package core

// RegisterType: Indicates how the register content should be interpreted when
// pasting. Charwise treats content as continuous text, linewise operates on
// complete lines, and blockwise represents rectangular selections.
type RegisterType int

const (
	CharwiseRegister RegisterType = iota
	LinewiseRegister
	BlockwiseRegister
)

func (r RegisterType) ToString() string {
	switch r {
	case CharwiseRegister:
		return "c"
	case LinewiseRegister:
		return "l"
	case BlockwiseRegister:
		return "b"
	}
	return "-"
}

// Register: Stores yanked or deleted text with metadata about how it should be
// pasted. The Type determines paste behavior and Content holds the text lines.
type Register struct {
	Type    RegisterType
	Content []string
}

// DefaultRegisters: Creates and initializes the complete set of vim-style
// registers. Returns a map containing special registers (", *, _, etc.),
// named registers (a-z), and numbered registers (0-9).
func DefaultRegisters() map[rune]Register {
	reg := make(map[rune]Register)

	addSpecialRegisters(reg)
	addNamedRegisters(reg)
	addNumberedRegisters(reg)

	return reg
}

// addNamedRegisters: Initializes the 26 named registers (a-z) used for explicit
// yank/delete operations. Users can target these with commands like "ayy or "ap.
func addNamedRegisters(reg map[rune]Register) {
	name := 'a'

	for name <= 'z' {
		reg[name] = emptyRegister()
		name++
	}
}

// addNumberedRegisters: Initializes the numbered registers (0-9) which form the
// delete history. Register 0 holds the most recent yank, and 1-9 hold previous
// deletes in chronological order.
func addNumberedRegisters(reg map[rune]Register) {
	name := '0'

	for name <= '9' {
		reg[name] = emptyRegister()
		name++
	}

}

// addSpecialRegisters: Initializes special-purpose registers with specific
// behaviors. Includes the unnamed register ("), black hole (_), clipboard (*),
// last insert (.), current filename (%), last command (:), and alternate file (#).
func addSpecialRegisters(reg map[rune]Register) {
	// Unnamed (default)
	reg['"'] = emptyRegister()

	// Black hole (readonly)
	reg['_'] = emptyRegister()

	// System clipboard
	reg['*'] = emptyRegister()

	// Small delete? Expression?

	// VIM: Last inserted text (readonly)
	// GIM: Content stored for the '.' operator (for debugging)
	reg['.'] = emptyRegister()

	// Current file name (readonly)
	reg['%'] = emptyRegister()

	// Last executed command (readonly)
	reg[':'] = emptyRegister()

	// Alternate (previous) file (readonly)
	reg['#'] = emptyRegister()
}

// emptyRegister: Creates a new register initialized with charwise type and empty
// content. Used as the default state for all registers during initialization.
func emptyRegister() Register {
	return Register{
		Type:    CharwiseRegister,
		Content: []string{},
	}
}