package gock

import (
	"compress/gzip"
	"encoding/json"
	"io"
	"io/ioutil"
	"net/http"
	"reflect"
	"regexp"
	"strings"

	"github.com/h2non/parth"
)

// EOL represents the end of line character.
const EOL = 0xa

// BodyTypes stores the supported MIME body types for matching.
// Currently only text-based types.
var BodyTypes = []string{
	"text/html",
	"text/plain",
	"application/json",
	"application/xml",
	"multipart/form-data",
	"application/x-www-form-urlencoded",
}

// BodyTypeAliases stores a generic MIME type by alias.
var BodyTypeAliases = map[string]string{
	"html": "text/html",
	"text": "text/plain",
	"json": "application/json",
	"xml":  "application/xml",
	"form": "multipart/form-data",
	"url":  "application/x-www-form-urlencoded",
}

// CompressionSchemes stores the supported Content-Encoding types for decompression.
var CompressionSchemes = []string{
	"gzip",
}

// MatchMethod matches the HTTP method of the given request.
func MatchMethod(req *http.Request, ereq *Request) (bool, error) {
	return ereq.Method == "" || req.Method == ereq.Method, nil
}

// MatchScheme matches the request URL protocol scheme.
func MatchScheme(req *http.Request, ereq *Request) (bool, error) {
	return ereq.URLStruct.Scheme == "" || req.URL.Scheme == "" || ereq.URLStruct.Scheme == req.URL.Scheme, nil
}

// MatchHost matches the HTTP host header field of the given request.
func MatchHost(req *http.Request, ereq *Request) (bool, error) {
	url := ereq.URLStruct
	if strings.EqualFold(url.Host, req.URL.Host) {
		return true, nil
	}
	if !ereq.Options.DisableRegexpHost {
		return regexp.MatchString(url.Host, req.URL.Host)
	}
	return false, nil
}

// MatchPath matches the HTTP URL path of the given request.
func MatchPath(req *http.Request, ereq *Request) (bool, error) {
	if req.URL.Path == ereq.URLStruct.Path {
		return true, nil
	}
	return regexp.MatchString(ereq.URLStruct.Path, req.URL.Path)
}

// MatchHeaders matches the headers fields of the given request.
func MatchHeaders(req *http.Request, ereq *Request) (bool, error) {
	for key, value := range ereq.Header {
		var err error
		var match bool
		var matchEscaped bool

		for _, field := range req.Header[key] {
			match, err = regexp.MatchString(value[0], field)
			// Some values may contain reserved regex params e.g. "()", try matching with these escaped.
			matchEscaped, err = regexp.MatchString(regexp.QuoteMeta(value[0]), field)

			if err != nil {
				return false, err
			}
			if match || matchEscaped {
				break
			}

		}

		if !match && !matchEscaped {
			return false, nil
		}
	}
	return true, nil
}

// MatchQueryParams matches the URL query params fields of the given request.
func MatchQueryParams(req *http.Request, ereq *Request) (bool, error) {
	for key, value := range ereq.URLStruct.Query() {
		var err error
		var match bool

		for _, field := range req.URL.Query()[key] {
			match, err = regexp.MatchString(value[0], field)
			if err != nil {
				return false, err
			}
			if match {
				break
			}
		}

		if !match {
			return false, nil
		}
	}
	return true, nil
}

// MatchPathParams matches the URL path parameters of the given request.
func MatchPathParams(req *http.Request, ereq *Request) (bool, error) {
	for key, value := range ereq.PathParams {
		var s string

		if err := parth.Sequent(req.URL.Path, key, &s); err != nil {
			return false, nil
		}

		if s != value {
			return false, nil
		}
	}
	return true, nil
}

// MatchBody tries to match the request body.
// TODO: not too smart now, needs several improvements.
func MatchBody(req *http.Request, ereq *Request) (bool, error) {
	// If match body is empty, just continue
	if req.Method == "HEAD" || len(ereq.BodyBuffer) == 0 {
		return true, nil
	}

	// Only can match certain MIME body types
	if !supportedType(req, ereq) {
		return false, nil
	}

	// Can only match certain compression schemes
	if !supportedCompressionScheme(req) {
		return false, nil
	}

	// Create a reader for the body depending on compression type
	bodyReader := req.Body
	if ereq.CompressionScheme != "" {
		if ereq.CompressionScheme != req.Header.Get("Content-Encoding") {
			return false, nil
		}
		compressedBodyReader, err := compressionReader(req.Body, ereq.CompressionScheme)
		if err != nil {
			return false, err
		}
		bodyReader = compressedBodyReader
	}

	// Read the whole request body
	body, err := ioutil.ReadAll(bodyReader)
	if err != nil {
		return false, err
	}

	// Restore body reader stream
	req.Body = createReadCloser(body)

	// If empty, ignore the match
	if len(body) == 0 && len(ereq.BodyBuffer) != 0 {
		return false, nil
	}

	// Match body by atomic string comparison
	bodyStr := castToString(body)
	matchStr := castToString(ereq.BodyBuffer)
	if bodyStr == matchStr {
		return true, nil
	}

	// Match request body by regexp
	match, _ := regexp.MatchString(matchStr, bodyStr)
	if match == true {
		return true, nil
	}

	// todo - add conditional do only perform the conversion of body bytes
	// representation of JSON to a map and then compare them for equality.

	// Check if the key + value pairs match
	var bodyMap map[string]interface{}
	var matchMap map[string]interface{}

	// Ensure that both byte bodies that that should be JSON can be converted to maps.
	umErr := json.Unmarshal(body, &bodyMap)
	umErr2 := json.Unmarshal(ereq.BodyBuffer, &matchMap)
	if umErr == nil && umErr2 == nil && reflect.DeepEqual(bodyMap, matchMap) {
		return true, nil
	}

	return false, nil
}

func supportedType(req *http.Request, ereq *Request) bool {
	mime := req.Header.Get("Content-Type")
	if mime == "" {
		return true
	}

	mimeToMatch := ereq.Header.Get("Content-Type")
	if mimeToMatch != "" {
		return mime == mimeToMatch
	}

	for _, kind := range BodyTypes {
		if match, _ := regexp.MatchString(kind, mime); match {
			return true
		}
	}
	return false
}

func supportedCompressionScheme(req *http.Request) bool {
	encoding := req.Header.Get("Content-Encoding")
	if encoding == "" {
		return true
	}

	for _, kind := range CompressionSchemes {
		if match, _ := regexp.MatchString(kind, encoding); match {
			return true
		}
	}
	return false
}

func castToString(buf []byte) string {
	str := string(buf)
	tail := len(str) - 1
	if str[tail] == EOL {
		str = str[:tail]
	}
	return str
}

func compressionReader(r io.ReadCloser, scheme string) (io.ReadCloser, error) {
	switch scheme {
	case "gzip":
		return gzip.NewReader(r)
	default:
		return r, nil
	}
}