPIToken denotes a standard Pulumi API token.
	accessTokenKindAPIToken accessTokenKind = "token"
	// accessTokenKindUpdateToken denotes an update lease token.
	accessTokenKindUpdateToken accessTokenKind = "update-token"
)

// accessToken is an abstraction over the two different kinds of access tokens used by the Pulumi API.
type accessToken interface {
	Kind() accessTokenKind
	String() string
}

type httpCallOptions struct {
	// RetryAllMethods allows non-GET calls to be retried if the server fails to return a response.
	RetryAllMethods bool

	// GzipCompress compresses the request using gzip before sending it.
	GzipCompress bool
}

// apiAccessToken is an implementation of accessToken for Pulumi API tokens (i.e. tokens of kind
// accessTokenKindAPIToken)
type apiAccessToken string

func (apiAccessToken) Kind() accessTokenKind {
	return accessTokenKindAPIToken
}

func (t apiAccessToken) String() string {
	return string(t)
}

// updateAccessToken is an implementation of accessToken for update lease tokens (i.e. tokens of kind
// accessTokenKindUpdateToken)
type updateAccessToken string

func (updateAccessToken) Kind() accessTokenKind {
	return accessTokenKindUpdateToken
}

func (t updateAccessToken) String() string {
	return string(t)
}

// pulumiAPICall makes an HTTP request to the Pulumi API.
func pulumiAPICall(ctx context.Context, d diag.Sink, cloudAPI, method, path string, body []byte, tok accessToken,
	opts httpCallOptions) (string, *http.Response, error) {

	// Normalize URL components
	cloudAPI = strings.TrimSuffix(cloudAPI, "/")
	path = cleanPath(path)

	url := fmt.Sprintf("%s%s", cloudAPI, path)
	var bodyReader io.Reader
	if opts.GzipCompress {
		// If we're being asked to compress the payload, go ahead and do it here to an intermediate buffer.
		//
		// If this becomes a performance bottleneck, we may want to consider marshaling json directly to this
		// gzip.Writer instead of marshaling to a byte array and compressing it to another buffer.
		logging.V(apiRequestDetailLogLevel).Infoln("compressing payload using gzip")
		var buf bytes.Buffer
		writer := gzip.NewWriter(&buf)
		defer contract.IgnoreClose(writer)
		if _, err := writer.Write(body); err != nil {
			return "", nil, errors.Wrapf(err, "compressing payload")
		}

		// gzip.Writer will not actually write anything unless it is flushed.
		if err := writer.Flush(); err != nil {
			return "", nil, errors.Wrapf(err, "flushing compressed payload")
		}

		logging.V(apiRequestDetailLogLevel).Infof("gzip compression ratio: %f, original size: %d bytes",
			float64(len(body))/float64(len(buf.Bytes())), len(body))
		bodyReader = &buf
	} else {
		bodyReader = bytes.NewReader(body)
	}

	req, err := http.NewRequest(method, url, bodyReader)
	if err != nil {
		return "", nil, errors.Wrapf(err, "creating new HTTP request")
	}

	requestSpan, requestContext := opentracing.StartSpanFromContext(ctx, getEndpointName(method, path),
		opentracing.Tag{Key: "method", Value: method},
		opentracing.Tag{Key: "path", Value: path},
		opentracing.Tag{Key: "api", Value: cloudAPI},
		opentracing.Tag{Key: "retry", Value: opts.RetryAllMethods})
	defer requestSpan.Finish()

	req = req.WithContext(requestContext)
	req.Header.Set("Content-Type", "application/json")

	// Add a User-Agent header to allow for the backend to make breaking API changes while preserving
	// backwards compatibility.
	userAgent := fmt.Sprintf("pulumi-cli/1 (%s; %s)", version.Version, runtime.GOOS)
	req.Header.Set("User-Agent", userAgent)
	// Specify the specific API version we accept.
	req.Header.Set("Accept", "application/vnd.pulumi+4")

	// Apply credentials if provided.
	if tok.String() != "" {
		req.Header.Set("Authorization", fmt.Sprintf("%s %s", tok.Kind(), tok.String()))
	}

	tracingOptions := tracing.OptionsFromContext(requestContext)
	if tracingOptions.PropagateSpans {
		carrier := opentracing.HTTPHeadersCarrier(req.Header)
		if err = requestSpan.Tracer().Inject(requestSpan.Context(), opentracing.HTTPHeaders, carrier); err != nil {
			logging.Errorf("injecting tracing headers: %v", err)
		}
	}
	if tracingOptions.TracingHeader != "" {
		req.Header.Set("X-Pulumi-Tracing", tracingOptions.TracingHeader)
	}

	// Opt-in to accepting gzip-encoded responses from the service.
	req.Header.Set("Accept-Encoding", "gzip")
	if opts.GzipCompress {
		// If we're sending something that's gzipped, set that header too.
		req.Header.Set("Content-Encoding", "gzip")
	}

	logging.V(apiRequestLogLevel).Infof("Making Pulumi API call: %s", url)
	if logging.V(apiRequestDetailLogLevel) {
		logging.V(apiRequestDetailLogLevel).Infof(
			"Pulumi API call details (%s): headers=%v; body=%v", url, req.Header, string(body))
	}

	var resp *http.Response
	if req.Method == "GET" || opts.RetryAllMethods {
		resp, err = httputil.DoWithRetry(req, http.DefaultClient)
	} else {
		resp, err = http.DefaultClient.Do(req)
	}

	if err != nil {
		return "", nil, errors.Wrapf(err, "performing HTTP request")
	}
	logging.V(apiRequestLogLevel).Infof("Pulumi API call response code (%s): %v", url, resp.Status)

	requestSpan.SetTag("responseCode", resp.Status)

	if warningHeader, ok := resp.Header["X-Pulumi-Warning"]; ok {
		for _, warning := range warningHeader {
			d.Warningf(diag.RawMessage("", warning))
		}
	}

	// For 4xx and 5xx failures, attempt to provide better diagnostics about what may have gone wrong.
	if resp.StatusCode >= 400 && resp.StatusCode <= 599 {
		// 4xx and 5xx responses should be of type ErrorResponse. See if we can unmarshal as that
		// type, and if not just return the raw response text.
		respBody, err := readBody(resp)
		if err != nil {
			return "", nil, errors.Wrapf(
				err, "API call failed (%s), could not read response", resp.Status)
		}

		// Provide a better error if using an authenticated call without having logged in first.
		if resp.StatusCode == 401 && tok.Kind() == accessTokenKindAPIToken && tok.String() == "" {
			return "", nil, errors.New("this command requires logging in; try running 'pulumi login' first")
		}

		var errResp apitype.ErrorResponse
		if err = json.Unmarshal(respBody, &errResp); err != nil {
			errResp.Code = resp.StatusCode
			errResp.Message = strings.TrimSpace(string(respBody))
		}
		return "", nil, &errResp
	}

	return url, resp, nil
}

// pulumiRESTCall calls the Pulumi REST API marshalling reqObj to JSON and using that as
// the request body (use nil for GETs), and if successful, marshalling the responseObj
// as JSON and storing it in respObj (use nil for NoContent). The error return type might
// be an instance of apitype.ErrorResponse, in which case will have the response code.
func pulumiRESTCall(ctx context.Context, diag diag.Sink, cloudAPI, method, path string, queryObj, reqObj,
	respObj interface{}, tok accessToken, opts httpCallOptions) error {

	// Compute query string from query object
	querystring := ""
	if queryObj != nil {
		queryValues, err := query.Values(queryObj)
		if err != nil {
			return errors.Wrapf(err, "marshalling query object as JSON")
		}
		query := queryValues.Encode()
		if len(query) > 0 {
			querystring = "?" + query
		}
	}

	// Compute request body from request object
	var reqBody []byte
	var err error
	if reqObj != nil {
		reqBody, err = json.Marshal(reqObj)
		if err != nil {
			return errors.Wrapf(err, "marshalling request object as JSON")
		}
	}

	// Make API call
	url, resp, err := pulumiAPICall(ctx, diag, cloudAPI, method, path+querystring, reqBody, tok, opts)
	if err != nil {
		return err
	}

	// Read API response
	respBody, err := readBody(resp)
	if err != nil {
		return errors.Wrapf(err, "reading response from API")
	}
	if logging.V(apiRequestDetailLogLevel) {
		logging.V(apiRequestDetailLogLevel).Infof("Pulumi API call response body (%s): %v", url, string(respBody))
	}

	if respObj != nil {
		bytes := reflect.TypeOf([]byte(nil))
		if typ := reflect.TypeOf(respObj); typ == reflect.PtrTo(bytes) {
			// Return the raw bytes of the response body.
			*respObj.(*[]byte) = respBody
		} else if typ == bytes {
			return fmt.Errorf("Can't unmarshal response body to []byte. Try *[]byte")
		} else {
			// Else, unmarshal as JSON.
			if err = json.Unmarshal(respBody, respObj); err != nil {
				return errors.Wrapf(err, "unmarshalling response object")
			}
		}
	}

	return nil
}

// readBody reads the contents of an http.Response into a byte array, returning an error if one occurred while in the
// process of doing so. readBody uses the Content-Encoding of the response to pick the correct reader to use.
func readBody(resp *http.Response) ([]byte, error) {
	contentEncoding, ok := resp.Header["Content-Encoding"]
	defer contract.IgnoreClose(resp.Body)
	if !ok {
		// No header implies that there's no additional encoding on this response.
		return ioutil.ReadAll(resp.Body)
	}

	if len(contentEncoding) > 1 {
		// We only know how to deal with gzip. We can't handle additional encodings layered on top of it.
		return nil, errors.Errorf("can't handle content encodings %v", contentEncoding)
	}

	switch contentEncoding[0] {
	case "x-gzip":
		// The HTTP/1.1 spec recommends we treat x-gzip as an alias of gzip.
		fallthrough
	case "gzip":
		logging.V(apiRequestDetailLogLevel).Infoln("decompressing gzipped response from service")
		reader, err := gzip.NewReader(resp.Body)
		defer contract.IgnoreClose(reader)
		if err != nil {
			return nil, errors.Wrap(err, "reading gzip-compressed body")
		}

		return ioutil.ReadAll(reader)
	default:
		return nil, errors.Errorf("unrecognized encoding %s", contentEncoding[0])
	}
}