package rql

import (
	"github.com/alecthomas/participle/v2"
	"github.com/alecthomas/participle/v2/lexer"
)

var (
	rqlLexer = lexer.MustSimple([]lexer.SimpleRule{
		{Name: "whitespace", Pattern: `\s+`},
		{Name: "String", Pattern: `"[^"]*"`},
		{Name: "Ident", Pattern: `[a-zA-Z_][a-zA-Z_0-9]*`},
		{Name: "Punct", Pattern: `[-[!@#$%^&*()+_={};':",.<>?/]|]`},
	})

	rqlParser = participle.MustBuild[Query](
		participle.Lexer(rqlLexer),
		participle.Unquote("String"),
		participle.UseLookahead(2),
	)
)

func Parse(query string) (*Query, error) {
	return rqlParser.ParseString("", query)
}

type Operator string

type Values struct {
	Single *string  `parser:"@String"`
	List   []string `parser:"| ( '[' @String (',' @String)* ']' )"`
}

type Predicate struct {
	Key      string   `parser:"@Ident '.'"`
	Operator Operator `parser:"@('eq'|'lt'|'lte'|'gt'|'gte'|'like'|'in')"`
	Values   Values   `parser:"'=' @@"`
}

type Query struct {
	Predicates []*Predicate `parser:"@@*"`
}