// ⚡️ Fiber is an Express inspired web framework written in Go with ☕️
// 📄 Github Repository: https://github.com/gofiber/fiber
// 📌 API Documentation: https://docs.gofiber.io
// ⚠️ This path parser was inspired by ucarion/urlpath (MIT License).
// 💖 Maintained and modified for Fiber by @renewerner87

package fiber

import (
	"regexp"
	"strconv"
	"strings"
	"time"
	"unicode"

	"github.com/gofiber/fiber/v2/utils"
	"github.com/google/uuid"
)

// routeParser holds the path segments and param names
type routeParser struct {
	segs          []*routeSegment // the parsed segments of the route
	params        []string        // that parameter names the parsed route
	wildCardCount int             // number of wildcard parameters, used internally to give the wildcard parameter its number
	plusCount     int             // number of plus parameters, used internally to give the plus parameter its number
}

// paramsSeg holds the segment metadata
type routeSegment struct {
	// const information
	Const string // constant part of the route
	// parameter information
	IsParam     bool   // Truth value that indicates whether it is a parameter or a constant part
	ParamName   string // name of the parameter for access to it, for wildcards and plus parameters access iterators starting with 1 are added
	ComparePart string // search part to find the end of the parameter
	PartCount   int    // how often is the search part contained in the non-param segments? -> necessary for greedy search
	IsGreedy    bool   // indicates whether the parameter is greedy or not, is used with wildcard and plus
	IsOptional  bool   // indicates whether the parameter is optional or not
	// common information
	IsLast           bool          // shows if the segment is the last one for the route
	HasOptionalSlash bool          // segment has the possibility of an optional slash
	Constraints      []*Constraint // Constraint type if segment is a parameter, if not it will be set to noConstraint by default
	Length           int           // length of the parameter for segment, when its 0 then the length is undetermined
	// future TODO: add support for optional groups "/abc(/def)?"
}

// different special routing signs
const (
	wildcardParam                byte = '*'  // indicates an optional greedy parameter
	plusParam                    byte = '+'  // indicates a required greedy parameter
	optionalParam                byte = '?'  // concludes a parameter by name and makes it optional
	paramStarterChar             byte = ':'  // start character for a parameter with name
	slashDelimiter               byte = '/'  // separator for the route, unlike the other delimiters this character at the end can be optional
	escapeChar                   byte = '\\' // escape character
	paramConstraintStart         byte = '<'  // start of type constraint for a parameter
	paramConstraintEnd           byte = '>'  // end of type constraint for a parameter
	paramConstraintSeparator     byte = ';'  // separator of type constraints for a parameter
	paramConstraintDataStart     byte = '('  // start of data of type constraint for a parameter
	paramConstraintDataEnd       byte = ')'  // end of data of type constraint for a parameter
	paramConstraintDataSeparator byte = ','  // separator of datas of type constraint for a parameter
)

// TypeConstraint parameter constraint types
type TypeConstraint int16

type Constraint struct {
	ID            TypeConstraint
	RegexCompiler *regexp.Regexp
	Data          []string
}

const (
	noConstraint TypeConstraint = iota + 1
	intConstraint
	boolConstraint
	floatConstraint
	alphaConstraint
	datetimeConstraint
	guidConstraint
	minLenConstraint
	maxLenConstraint
	lenConstraint
	betweenLenConstraint
	minConstraint
	maxConstraint
	rangeConstraint
	regexConstraint
)

// list of possible parameter and segment delimiter
var (
	// slash has a special role, unlike the other parameters it must not be interpreted as a parameter
	routeDelimiter = []byte{slashDelimiter, '-', '.'}
	// list of greedy parameters
	greedyParameters = []byte{wildcardParam, plusParam}
	// list of chars for the parameter recognizing
	parameterStartChars = []byte{wildcardParam, plusParam, paramStarterChar}
	// list of chars of delimiters and the starting parameter name char
	parameterDelimiterChars = append([]byte{paramStarterChar, escapeChar}, routeDelimiter...)
	// list of chars to find the end of a parameter
	parameterEndChars = append([]byte{optionalParam}, parameterDelimiterChars...)
	// list of parameter constraint start
	parameterConstraintStartChars = []byte{paramConstraintStart}
	// list of parameter constraint end
	parameterConstraintEndChars = []byte{paramConstraintEnd}
	// list of parameter separator
	parameterConstraintSeparatorChars = []byte{paramConstraintSeparator}
	// list of parameter constraint data start
	parameterConstraintDataStartChars = []byte{paramConstraintDataStart}
	// list of parameter constraint data end
	parameterConstraintDataEndChars = []byte{paramConstraintDataEnd}
	// list of parameter constraint data separator
	parameterConstraintDataSeparatorChars = []byte{paramConstraintDataSeparator}
)

// RoutePatternMatch checks if a given path matches a Fiber route pattern.
func RoutePatternMatch(path, pattern string, cfg ...Config) bool {
	// See logic in (*Route).match and (*App).register
	var ctxParams [maxParams]string

	config := Config{}
	if len(cfg) > 0 {
		config = cfg[0]
	}

	if path == "" {
		path = "/"
	}

	// Cannot have an empty pattern
	if pattern == "" {
		pattern = "/"
	}
	// Pattern always start with a '/'
	if pattern[0] != '/' {
		pattern = "/" + pattern
	}

	patternPretty := pattern

	// Case-sensitive routing, all to lowercase
	if !config.CaseSensitive {
		patternPretty = utils.ToLower(patternPretty)
		path = utils.ToLower(path)
	}
	// Strict routing, remove trailing slashes
	if !config.StrictRouting && len(patternPretty) > 1 {
		patternPretty = utils.TrimRight(patternPretty, '/')
	}

	parser := parseRoute(patternPretty)

	if patternPretty == "/" && path == "/" {
		return true
		// '*' wildcard matches any path
	} else if patternPretty == "/*" {
		return true
	}

	// Does this route have parameters
	if len(parser.params) > 0 {
		if match := parser.getMatch(path, path, &ctxParams, false); match {
			return true
		}
	}
	// Check for a simple match
	patternPretty = RemoveEscapeChar(patternPretty)
	if len(patternPretty) == len(path) && patternPretty == path {
		return true
	}
	// No match
	return false
}

// parseRoute analyzes the route and divides it into segments for constant areas and parameters,
// this information is needed later when assigning the requests to the declared routes
func parseRoute(pattern string) routeParser {
	parser := routeParser{}

	part := ""
	for len(pattern) > 0 {
		nextParamPosition := findNextParamPosition(pattern)
		// handle the parameter part
		if nextParamPosition == 0 {
			processedPart, seg := parser.analyseParameterPart(pattern)
			parser.params, parser.segs, part = append(parser.params, seg.ParamName), append(parser.segs, seg), processedPart
		} else {
			processedPart, seg := parser.analyseConstantPart(pattern, nextParamPosition)
			parser.segs, part = append(parser.segs, seg), processedPart
		}

		// reduce the pattern by the processed parts
		if len(part) == len(pattern) {
			break
		}
		pattern = pattern[len(part):]
	}
	// mark last segment
	if len(parser.segs) > 0 {
		parser.segs[len(parser.segs)-1].IsLast = true
	}
	parser.segs = addParameterMetaInfo(parser.segs)

	return parser
}

// addParameterMetaInfo add important meta information to the parameter segments
// to simplify the search for the end of the parameter
func addParameterMetaInfo(segs []*routeSegment) []*routeSegment {
	var comparePart string
	segLen := len(segs)
	// loop from end to begin
	for i := segLen - 1; i >= 0; i-- {
		// set the compare part for the parameter
		if segs[i].IsParam {
			// important for finding the end of the parameter
			segs[i].ComparePart = RemoveEscapeChar(comparePart)
		} else {
			comparePart = segs[i].Const
			if len(comparePart) > 1 {
				comparePart = utils.TrimRight(comparePart, slashDelimiter)
			}
		}
	}

	// loop from begin to end
	for i := 0; i < segLen; i++ {
		// check how often the compare part is in the following const parts
		if segs[i].IsParam {
			// check if parameter segments are directly after each other and if one of them is greedy
			// in case the next parameter or the current parameter is not a wildcard it's not greedy, we only want one character
			if segLen > i+1 && !segs[i].IsGreedy && segs[i+1].IsParam && !segs[i+1].IsGreedy {
				segs[i].Length = 1
			}
			if segs[i].ComparePart == "" {
				continue
			}
			for j := i + 1; j <= len(segs)-1; j++ {
				if !segs[j].IsParam {
					// count is important for the greedy match
					segs[i].PartCount += strings.Count(segs[j].Const, segs[i].ComparePart)
				}
			}
			// check if the end of the segment is a optional slash and then if the segement is optional or the last one
		} else if segs[i].Const[len(segs[i].Const)-1] == slashDelimiter && (segs[i].IsLast || (segLen > i+1 && segs[i+1].IsOptional)) {
			segs[i].HasOptionalSlash = true
		}
	}

	return segs
}

// findNextParamPosition search for the next possible parameter start position
func findNextParamPosition(pattern string) int {
	nextParamPosition := findNextNonEscapedCharsetPosition(pattern, parameterStartChars)
	if nextParamPosition != -1 && len(pattern) > nextParamPosition && pattern[nextParamPosition] != wildcardParam {
		// search for parameter characters for the found parameter start,
		// if there are more, move the parameter start to the last parameter char
		for found := findNextNonEscapedCharsetPosition(pattern[nextParamPosition+1:], parameterStartChars); found == 0; {
			nextParamPosition++
			if len(pattern) > nextParamPosition {
				break
			}
		}
	}

	return nextParamPosition
}

// analyseConstantPart find the end of the constant part and create the route segment
func (*routeParser) analyseConstantPart(pattern string, nextParamPosition int) (string, *routeSegment) {
	// handle the constant part
	processedPart := pattern
	if nextParamPosition != -1 {
		// remove the constant part until the parameter
		processedPart = pattern[:nextParamPosition]
	}
	constPart := RemoveEscapeChar(processedPart)
	return processedPart, &routeSegment{
		Const:  constPart,
		Length: len(constPart),
	}
}

// analyseParameterPart find the parameter end and create the route segment
func (routeParser *routeParser) analyseParameterPart(pattern string) (string, *routeSegment) {
	isWildCard := pattern[0] == wildcardParam
	isPlusParam := pattern[0] == plusParam

	var parameterEndPosition int
	if strings.ContainsRune(pattern, rune(paramConstraintStart)) && strings.ContainsRune(pattern, rune(paramConstraintEnd)) {
		parameterEndPosition = findNextCharsetPositionConstraint(pattern[1:], parameterEndChars)
	} else {
		parameterEndPosition = findNextNonEscapedCharsetPosition(pattern[1:], parameterEndChars)
	}

	parameterConstraintStart := -1
	parameterConstraintEnd := -1
	// handle wildcard end
	switch {
	case isWildCard, isPlusParam:
		parameterEndPosition = 0
	case parameterEndPosition == -1:
		parameterEndPosition = len(pattern) - 1
	case !isInCharset(pattern[parameterEndPosition+1], parameterDelimiterChars):
		parameterEndPosition++
	}

	// find constraint part if exists in the parameter part and remove it
	if parameterEndPosition > 0 {
		parameterConstraintStart = findNextNonEscapedCharsetPosition(pattern[0:parameterEndPosition], parameterConstraintStartChars)
		parameterConstraintEnd = findLastCharsetPosition(pattern[0:parameterEndPosition+1], parameterConstraintEndChars)
	}

	// cut params part
	processedPart := pattern[0 : parameterEndPosition+1]
	paramName := RemoveEscapeChar(GetTrimmedParam(processedPart))

	// Check has constraint
	var constraints []*Constraint

	if hasConstraint := parameterConstraintStart != -1 && parameterConstraintEnd != -1; hasConstraint {
		constraintString := pattern[parameterConstraintStart+1 : parameterConstraintEnd]
		userConstraints := splitNonEscaped(constraintString, string(parameterConstraintSeparatorChars))
		constraints = make([]*Constraint, 0, len(userConstraints))

		for _, c := range userConstraints {
			start := findNextNonEscapedCharsetPosition(c, parameterConstraintDataStartChars)
			end := findLastCharsetPosition(c, parameterConstraintDataEndChars)

			// Assign constraint
			if start != -1 && end != -1 {
				constraint := &Constraint{
					ID: getParamConstraintType(c[:start]),
				}

				// remove escapes from data
				if constraint.ID != regexConstraint {
					constraint.Data = splitNonEscaped(c[start+1:end], string(parameterConstraintDataSeparatorChars))
					if len(constraint.Data) == 1 {
						constraint.Data[0] = RemoveEscapeChar(constraint.Data[0])
					} else if len(constraint.Data) == 2 { // This is fine, we simply expect two parts
						constraint.Data[0] = RemoveEscapeChar(constraint.Data[0])
						constraint.Data[1] = RemoveEscapeChar(constraint.Data[1])
					}
				}

				// Precompile regex if has regex constraint
				if constraint.ID == regexConstraint {
					constraint.Data = []string{c[start+1 : end]}
					constraint.RegexCompiler = regexp.MustCompile(constraint.Data[0])
				}

				constraints = append(constraints, constraint)
			} else {
				constraints = append(constraints, &Constraint{
					ID:   getParamConstraintType(c),
					Data: []string{},
				})
			}
		}

		paramName = RemoveEscapeChar(GetTrimmedParam(pattern[0:parameterConstraintStart]))
	}

	// add access iterator to wildcard and plus
	if isWildCard {
		routeParser.wildCardCount++
		paramName += strconv.Itoa(routeParser.wildCardCount)
	} else if isPlusParam {
		routeParser.plusCount++
		paramName += strconv.Itoa(routeParser.plusCount)
	}

	segment := &routeSegment{
		ParamName:  paramName,
		IsParam:    true,
		IsOptional: isWildCard || pattern[parameterEndPosition] == optionalParam,
		IsGreedy:   isWildCard || isPlusParam,
	}

	if len(constraints) > 0 {
		segment.Constraints = constraints
	}

	return processedPart, segment
}

// isInCharset check is the given character in the charset list
func isInCharset(searchChar byte, charset []byte) bool {
	for _, char := range charset {
		if char == searchChar {
			return true
		}
	}
	return false
}

// findNextCharsetPosition search the next char position from the charset
func findNextCharsetPosition(search string, charset []byte) int {
	nextPosition := -1
	for _, char := range charset {
		if pos := strings.IndexByte(search, char); pos != -1 && (pos < nextPosition || nextPosition == -1) {
			nextPosition = pos
		}
	}

	return nextPosition
}

// findNextCharsetPosition search the last char position from the charset
func findLastCharsetPosition(search string, charset []byte) int {
	lastPosition := -1
	for _, char := range charset {
		if pos := strings.LastIndexByte(search, char); pos != -1 && (pos < lastPosition || lastPosition == -1) {
			lastPosition = pos
		}
	}

	return lastPosition
}

// findNextCharsetPositionConstraint search the next char position from the charset
// unlike findNextCharsetPosition, it takes care of constraint start-end chars to parse route pattern
func findNextCharsetPositionConstraint(search string, charset []byte) int {
	constraintStart := findNextNonEscapedCharsetPosition(search, parameterConstraintStartChars)
	constraintEnd := findNextNonEscapedCharsetPosition(search, parameterConstraintEndChars)
	nextPosition := -1

	for _, char := range charset {
		pos := strings.IndexByte(search, char)

		if pos != -1 && (pos < nextPosition || nextPosition == -1) {
			if (pos > constraintStart && pos > constraintEnd) || (pos < constraintStart && pos < constraintEnd) {
				nextPosition = pos
			}
		}
	}

	return nextPosition
}

// findNextNonEscapedCharsetPosition search the next char position from the charset and skip the escaped characters
func findNextNonEscapedCharsetPosition(search string, charset []byte) int {
	pos := findNextCharsetPosition(search, charset)
	for pos > 0 && search[pos-1] == escapeChar {
		if len(search) == pos+1 {
			// escaped character is at the end
			return -1
		}
		nextPossiblePos := findNextCharsetPosition(search[pos+1:], charset)
		if nextPossiblePos == -1 {
			return -1
		}
		// the previous character is taken into consideration
		pos = nextPossiblePos + pos + 1
	}

	return pos
}

// splitNonEscaped slices s into all substrings separated by sep and returns a slice of the substrings between those separators
// This function also takes a care of escape char when splitting.
func splitNonEscaped(s, sep string) []string {
	var result []string
	i := findNextNonEscapedCharsetPosition(s, []byte(sep))

	for i > -1 {
		result = append(result, s[:i])
		s = s[i+len(sep):]
		i = findNextNonEscapedCharsetPosition(s, []byte(sep))
	}

	return append(result, s)
}

// getMatch parses the passed url and tries to match it against the route segments and determine the parameter positions
func (routeParser *routeParser) getMatch(detectionPath, path string, params *[maxParams]string, partialCheck bool) bool { //nolint: revive // Accepting a bool param is fine here
	var i, paramsIterator, partLen int
	for _, segment := range routeParser.segs {
		partLen = len(detectionPath)
		// check const segment
		if !segment.IsParam {
			i = segment.Length
			// is optional part or the const part must match with the given string
			// check if the end of the segment is an optional slash
			if segment.HasOptionalSlash && partLen == i-1 && detectionPath == segment.Const[:i-1] {
				i--
			} else if !(i <= partLen && detectionPath[:i] == segment.Const) {
				return false
			}
		} else {
			// determine parameter length
			i = findParamLen(detectionPath, segment)
			if !segment.IsOptional && i == 0 {
				return false
			}
			// take over the params positions
			params[paramsIterator] = path[:i]

			if !(segment.IsOptional && i == 0) {
				// check constraint
				for _, c := range segment.Constraints {
					if matched := c.CheckConstraint(params[paramsIterator]); !matched {
						return false
					}
				}
			}

			paramsIterator++
		}

		// reduce founded part from the string
		if partLen > 0 {
			detectionPath, path = detectionPath[i:], path[i:]
		}
	}
	if detectionPath != "" && !partialCheck {
		return false
	}

	return true
}

// findParamLen for the expressjs wildcard behavior (right to left greedy)
// look at the other segments and take what is left for the wildcard from right to left
func findParamLen(s string, segment *routeSegment) int {
	if segment.IsLast {
		return findParamLenForLastSegment(s, segment)
	}

	if segment.Length != 0 && len(s) >= segment.Length {
		return segment.Length
	} else if segment.IsGreedy {
		// Search the parameters until the next constant part
		// special logic for greedy params
		searchCount := strings.Count(s, segment.ComparePart)
		if searchCount > 1 {
			return findGreedyParamLen(s, searchCount, segment)
		}
	}

	if len(segment.ComparePart) == 1 {
		if constPosition := strings.IndexByte(s, segment.ComparePart[0]); constPosition != -1 {
			return constPosition
		}
	} else if constPosition := strings.Index(s, segment.ComparePart); constPosition != -1 {
		// if the compare part was found, but contains a slash although this part is not greedy, then it must not match
		// example: /api/:param/fixedEnd -> path: /api/123/456/fixedEnd = no match , /api/123/fixedEnd = match
		if !segment.IsGreedy && strings.IndexByte(s[:constPosition], slashDelimiter) != -1 {
			return 0
		}
		return constPosition
	}

	return len(s)
}

// findParamLenForLastSegment get the length of the parameter if it is the last segment
func findParamLenForLastSegment(s string, seg *routeSegment) int {
	if !seg.IsGreedy {
		if i := strings.IndexByte(s, slashDelimiter); i != -1 {
			return i
		}
	}

	return len(s)
}

// findGreedyParamLen get the length of the parameter for greedy segments from right to left
func findGreedyParamLen(s string, searchCount int, segment *routeSegment) int {
	// check all from right to left segments
	for i := segment.PartCount; i > 0 && searchCount > 0; i-- {
		searchCount--
		if constPosition := strings.LastIndex(s, segment.ComparePart); constPosition != -1 {
			s = s[:constPosition]
		} else {
			break
		}
	}

	return len(s)
}

// GetTrimmedParam trims the ':' & '?' from a string
func GetTrimmedParam(param string) string {
	start := 0
	end := len(param)

	if end == 0 || param[start] != paramStarterChar { // is not a param
		return param
	}
	start++
	if param[end-1] == optionalParam { // is ?
		end--
	}

	return param[start:end]
}

// RemoveEscapeChar remove escape characters
func RemoveEscapeChar(word string) string {
	if strings.IndexByte(word, escapeChar) != -1 {
		return strings.ReplaceAll(word, string(escapeChar), "")
	}
	return word
}

func getParamConstraintType(constraintPart string) TypeConstraint {
	switch constraintPart {
	case ConstraintInt:
		return intConstraint
	case ConstraintBool:
		return boolConstraint
	case ConstraintFloat:
		return floatConstraint
	case ConstraintAlpha:
		return alphaConstraint
	case ConstraintGuid:
		return guidConstraint
	case ConstraintMinLen, ConstraintMinLenLower:
		return minLenConstraint
	case ConstraintMaxLen, ConstraintMaxLenLower:
		return maxLenConstraint
	case ConstraintLen:
		return lenConstraint
	case ConstraintBetweenLen, ConstraintBetweenLenLower:
		return betweenLenConstraint
	case ConstraintMin:
		return minConstraint
	case ConstraintMax:
		return maxConstraint
	case ConstraintRange:
		return rangeConstraint
	case ConstraintDatetime:
		return datetimeConstraint
	case ConstraintRegex:
		return regexConstraint
	default:
		return noConstraint
	}
}

//nolint:errcheck // TODO: Properly check _all_ errors in here, log them & immediately return
func (c *Constraint) CheckConstraint(param string) bool {
	var err error
	var num int

	// check data exists
	needOneData := []TypeConstraint{minLenConstraint, maxLenConstraint, lenConstraint, minConstraint, maxConstraint, datetimeConstraint, regexConstraint}
	needTwoData := []TypeConstraint{betweenLenConstraint, rangeConstraint}

	for _, data := range needOneData {
		if c.ID == data && len(c.Data) == 0 {
			return false
		}
	}

	for _, data := range needTwoData {
		if c.ID == data && len(c.Data) < 2 {
			return false
		}
	}

	// check constraints
	switch c.ID {
	case noConstraint:
		// Nothing to check
	case intConstraint:
		_, err = strconv.Atoi(param)
	case boolConstraint:
		_, err = strconv.ParseBool(param)
	case floatConstraint:
		_, err = strconv.ParseFloat(param, 32)
	case alphaConstraint:
		for _, r := range param {
			if !unicode.IsLetter(r) {
				return false
			}
		}
	case guidConstraint:
		_, err = uuid.Parse(param)
	case minLenConstraint:
		data, _ := strconv.Atoi(c.Data[0])

		if len(param) < data {
			return false
		}
	case maxLenConstraint:
		data, _ := strconv.Atoi(c.Data[0])

		if len(param) > data {
			return false
		}
	case lenConstraint:
		data, _ := strconv.Atoi(c.Data[0])

		if len(param) != data {
			return false
		}
	case betweenLenConstraint:
		data, _ := strconv.Atoi(c.Data[0])
		data2, _ := strconv.Atoi(c.Data[1])
		length := len(param)
		if length < data || length > data2 {
			return false
		}
	case minConstraint:
		data, _ := strconv.Atoi(c.Data[0])
		num, err = strconv.Atoi(param)

		if num < data {
			return false
		}
	case maxConstraint:
		data, _ := strconv.Atoi(c.Data[0])
		num, err = strconv.Atoi(param)

		if num > data {
			return false
		}
	case rangeConstraint:
		data, _ := strconv.Atoi(c.Data[0])
		data2, _ := strconv.Atoi(c.Data[1])
		num, err = strconv.Atoi(param)

		if num < data || num > data2 {
			return false
		}
	case datetimeConstraint:
		_, err = time.Parse(c.Data[0], param)
	case regexConstraint:
		if match := c.RegexCompiler.MatchString(param); !match {
			return false
		}
	}

	return err == nil
}