package parser

import (
	"fmt"
	"strings"
)

// buildScheme builds a 'basic' scheme
// from a pattern string
func buildScheme(ss []string) (Scheme, error) {

	/* (1) Build scheme */
	sch := make(Scheme, 0, maxMatch)

	for _, s := range ss {

		/* (2) ignore empty */
		if len(s) == 0 {
			continue
		}

		m := new(matcher)

		switch s {

		/* (3) Card: 0, N */
		case "**":
			m.req = false
			m.mul = true
			sch = append(sch, m)

		/* (4) Card: 1, N */
		case "..":
			m.req = true
			m.mul = true
			sch = append(sch, m)

		/* (5) Card: 0, 1 */
		case "*":
			m.req = false
			m.mul = false
			sch = append(sch, m)

		/* (6) Card: 1 */
		case ".":
			m.req = true
			m.mul = false
			sch = append(sch, m)

		/* (7) Card: 1, literal string */
		default:
			m.req = true
			m.mul = false
			m.pat = fmt.Sprintf("/%s", s)
			sch = append(sch, m)

		}

	}

	return sch, nil
}

// optimise optimised the scheme for further parsing
func (s Scheme) optimise() (Scheme, error) {

	/* (1) Nothing to do if only 1 element */
	if len(s) <= 1 {
		return s, nil
	}

	/* (2) Init reshifted scheme */
	rshift := make(Scheme, 0, maxMatch)
	rshift = append(rshift, s[0])

	/* (2) Iterate over matchers */
	for p, i, l := 0, 1, len(s); i < l; i++ {

		pre, cur := s[p], s[i]

		/* Merge: 2 following literals */
		if len(pre.pat) > 0 && len(cur.pat) > 0 {

			// merge strings into previous
			pre.pat = fmt.Sprintf("%s%s", pre.pat, cur.pat)

			// delete current
			s[i] = nil

		}

		// increment previous (only if current is not nul)
		if s[i] != nil {
			rshift = append(rshift, s[i])
			p = i
		}

	}

	return rshift, nil

}

// matchString checks the STRING matchers from an URI
// it returns a boolean : false when not matching, true eitherway
// it returns a cleared uri, without STRING data
func (s Scheme) matchString(uri string) (string, bool) {

	/* (1) Initialise variables */
	clr := uri  // contains cleared input string
	minOff := 0 // minimum offset

	/* (2) Iterate over strings */
	for _, m := range s {

		ls := len(m.pat)

		// {1} If not STRING matcher -> ignore //
		if ls == 0 {
			continue
		}

		// {2} Get offset in URI (else -1) //
		off := strings.Index(clr, m.pat)
		if off < 0 {
			return "", false
		}

		// {3} Fail on invalid offset range //
		if off < minOff {
			return "", false
		}

		// {4} Check for trailing '/' //
		hasSlash := 0
		if off+ls < len(clr) && clr[off+ls] == '/' {
			hasSlash = 1
		}

		// {5} Remove the current string (+trailing slash) from the URI //
		beg, end := clr[:off], clr[off+ls+hasSlash:]
		clr = fmt.Sprintf("%s\a/%s", beg, end) // separate matches by '\a' character

		// {6} Update offset range //
		minOff = len(beg) + 2 - 1 // +2 slash separators
		// -1 because strings begin with 1 slash already

	}

	/* (3) If exists, remove trailing '/' */
	if clr[len(clr)-1] == '/' {
		clr = clr[:len(clr)-1]
	}

	/* (4) If exists, remove trailing '\a' */
	if clr[len(clr)-1] == '\a' {
		clr = clr[:len(clr)-1]
	}

	return clr, true

}

// matchWildcards check the WILCARDS (non-string) matchers from
// a cleared URI. it returns if the string matches
// + it sets the matchers buffers for later extraction
func (s Scheme) matchWildcards(clear string) bool {

	/* (1) Extract wildcards (ref) */
	wildcards := make(Scheme, 0, maxMatch)

	for _, m := range s {
		if len(m.pat) == 0 {
			m.buf = nil // flush buffers
			wildcards = append(wildcards, m)
		}
	}

	/* (2) If no wildcards -> match */
	if len(wildcards) == 0 {
		return true
	}

	/* (3) Break uri by '\a' characters */
	matches := strings.Split(clear, "\a")[1:]

	/* (4) Iterate over matches */
	for n, match := range matches {

		// {1} If no more matcher //
		if n >= len(wildcards) {
			return false
		}

		// {2} Split by '/' //
		data := strings.Split(match, "/")[1:] // from index 1 because it begins with '/'

		// {3} If required and missing //
		if wildcards[n].req && len(data) < 1 {
			return false
		}

		// {4} If not multi but got multi //
		if !wildcards[n].mul && len(data) > 1 {
			return false
		}

		// {5} Store data into matcher //
		wildcards[n].buf = data

	}

	/* (5) Match */
	return true

}