package operator

import (
	"git.gophernest.net/azpect/TextEditor/internal/action"
	"git.gophernest.net/azpect/TextEditor/internal/core"
	tea "github.com/charmbracelet/bubbletea"
)

// ChangeOperator implements Operator (c, s, R) - changes (deletes and enters insert mode) text.
type ChangeOperator struct{}

// ChangeOperator.Operate: Changes text based on the current mode and motion type.
func (o ChangeOperator) Operate(m action.Model, start, end core.Position, mtype core.MotionType) tea.Cmd {
	switch m.Mode() {
	case core.VisualMode:
		changeCharSelection(m, start, end)
	case core.VisualLineMode:
		changeLineSelection(m, start, end)
	case core.VisualBlockMode:
		changeBlockSelection(m, start, end)
	case core.NormalMode:
		changeNormalMode(m, start, end, mtype)
	}
	return nil
}

// changeNormalMode: Changes text in normal mode based on motion type.
func changeNormalMode(m action.Model, start, end core.Position, mtype core.MotionType) {
	// Normalize so start is always before or equal to end
	if start.Line > end.Line || (start.Line == end.Line && start.Col > end.Col) {
		start, end = end, start
	}

	// Linewise motions (j, k, G, gg) always operate on whole lines
	if mtype == core.Linewise {
		changeLineSelection(m, start, end)
		return
	}

	// Charwise motions on same line
	if start.Line == end.Line {
		// No movement = nothing to change
		if start.Col == end.Col && mtype == core.CharwiseExclusive {
			m.SetMode(core.InsertMode)
			return
		}
		// Exclusive motion: end position not included, so back up one
		if mtype == core.CharwiseExclusive {
			end.Col--
		}
		if end.Col >= start.Col {
			changeCharSelection(m, start, end)
		} else {
			m.SetMode(core.InsertMode)
		}
		return
	}

	// Charwise motion spanning multiple lines
	changeCharSelection(m, start, end)
}

// changeCharSelection: Changes a character-wise selection and enters insert mode.
func changeCharSelection(m action.Model, start, end core.Position) {
	win := m.ActiveWindow()
	buf := m.ActiveBuffer()

	var deletedText string

	if start.Line == end.Line {
		line := buf.Line(start.Line)
		endCol := min(end.Col+1, len(line))
		deletedText = line[start.Col:endCol]
		buf.SetLine(start.Line, line[:start.Col]+line[endCol:])
	} else {
		startLine := buf.Line(start.Line)
		endLine := buf.Line(end.Line)

		// Extract deleted text
		deletedText = startLine[start.Col:] + "\n"
		for y := start.Line + 1; y < end.Line; y++ {
			deletedText += buf.Line(y) + "\n"
		}
		endCol := min(end.Col+1, len(endLine))
		deletedText += endLine[:endCol]

		prefix := startLine[:start.Col]
		suffix := ""
		if end.Col+1 < len(endLine) {
			suffix = endLine[end.Col+1:]
		}

		// Delete from end back to start to preserve indices
		for i := end.Line; i >= start.Line; i-- {
			buf.DeleteLine(i)
		}
		buf.InsertLine(start.Line, prefix+suffix)
	}

	win.SetCursorLine(start.Line)
	win.SetCursorCol(start.Col)
	m.SetMode(core.InsertMode)

	// Update register with deleted text
	m.UpdateDefaultRegister(core.CharwiseRegister, []string{deletedText})
}

// changeLineSelection: Changes entire lines and enters insert mode.
func changeLineSelection(m action.Model, start, end core.Position) {
	win := m.ActiveWindow()
	buf := m.ActiveBuffer()

	var lines []string

	for i := end.Line; i >= start.Line; i-- {
		lines = append([]string{buf.Line(i)}, lines...)
		buf.DeleteLine(i)
	}

	// Insert an empty line for editing
	insertY := min(start.Line, buf.LineCount())
	buf.InsertLine(insertY, "")

	win.SetCursorLine(insertY)
	win.SetCursorCol(0)
	m.SetMode(core.InsertMode)

	// Update registers
	m.UpdateDefaultRegister(core.LinewiseRegister, lines)
}

// changeBlockSelection: Changes a rectangular block selection and enters insert mode.
func changeBlockSelection(m action.Model, start, end core.Position) {
	win := m.ActiveWindow()
	buf := m.ActiveBuffer()

	startCol := min(start.Col, end.Col)
	endCol := max(start.Col, end.Col)

	for y := start.Line; y <= end.Line; y++ {
		line := buf.Line(y)
		if startCol >= len(line) {
			continue
		}
		ec := min(endCol+1, len(line))
		buf.SetLine(y, line[:startCol]+line[ec:])
	}

	win.SetCursorLine(start.Line)
	win.SetCursorCol(startCol)
	m.SetMode(core.InsertMode)
}

// Verify ChangeOperator implements DoublePresser
var _ action.DoublePresser = ChangeOperator{}

// ChangeOperator.DoublePress: Handles cc - changes Count entire lines.
func (o ChangeOperator) DoublePress(m action.Model, count int) tea.Cmd {
	win := m.ActiveWindow()
	buf := m.ActiveBuffer()

	startY := win.Cursor.Line

	// If we have a higher value than lines remaining, we can only run so many times
	opCount := min(count, buf.LineCount()-startY)

	var lines []string

	// Collect lines to delete (always delete at startY since lines shift up)
	for range opCount {
		lines = append(lines, buf.Line(startY))
		buf.DeleteLine(startY)
	}

	// Put deleted lines in register
	m.UpdateDefaultRegister(core.LinewiseRegister, lines)

	// Insert empty line at the original position for editing
	// If we deleted everything, startY might be past end, so clamp it
	insertY := min(startY, buf.LineCount())
	buf.InsertLine(insertY, "")

	// Position cursor on the new empty line
	win.SetCursorLine(insertY)
	win.SetCursorCol(0)
	m.SetMode(core.InsertMode)

	return nil
}