const EOF = byte(0xff)

type BlockReader interface {
	Reader
	// Reset resets current state and sets new segments to the reader.
	Reset(segment *Segments)
}

type FindClosureOptions struct {
	// CodeSpan is a flag for the FindClosure. If this is set to true,
	// FindClosure ignores closers in codespans.
	CodeSpan bool

	// Nesting is a flag for the FindClosure. If this is set to true,
	// FindClosure allows nesting.
	Nesting bool

	// Newline is a flag for the FindClosure. If this is set to true,
	// FindClosure searches for a closer over multiple lines.
	Newline bool

	// Advance is a flag for the FindClosure. If this is set to true,
	// FindClosure advances pointers when closer is found.
	Advance bool
}

type Reader interface {
	io.RuneReader

	// Source returns a source of the reader.
	Source() []byte

	// ResetPosition resets positions.
	ResetPosition()

	// Peek returns a byte at current position without advancing the internal pointer.
	Peek() byte

	// PeekLine returns the current line without advancing the internal pointer.
	PeekLine() ([]byte, Segment)

	// PrecendingCharacter returns a character just before current internal pointer.
	PrecendingCharacter() rune

	// Value returns a value of the given segment.
	Value(Segment) []byte

	// LineOffset returns a distance from the line head to current position.
	LineOffset() int

	// Position returns current line number and position.
	Position() (int, Segment)

	// SetPosition sets current line number and position.
	SetPosition(int, Segment)

	// SetPadding sets padding to the reader.
	SetPadding(int)

	// Advance advances the internal pointer.
	Advance(int)

	// AdvanceAndSetPadding advances the internal pointer and add padding to the
	// reader.
	AdvanceAndSetPadding(int, int)

	// AdvanceLine advances the internal pointer to the next line head.
	AdvanceLine()

	// SkipSpaces skips space characters and returns a non-blank line.
	// If it reaches EOF, returns false.
	SkipSpaces() (Segment, int, bool)

	// SkipSpaces skips blank lines and returns a non-blank line.
	// If it reaches EOF, returns false.
	SkipBlankLines() (Segment, int, bool)

	// Match performs regular expression matching to current line.
	Match(reg *regexp.Regexp) bool

	// Match performs regular expression searching to current line.
	FindSubMatch(reg *regexp.Regexp) [][]byte

	// FindClosure finds corresponding closure.
	FindClosure(opener, closer byte, options FindClosureOptions) (*Segments, bool)
}

type Segment struct {
	// Start is a start position of the segment.
	Start int

	// Stop is a stop position of the segment.
	// This value should be excluded.
	Stop int

	// Padding is a padding length of the segment.
	Padding int

	// ForceNewline is true if the segment should be ended with a newline.
	// Some elements(i.e. CodeBlock, FencedCodeBlock) does not trim trailing
	// newlines. Spec defines that EOF is treated as a newline, so we need to
	// add a newline to the end of the segment if it is not empty.
	//
	// i.e.:
	//
	//     ```go
	//     const test = "test"
	//
	// This code does not close the code block and ends with EOF. In this case,
	// we need to add a newline to the end of the last line like `const test = "test"\n`.
	ForceNewline bool
}

type Segments struct {
	// contains filtered or unexported fields
}