module repl

import token as _ { Token, Tokenizer, TokenType }
import readline { read_line }

pub struct Repl {
pub:
	welcome_msg string = "Welcome to the REPL!"
}

/**
 * Caller owns returned memory.
 */
pub fn (r Repl) read(input string) ![]Token {
	mut tokens := []Token{
		len: 0,
		cap: 128,
		init: Token{0, .eof},
	}
	mut tokenizer := Tokenizer{input: input}

	for !tokenizer.end_of_input() {
		token := tokenizer.parse_all()!
		if token.tag == .eof { break }
		if token.tag == .newline {
			if tokens.len > 0 {
				break
			} else {
				continue // skip empty lines
			}
		}
		tokens << token
	}

	if tokens.len == 0 {
		return error('No input whatsoever')
	}

	return tokens
}

pub fn (r Repl) eval(ast []Token, input string) string {
	mut s := []string{len: 0, cap: 4096, init: ''}

	for token in ast {
	  s << ', '
		match token.tag {
			.eof { s << 'EOF' }
			.nil { s << 'nil' }
			.string { s << 'string' }
			.number { s << 'number' }
			.decimal { s << 'decimal' }
			.true { s << 'true' }
			.false { s << 'false' }
			.table_start { s << '{' }
			.table_end { s << '}' }
			.identifier { s << 'identifier' }
			.comma { s << ',' }
			.newline { s << '\n' }
			.equal { s << '=' }
			.dot { s << '.' }
			.angle_bracket_left { s << '[' }
			.angle_bracket_right { s << ']' }
			.keyword { s << 'keyword' }
			.operator, .operator_len2, .operator_len3{ s << 'operator' }
		}
	}

	if s.len == 0 {
		return 'No output'
	}

	return s.join(' ')
}

//fn (r Repl) print(t VuaType) {
pub fn (r Repl) print(t string) string {
	return t
}

pub fn (r Repl) loop() ! {
	for {
		input := read_line('vua>> ') or {
			println('\nGoodbye')
			break
		}
		if input.trim_space() == 'exit' {
			println('\nGoodbye')
			break
		}
		tokens := r.read(input.str())!
		expr := r.eval(tokens, input.str())
		output := r.print(expr)
		println(output)
	}
}