package parser

import (
	"fmt"
	"strings"
)

// Build builds an URI scheme from a pattern string
func Build(s string) (*Scheme, error){

	/* (1) Manage '/' at the start */
	if len(s) < 1 || s[0] != '/' {
		return nil, fmt.Errorf("URI must begin with '/'")
	}

	/* (2) Split by '/' */
	parts := strings.Split(s, "/")

	/* (3) Max exceeded */
	if len(parts)-2 > maxMatch {
		for i, p := range parts {
			fmt.Printf("%d: '%s'\n", i, p);
		}
		return nil, fmt.Errorf("URI must not exceed %d slash-separated components, got %d", maxMatch, len(parts))
	}

	/* (4) Build for each part */
	sch, err := buildScheme(parts)
	if err != nil {
		return nil, err
	}

	/* (5) Optimise structure */
	opti, err := sch.optimise()
	if err != nil {
		return nil, err
	}

	return &opti, nil

}


// Match returns if the given URI is matched by the scheme
func (s Scheme) Match(str string) bool {

	/* (1) Nothing -> match all */
	if len(s) == 0 { return true }

	/* (2) Init variables */
	wc := make(Scheme, 0, maxMatch) // conrains wildcards
	clr := str                     // contains cleared input string
	minOff := 0                     // minimum offset

	/* (3) Iterate over strings */
	for _, m := range s {

		ls := len(m.pat)

		// if not string -> ignore
		if ls == 0 {
			wc = append(wc, m)
			continue
		}

		// get offset if contained, else -1
		off := strings.Index(clr, m.pat)
		if off < 0 { return false }

		// if invalid offset range -> fail
		if off < minOff { return false }

		// check if trailing '/'
		slash := 0
		if off+ls < len(clr) && clr[off+ls] == '/' {
			slash = 1
		}

		// exclude this string (+trailing slash if set)
		// fmt.Printf("remove: '%s'\n", clr[off:off+ls+slash])
		beg, end := clr[:off], clr[off+ls+slash:]
		clr = fmt.Sprintf("%s//%s", beg, end)
		// fmt.Printf("clr: '%s'\n", clr)

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

	}

	/* (4) If no wildcard -> match */
	if len(wc) == 0 {
		return true
	}

	// flush wildcard buffers
	for _, w := range wc { w.buf = nil }

	/* (5) Break the clear string apart */
	matches := strings.Split(clr, "//")[1:]

	// fail if missing matches
	if len(matches) < len(wc) {
		return false
	}

	nwc := 0
	for _, m := range matches {

		// ignore empty
		if len(m) == 0 { continue }

		// no matcher for this match
		if nwc >= len(wc){ return false }

		// split by '/'
		parts := strings.Split(m, "/")

		// if required and missing -> does not match
		if wc[nwc].req && len(parts) < 1 {
			return false
		}

		// if not multi but multi -> does not match
		if !wc[nwc].mul && len(parts) > 1 {
			return false
		}

		// store into wilcard matcher
		wc[nwc].buf = parts

		// increment wildcard count
		nwc++

	}


	return true
}


// GetMatch returns the indexed match (excluding string matchers)
func (s Scheme) GetMatch(n uint8) ([]string, error) {

	/* (1) Index out of range */
	if n > uint8(len(s)) {
		return nil, fmt.Errorf("Index out of range")
	}

	/* (2) Iterate to find index (exclude strings) */
	ni := -1
	for i, l := 0, len(s) ; i < l ; i++ {

		// ignore strings
		if len(s[i].pat) > 0 { continue }

		// increment match counter : ni
		ni++

		// if expected index -> return matches
		if uint8(ni) == n {
			return s[i].buf, nil
		}

	}

	/* (3) If nothing found -> return empty set */
	return nil, fmt.Errorf("Index out of range (max: %d)", ni)

}