package lexer

import "github.com/mmakaay/toml/parser"

// The primary building block of a TOML document is the key/value pair.
func stateKeyValuePair(l *parser.Parser) parser.StateFn {
	switch {
	case l.SkipConsecutive(whitespace + carriageReturn + newline):
		return stateKeyValuePair
	case l.Upcoming(hash):
		return l.ToChildState(stateCommentStart)
	case l.Upcoming(startOfKey):
		return stateKey
	default:
		return stateEndOfFile
	}
}

// A key may be either bare, quoted or dotted.
func stateKey(l *parser.Parser) parser.StateFn {
	if l.AcceptMatching(bareKeyChars) {
		return statebareKeyChars
	}
	return l.UnexpectedInputError("a valid key name")
}

// Bare keys may only contain ASCII letters, ASCII digits,
// underscores, and dashes (A-Za-z0-9_-). Note that bare
// keys are allowed to be composed of only ASCII digits,
// e.g. 1234, but are always interpreted as strings.
func statebareKeyChars(l *parser.Parser) parser.StateFn {
	l.AcceptConsecutive(bareKeyChars)
	l.EmitLiteral(ItemKey)
	return stateEndOfKeyOrKeyDot
}

// Dotted keys are a sequence of bare or quoted keys joined with a dot.
// This allows for grouping similar properties together:
func stateEndOfKeyOrKeyDot(l *parser.Parser) parser.StateFn {
	// Whitespace around dot-separated parts is ignored, however,
	// best practice is to not use any extraneous whitespace.
	l.SkipConsecutive(whitespace)
	if l.SkipMatching(dot) {
		l.Emit(ItemKeyDot, "")
		l.SkipConsecutive(whitespace)
		return stateKey
	}
	return stateKeyAssignment
}

// Keys are on the left of the equals sign and values are on the right.
// Whitespace is ignored around key names and values. The key, equals
// sign, and value must be on the same line (though some values can
// be broken over multiple lines).
func stateKeyAssignment(l *parser.Parser) parser.StateFn {
	l.SkipConsecutive(whitespace)
	if l.SkipMatching(equal) {
		l.Emit(ItemAssignment, "")
		l.SkipConsecutive(whitespace)
		return stateValue
	}
	return l.UnexpectedInputError("a value assignment")
}