package http

import (
	"bufio"
	"context"
	"fmt"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/pkg/errors"
	"github.com/projectdiscovery/useragent"

	"github.com/projectdiscovery/gologger"
	"github.com/projectdiscovery/nuclei/v3/pkg/authprovider"
	"github.com/projectdiscovery/nuclei/v3/pkg/fuzz"
	"github.com/projectdiscovery/nuclei/v3/pkg/protocols/common/contextargs"
	"github.com/projectdiscovery/nuclei/v3/pkg/protocols/common/expressions"
	"github.com/projectdiscovery/nuclei/v3/pkg/protocols/common/generators"
	"github.com/projectdiscovery/nuclei/v3/pkg/protocols/common/utils/vardump"
	"github.com/projectdiscovery/nuclei/v3/pkg/protocols/http/race"
	"github.com/projectdiscovery/nuclei/v3/pkg/protocols/http/raw"
	protocolutils "github.com/projectdiscovery/nuclei/v3/pkg/protocols/utils"
	httputil "github.com/projectdiscovery/nuclei/v3/pkg/protocols/utils/http"
	"github.com/projectdiscovery/nuclei/v3/pkg/types"
	"github.com/projectdiscovery/nuclei/v3/pkg/types/scanstrategy"
	"github.com/projectdiscovery/rawhttp"
	"github.com/projectdiscovery/retryablehttp-go"
	errorutil "github.com/projectdiscovery/utils/errors"
	readerutil "github.com/projectdiscovery/utils/reader"
	stringsutil "github.com/projectdiscovery/utils/strings"
	urlutil "github.com/projectdiscovery/utils/url"
)

const (
	ReqURLPatternKey = "req_url_pattern"
)

// ErrEvalExpression
var (
	ErrEvalExpression = errorutil.NewWithTag("expr", "could not evaluate helper expressions")
	ErrUnresolvedVars = errorutil.NewWithFmt("unresolved variables `%v` found in request")
)

// generatedRequest is a single generated request wrapped for a template request
type generatedRequest struct {
	original             *Request
	rawRequest           *raw.Request
	meta                 map[string]interface{}
	pipelinedClient      *rawhttp.PipelineClient
	request              *retryablehttp.Request
	dynamicValues        map[string]interface{}
	interactshURLs       []string
	customCancelFunction context.CancelFunc
	// requestURLPattern tracks unmodified request url pattern without values ( it is used for constant vuln_hash)
	// ex: {{BaseURL}}/api/exp?param={{randstr}}
	requestURLPattern string

	fuzzGeneratedRequest fuzz.GeneratedRequest
}

// setReqURLPattern sets the url request pattern for the generated request
func (gr *generatedRequest) setReqURLPattern(reqURLPattern string) {
	data := strings.Split(reqURLPattern, "\n")
	if len(data) > 1 {
		reqURLPattern = strings.TrimSpace(data[0])
		// this is raw request (if it has 3 parts after strings.Fields then its valid only use 2nd part)
		parts := strings.Fields(reqURLPattern)
		if len(parts) >= 3 {
			// remove first and last and use all in between
			parts = parts[1 : len(parts)-1]
			reqURLPattern = strings.Join(parts, " ")
		}
	} else {
		reqURLPattern = strings.TrimSpace(reqURLPattern)
	}

	// now urlRequestPattern is generated replace preprocessor values with actual placeholders
	// that were used (these are called generated 'constants' and contains {{}} in var name)
	for k, v := range gr.original.options.Constants {
		if strings.HasPrefix(k, "{{") && strings.HasSuffix(k, "}}") {
			// this takes care of all preprocessors ( currently we have randstr and its variations)
			reqURLPattern = strings.ReplaceAll(reqURLPattern, fmt.Sprint(v), k)
		}
	}
	gr.requestURLPattern = reqURLPattern
}

// ApplyAuth applies the auth provider to the generated request
func (g *generatedRequest) ApplyAuth(provider authprovider.AuthProvider) {
	if provider == nil {
		return
	}
	if g.request != nil {
		authStrategies := provider.LookupURLX(g.request.URL)
		for _, strategy := range authStrategies {
			strategy.ApplyOnRR(g.request)
		}
	}
	if g.rawRequest != nil {
		parsed, err := urlutil.ParseAbsoluteURL(g.rawRequest.FullURL, true)
		if err != nil {
			gologger.Warning().Msgf("[authprovider] Could not parse URL %s: %s\n", g.rawRequest.FullURL, err)
			return
		}
		authStrategies := provider.LookupURLX(parsed)
		// here we need to apply it custom because we don't have a standard/official
		// rawhttp request format ( which we probably should have )
		for _, strategy := range authStrategies {
			g.rawRequest.ApplyAuthStrategy(strategy)
		}
	}
}

func (g *generatedRequest) URL() string {
	if g.request != nil {
		return g.request.URL.String()
	}
	if g.rawRequest != nil {
		return g.rawRequest.FullURL
	}
	return ""
}

// Total returns the total number of requests for the generator
func (r *requestGenerator) Total() int {
	if r.payloadIterator != nil {
		return len(r.request.Raw) * r.payloadIterator.Remaining()
	}
	return len(r.request.Path)
}

// Make creates a http request for the provided input.
// It returns ErrNoMoreRequests as error when all the requests have been exhausted.
func (r *requestGenerator) Make(ctx context.Context, input *contextargs.Context, reqData string, payloads, dynamicValues map[string]interface{}) (gr *generatedRequest, err error) {
	origReqData := reqData
	defer func() {
		if gr != nil {
			gr.setReqURLPattern(origReqData)
		}
	}()
	// value of `reqData` depends on the type of request specified in template
	// 1. If request is raw request =  reqData contains raw request (i.e http request dump)
	// 2. If request is Normal ( simply put not a raw request) (Ex: with placeholders `path`) = reqData contains relative path

	// add template context values to dynamicValues (this takes care of self-contained and other types of requests)
	// Note: `iterate-all` and flow are mutually exclusive. flow uses templateCtx and iterate-all uses dynamicValues
	if r.request.options.HasTemplateCtx(input.MetaInput) {
		// skip creating template context if not available
		dynamicValues = generators.MergeMaps(dynamicValues, r.request.options.GetTemplateCtx(input.MetaInput).GetAll())
	}
	if r.request.SelfContained {
		return r.makeSelfContainedRequest(ctx, reqData, payloads, dynamicValues)
	}
	isRawRequest := len(r.request.Raw) > 0
	// replace interactsh variables with actual interactsh urls
	if r.options.Interactsh != nil {
		reqData, r.interactshURLs = r.options.Interactsh.Replace(reqData, []string{})
		for payloadName, payloadValue := range payloads {
			payloads[payloadName], r.interactshURLs = r.options.Interactsh.Replace(types.ToString(payloadValue), r.interactshURLs)
		}
	} else {
		for payloadName, payloadValue := range payloads {
			payloads[payloadName] = types.ToStringNSlice(payloadValue)
		}
	}

	// Parse target url
	parsed, err := urlutil.ParseAbsoluteURL(input.MetaInput.Input, false)
	if err != nil {
		return nil, err
	}

	// Non-Raw Requests ex `{{BaseURL}}/somepath` may or maynot have slash after variable and the same is the case for
	// target url to avoid inconsistencies extra slash if exists has to removed from default variables
	hasTrailingSlash := false
	if !isRawRequest {
		// if path contains port ex: {{BaseURL}}:8080 use port specified in reqData
		parsed, reqData = httputil.UpdateURLPortFromPayload(parsed, reqData)
		hasTrailingSlash = httputil.HasTrailingSlash(reqData)
	}

	// defaultreqvars are vars generated from request/input ex: {{baseURL}}, {{Host}} etc
	// contextargs generate extra vars that may/may not be available always (ex: "ip")
	defaultReqVars := protocolutils.GenerateVariables(parsed, hasTrailingSlash, contextargs.GenerateVariables(input))
	// optionvars are vars passed from CLI or env variables
	optionVars := generators.BuildPayloadFromOptions(r.request.options.Options)

	variablesMap, interactURLs := r.options.Variables.EvaluateWithInteractsh(generators.MergeMaps(defaultReqVars, optionVars), r.options.Interactsh)
	if len(interactURLs) > 0 {
		r.interactshURLs = append(r.interactshURLs, interactURLs...)
	}
	// allVars contains all variables from all sources
	allVars := generators.MergeMaps(dynamicValues, defaultReqVars, optionVars, variablesMap, r.options.Constants)

	// Evaluate payload variables
	// eg: payload variables can be username: jon.doe@{{Hostname}}
	for payloadName, payloadValue := range payloads {
		payloads[payloadName], err = expressions.Evaluate(types.ToString(payloadValue), allVars)
		if err != nil {
			return nil, ErrEvalExpression.Wrap(err).WithTag("http")
		}
	}
	// finalVars contains allVars and any generator/fuzzing specific payloads
	// payloads used in generator should be given the most preference
	finalVars := generators.MergeMaps(allVars, payloads)

	if vardump.EnableVarDump {
		gologger.Debug().Msgf("HTTP Protocol request variables: %s\n", vardump.DumpVariables(finalVars))
	}

	// Note: If possible any changes to current logic (i.e evaluate -> then parse URL)
	// should be avoided since it is dependent on `urlutil` core logic

	// Evaluate (replace) variable with final values
	reqData, err = expressions.Evaluate(reqData, finalVars)
	if err != nil {
		return nil, ErrEvalExpression.Wrap(err).WithTag("http")
	}

	if isRawRequest {
		return r.generateRawRequest(ctx, reqData, parsed, finalVars, payloads)
	}

	reqURL, err := urlutil.ParseAbsoluteURL(reqData, true)
	if err != nil {
		return nil, errorutil.NewWithTag("http", "failed to parse url %v while creating http request", reqData)
	}
	// while merging parameters first preference is given to target params
	finalparams := parsed.Params
	finalparams.Merge(reqURL.Params.Encode())
	reqURL.Params = finalparams
	return r.generateHttpRequest(ctx, reqURL, finalVars, payloads)
}

// selfContained templates do not need/use target data and all values i.e {{Hostname}} , {{BaseURL}} etc are already available
// in template . makeSelfContainedRequest parses and creates variables map and then creates corresponding http request or raw request
func (r *requestGenerator) makeSelfContainedRequest(ctx context.Context, data string, payloads, dynamicValues map[string]interface{}) (*generatedRequest, error) {
	isRawRequest := r.request.isRaw()

	values := generators.MergeMaps(
		generators.BuildPayloadFromOptions(r.request.options.Options),
		dynamicValues,
		payloads, // payloads should override other variables in case of duplicate vars
	)
	// adds all variables from `variables` section in template
	variablesMap := r.request.options.Variables.Evaluate(values)
	values = generators.MergeMaps(variablesMap, values)

	signerVars := GetDefaultSignerVars(r.request.Signature.Value)
	// this will ensure that default signer variables are overwritten by other variables
	values = generators.MergeMaps(signerVars, values, r.options.Constants)

	// priority of variables is as follows (from low to high) for self contained templates
	// default signer vars < variables <  cli vars  < payload < dynamic values < constants

	// evaluate request
	data, err := expressions.Evaluate(data, values)
	if err != nil {
		return nil, ErrEvalExpression.Wrap(err).WithTag("self-contained")
	}
	// If the request is a raw request, get the URL from the request
	// header and use it to make the request.
	if isRawRequest {
		// Get the hostname from the URL section to build the request.
		reader := bufio.NewReader(strings.NewReader(data))
	read_line:
		s, err := reader.ReadString('\n')
		if err != nil {
			return nil, fmt.Errorf("could not read request: %w", err)
		}
		// ignore all annotations
		if stringsutil.HasPrefixAny(s, "@") {
			goto read_line
		}

		parts := strings.Split(s, " ")
		if len(parts) < 3 {
			return nil, fmt.Errorf("malformed request supplied")
		}

		if err := expressions.ContainsUnresolvedVariables(parts[1]); err != nil && !r.request.SkipVariablesCheck {
			return nil, ErrUnresolvedVars.Msgf(parts[1])
		}

		parsed, err := urlutil.ParseURL(parts[1], true)
		if err != nil {
			return nil, fmt.Errorf("could not parse request URL: %w", err)
		}
		values = generators.MergeMaps(
			generators.MergeMaps(dynamicValues, protocolutils.GenerateVariables(parsed, false, nil)),
			values,
		)
		// Evaluate (replace) variable with final values
		data, err = expressions.Evaluate(data, values)
		if err != nil {
			return nil, ErrEvalExpression.Wrap(err).WithTag("self-contained", "raw")
		}
		return r.generateRawRequest(ctx, data, parsed, values, payloads)
	}
	if err := expressions.ContainsUnresolvedVariables(data); err != nil && !r.request.SkipVariablesCheck {
		// early exit: if there are any unresolved variables in `path` after evaluation
		// then return early since this will definitely fail
		return nil, ErrUnresolvedVars.Msgf(data)
	}

	urlx, err := urlutil.ParseURL(data, true)
	if err != nil {
		return nil, errorutil.NewWithErr(err).Msgf("failed to parse %v in self contained request", data).WithTag("self-contained")
	}
	return r.generateHttpRequest(ctx, urlx, values, payloads)
}

// generateHttpRequest generates http request from request data from template and variables
// finalVars = contains all variables including generator and protocol specific variables
// generatorValues = contains variables used in fuzzing or other generator specific values
func (r *requestGenerator) generateHttpRequest(ctx context.Context, urlx *urlutil.URL, finalVars, generatorValues map[string]interface{}) (*generatedRequest, error) {
	method, err := expressions.Evaluate(r.request.Method.String(), finalVars)
	if err != nil {
		return nil, ErrEvalExpression.Wrap(err).Msgf("failed to evaluate while generating http request")
	}
	// Build a request on the specified URL
	req, err := retryablehttp.NewRequestFromURLWithContext(ctx, method, urlx, nil)
	if err != nil {
		return nil, err
	}

	request, err := r.fillRequest(req, finalVars)
	if err != nil {
		return nil, err
	}
	return &generatedRequest{request: request, meta: generatorValues, original: r.request, dynamicValues: finalVars, interactshURLs: r.interactshURLs}, nil
}

// generateRawRequest generates Raw Request from request data from template and variables
// finalVars = contains all variables including generator and protocol specific variables
// generatorValues = contains variables used in fuzzing or other generator specific values
func (r *requestGenerator) generateRawRequest(ctx context.Context, rawRequest string, baseURL *urlutil.URL, finalVars, generatorValues map[string]interface{}) (*generatedRequest, error) {

	var rawRequestData *raw.Request
	var err error
	if r.request.SelfContained {
		// in self contained requests baseURL is extracted from raw request itself
		rawRequestData, err = raw.ParseRawRequest(rawRequest, r.request.Unsafe)
	} else {
		rawRequestData, err = raw.Parse(rawRequest, baseURL, r.request.Unsafe, r.request.DisablePathAutomerge)
	}
	if err != nil {
		return nil, errorutil.NewWithErr(err).Msgf("failed to parse raw request")
	}

	// Unsafe option uses rawhttp library
	if r.request.Unsafe {
		if len(r.options.Options.CustomHeaders) > 0 {
			_ = rawRequestData.TryFillCustomHeaders(r.options.Options.CustomHeaders)
		}
		if rawRequestData.Data != "" && !stringsutil.EqualFoldAny(rawRequestData.Method, http.MethodHead, http.MethodGet) && rawRequestData.Headers["Transfer-Encoding"] != "chunked" {
			rawRequestData.Headers["Content-Length"] = strconv.Itoa(len(rawRequestData.Data))
		}
		unsafeReq := &generatedRequest{rawRequest: rawRequestData, meta: generatorValues, original: r.request, interactshURLs: r.interactshURLs}
		return unsafeReq, nil
	}
	urlx, err := urlutil.ParseAbsoluteURL(rawRequestData.FullURL, true)
	if err != nil {
		return nil, errorutil.NewWithErr(err).Msgf("failed to create request with url %v got %v", rawRequestData.FullURL, err).WithTag("raw")
	}
	req, err := retryablehttp.NewRequestFromURLWithContext(ctx, rawRequestData.Method, urlx, rawRequestData.Data)
	if err != nil {
		return nil, err
	}

	// force transfer encoding if conditions are met
	if len(rawRequestData.Data) > 0 && req.Header.Get("Transfer-Encoding") != "chunked" && !stringsutil.EqualFoldAny(rawRequestData.Method, http.MethodGet, http.MethodHead) {
		req.ContentLength = int64(len(rawRequestData.Data))
	}

	// override the body with a new one that will be used to read the request body in parallel threads
	// for race condition testing
	if r.request.Threads > 0 && r.request.Race {
		req.Body = race.NewOpenGateWithTimeout(req.Body, time.Duration(2)*time.Second)
	}
	for key, value := range rawRequestData.Headers {
		if key == "" {
			continue
		}
		req.Header[key] = []string{value}
		if key == "Host" {
			req.Host = value
		}
	}
	request, err := r.fillRequest(req, finalVars)
	if err != nil {
		return nil, err
	}

	generatedRequest := &generatedRequest{
		request:        request,
		meta:           generatorValues,
		original:       r.request,
		dynamicValues:  finalVars,
		interactshURLs: r.interactshURLs,
	}

	if reqWithOverrides, hasAnnotations := r.request.parseAnnotations(rawRequest, req); hasAnnotations {
		generatedRequest.request = reqWithOverrides.request
		generatedRequest.customCancelFunction = reqWithOverrides.cancelFunc
		generatedRequest.interactshURLs = append(generatedRequest.interactshURLs, reqWithOverrides.interactshURLs...)
	}

	return generatedRequest, nil
}

// fillRequest fills various headers in the request with values
func (r *requestGenerator) fillRequest(req *retryablehttp.Request, values map[string]interface{}) (*retryablehttp.Request, error) {
	// Set the header values requested
	for header, value := range r.request.Headers {
		if r.options.Interactsh != nil {
			value, r.interactshURLs = r.options.Interactsh.Replace(value, r.interactshURLs)
		}
		value, err := expressions.Evaluate(value, values)
		if err != nil {
			return nil, ErrEvalExpression.Wrap(err).Msgf("failed to evaluate while adding headers to request")
		}
		req.Header[header] = []string{value}
		if header == "Host" {
			req.Host = value
		}
	}

	// In case of multiple threads the underlying connection should remain open to allow reuse
	if r.request.Threads <= 0 && req.Header.Get("Connection") == "" && r.options.Options.ScanStrategy != scanstrategy.HostSpray.String() {
		req.Close = true
	}

	// Check if the user requested a request body
	if r.request.Body != "" {
		body := r.request.Body
		if r.options.Interactsh != nil {
			body, r.interactshURLs = r.options.Interactsh.Replace(r.request.Body, r.interactshURLs)
		}
		body, err := expressions.Evaluate(body, values)
		if err != nil {
			return nil, ErrEvalExpression.Wrap(err)
		}
		bodyReader, err := readerutil.NewReusableReadCloser([]byte(body))
		if err != nil {
			return nil, errors.Wrap(err, "failed to create reusable reader for request body")
		}
		req.Body = bodyReader
	}
	if !r.request.Unsafe {
		userAgent := useragent.PickRandom()
		httputil.SetHeader(req, "User-Agent", userAgent.Raw)
	}

	// Only set these headers on non-raw requests
	if len(r.request.Raw) == 0 && !r.request.Unsafe {
		httputil.SetHeader(req, "Accept", "*/*")
		httputil.SetHeader(req, "Accept-Language", "en")
	}

	if !LeaveDefaultPorts {
		switch {
		case req.URL.Scheme == "http" && strings.HasSuffix(req.Host, ":80"):
			req.Host = strings.TrimSuffix(req.Host, ":80")
		case req.URL.Scheme == "https" && strings.HasSuffix(req.Host, ":443"):
			req.Host = strings.TrimSuffix(req.Host, ":443")
		}
	}

	if r.request.DigestAuthUsername != "" {
		req.Auth = &retryablehttp.Auth{
			Type:     retryablehttp.DigestAuth,
			Username: r.request.DigestAuthUsername,
			Password: r.request.DigestAuthPassword,
		}
	}

	return req, nil
}
