package gocqlx

import (
	"bytes"
	"errors"
	"github.com/gocql/gocql"
	"strconv"
	"unicode"
)

type Queryx struct {
	*gocql.Query
	names []string
}

// Allow digits and letters in bind params;  additionally runes are
// checked against underscores, meaning that bind params can have be
// alphanumeric with underscores.  Mind the difference between unicode
// digits and numbers, where '5' is a digit but '五' is not.
var allowedBindRunes = []*unicode.RangeTable{unicode.Letter, unicode.Digit}

// CompileNamedQuery compiles a named query into an unbound query using the
// '?' bindvar and a list of names.
func CompileNamedQuery(qs []byte) (cql string, names []string, err error) {
	// guess number of names
	n := bytes.Count(qs, []byte(":"))
	if n == 0 {
		return "", nil, errors.New("expected a named query")
	}
	names = make([]string, 0, n)
	rebound := make([]byte, 0, len(qs))

	inName := false
	last := len(qs) - 1
	name := make([]byte, 0, 10)

	for i, b := range qs {
		// a ':' while we're in a name is an error
		if b == ':' {
			// if this is the second ':' in a '::' escape sequence, append a ':'
			if inName && i > 0 && qs[i-1] == ':' {
				rebound = append(rebound, ':')
				inName = false
				continue
			} else if inName {
				err = errors.New("unexpected `:` while reading named param at " + strconv.Itoa(i))
				return cql, names, err
			}
			inName = true
			name = []byte{}
			// if we're in a name, and this is an allowed character, continue
		} else if inName && (unicode.IsOneOf(allowedBindRunes, rune(b)) || b == '_' || b == '.') && i != last {
			// append the byte to the name if we are in a name and not on the last byte
			name = append(name, b)
			// if we're in a name and it's not an allowed character, the name is done
		} else if inName {
			inName = false
			// if this is the final byte of the string and it is part of the name, then
			// make sure to add it to the name
			if i == last && unicode.IsOneOf(allowedBindRunes, rune(b)) {
				name = append(name, b)
			}
			// add the string representation to the names list
			names = append(names, string(name))
			// add a proper bindvar for the bindType
			rebound = append(rebound, '?')
			// add this byte to string unless it was not part of the name
			if i != last {
				rebound = append(rebound, b)
			} else if !unicode.IsOneOf(allowedBindRunes, rune(b)) {
				rebound = append(rebound, b)
			}
		} else {
			// this is a normal byte and should just go onto the rebound query
			rebound = append(rebound, b)
		}
	}

	return string(rebound), names, err
}