package parser

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

// The primary building block of a TOML document is the key/value pair.
func startKeyValuePair(p *parsekit.P) {
	switch {
	case p.On(whitespace + carriageReturn + newline).Skip():
		p.Repeat()
	case p.On(hash).Stay():
		p.RouteTo(startComment).ThenReturnHere()
	case p.On(startOfKey).RouteTo(startKey):
	default:
		p.RouteTo(endOfFile)
	}
}

// A key may be either bare, quoted or dotted.
func startKey(p *parsekit.P) {
	switch {
	case p.On(bareKeyChars).RouteTo(startBareKey):
	default:
		p.UnexpectedInput("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 startBareKey(p *parsekit.P) {
	p.AcceptConsecutive(bareKeyChars) // TODO make a plan for adding this to After()
	p.EmitLiteral(ItemKey)
	p.RouteTo(endOfKeyOrDot)
}

// Dotted keys are a sequence of bare or quoted keys joined with a dot.
// This allows for grouping similar properties together:
func endOfKeyOrDot(p *parsekit.P) {
	// Whitespace around dot-separated parts is ignored, however,
	// best practice is to not use any extraneous whitespace.
	p.SkipConsecutive(whitespace)
	if p.On(dot).Accept() {
		p.SkipConsecutive(whitespace)
		p.EmitLiteral(ItemKeyDot)
		p.RouteTo(startKey)
	} else {
		p.RouteTo(startKeyAssignment)
	}
}

// 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 startKeyAssignment(p *parsekit.P) {
	p.SkipConsecutive(whitespace)
	if p.On(equal).Accept() {
		p.EmitLiteral(ItemAssignment)
		p.SkipConsecutive(whitespace)
		p.RouteTo(startValue)
	} else {
		p.UnexpectedInput("a value assignment")
	}
}