package editor

import (
	"fmt"
	"strconv"
	"strings"

	"git.gophernest.net/azpect/TextEditor/internal/core"
	"git.gophernest.net/azpect/TextEditor/internal/syntax"
	"git.gophernest.net/azpect/TextEditor/internal/theme"
	"github.com/charmbracelet/lipgloss"
)

// Model.View: Renders the complete editor view including buffer content, line
// numbers, status bar, and command line.
func (m Model) View() string {
	win := m.ActiveWindow()

	// NOTES:
	// One single command line across entire viewport
	// Each window has its own line numbers and gutter
	// Each window has its own status bar and mode

	_, t := m.Theme()
	options := win.Options

	// Adjust gutter to fit line len
	maxLineLen := len(strconv.Itoa(win.Buffer.LineCount()))
	options.GutterSize = max(options.GutterSize, maxLineLen+2)

	// Draw window
	view := viewWindow(win, t, options, m.Mode(), m.Syntax())

	// Command bar is separate
	cmdBar := drawCommandBar(m, t)
	view += cmdBar

	// Handle command output, draw on top
	// TODO: This is not idea, but it works for now
	cmd := m.CommandOutput()
	if cmd != nil && cmd.IsActive() && !cmd.Inline && cmd.Height() > 0 {
		view = overlayCommandOutputWindow(view, cmd, t, m.termWidth, m.termHeight)
	}

	return view
}

// viewWindow: Renders a single window's content including line numbers and buffer text.
// Each window has its own line numbers, gutter, and viewport dimensions.
func viewWindow(w *core.Window, t theme.EditorTheme, options core.WinOptions, mode core.Mode, sx syntax.Engine) string {
	buf := w.Buffer
	var view strings.Builder
	if sx != nil {
		sx.PrepareBuffer(buf, t)
	}

	// Compute window size (y)
	start := w.ScrollY
	end := w.ScrollY + w.ViewportHeight()

	// Draw buffer lines
	for lineNum := start; lineNum < end; lineNum++ {
		if lineNum < buf.LineCount() {
			styleMap := make([]lipgloss.Style, len([]rune(buf.Line(lineNum))))
			if sx != nil {
				styleMap = sx.LineStyleMap(buf, lineNum, t)
			}
			line := drawLine(w, t, options, mode, buf.Line(lineNum), lineNum, styleMap)
			view.WriteString(line)
		} else {
			view.WriteString(strings.Repeat(t.Background.Render(" "), w.Width))
		}
		view.WriteRune('\n')
	}

	// Draw status line
	statusBar := drawStatusBar(w, mode, t)
	view.WriteString(statusBar + "\n")

	return view.String()
}

// drawLine: Renders a single line with syntax highlighting, cursor, and visual selection.
// Handles gutter, cursor rendering, and visual mode highlighting.
func drawLine(w *core.Window, t theme.EditorTheme, options core.WinOptions, mode core.Mode, line string, lineNumber int, styleMap []lipgloss.Style) string {
	var view strings.Builder
	runes := []rune(line)

	// Draw gutter first
	gutter := drawGutter(w, t, options, lineNumber)
	view.WriteString(gutter)

	// Now draw the line content
	for col := 0; col <= len(runes); col++ {
		// Current char is cursor
		if col == w.Cursor.Col && lineNumber == w.Cursor.Line {
			if col < len(runes) {
				cur := t.Cursor(mode, styleMap[col])
				view.WriteString(cur.Render(string(runes[col])))
			} else {
				view.WriteString(t.DefaultCursor(mode).Render(" "))
			}

			// Not cursor, but not end
		} else if col < len(runes) {
			s := styleMap[col]
			if mode.IsVisualMode() && posInsideSelection(w, mode, col, lineNumber) {
				vis := t.VisualHighlightWithTextColor(s)
				view.WriteString(vis.Render(string(runes[col])))
			} else {
				view.WriteString(s.Render(string(runes[col])))
			}
			// Allow highlight on blank lines or chars
		} else if mode.IsVisualMode() && posInsideSelection(w, mode, col, lineNumber) {
			view.WriteString(t.VisualHightlight.Render(" "))
		}
	}

	// Pad remainder of line to window width with background color
	dif := w.Width - lipgloss.Width(view.String())
	if dif > 0 {
		view.WriteString(strings.Repeat(t.Background.Render(" "), dif))
	}

	return view.String()
}

// drawGutter: Renders the line number gutter with support for both absolute and
// relative line numbers, highlighting the current line differently.
func drawGutter(w *core.Window, t theme.EditorTheme, options core.WinOptions, curLine int) string {
	if !(options.Number || options.RelativeNumber) {
		return ""
	}

	// Required vars
	var (
		view        strings.Builder
		gutSize     int  = options.GutterSize - 1 // -1 is for padding
		currentLine bool = curLine == w.Cursor.Line
		lineNumber  int

		gutter         string
		gutterStyle    = t.Gutter.Default
		gutterStyleCur = t.Gutter.CurrentLine
	)

	// If we have relative setting, set the numbers relatively
	if options.RelativeNumber {
		if curLine > w.Cursor.Line {
			lineNumber = curLine - w.Cursor.Line
		}

		if curLine < w.Cursor.Line {
			lineNumber = w.Cursor.Line - curLine
		}
	}

	// If we have number setting AND not relative setting OR we are on current line, use current line number
	if (options.Number && !options.RelativeNumber) || (options.Number && currentLine) {
		lineNumber = curLine + 1
	}

	// Draw the gutter
	gutter = fmt.Sprintf("%*d ", gutSize, lineNumber)
	if currentLine {
		view.WriteString(gutterStyleCur.Render(gutter))
	} else {
		view.WriteString(gutterStyle.Render(gutter))
	}

	return view.String()
}

// drawStatusBar: Renders the status bar with mode and cursor position,
// padding the middle with spaces to fill the terminal width.
func drawStatusBar(w *core.Window, mode core.Mode, t theme.EditorTheme) string {
	left := leftBar(w, mode, t)
	right := rightBar(w, mode, t)

	diff := w.Width - (lipgloss.Width(left) + lipgloss.Width(right))

	// This happens when the terminal spawns
	if diff <= 0 {
		return ""
	}

	middle := strings.Repeat(t.Background.Render(" "), diff)
	return left + middle + right
}

// leftBar: Returns the left side of the status bar showing the current mode.
func leftBar(w *core.Window, mode core.Mode, t theme.EditorTheme) string {
	buf := w.Buffer

	var flags []string
	if buf.Modified {
		flags = append(flags, "!")
	}
	if buf.ReadOnly {
		flags = append(flags, "x")
	}

	var flagStr string
	if len(flags) > 0 {
		flagStr = "(" + strings.Join(flags, "") + ")"
	}

	bar := fmt.Sprintf(" %s  %s %s", mode.ToString(), buf.Filename, flagStr)
	return t.Line.Render(bar)
}

// rightBar: Returns the right side of the status bar showing cursor position
// and selection count in visual mode.
func rightBar(w *core.Window, mode core.Mode, t theme.EditorTheme) (bar string) {
	if mode.IsVisualMode() {
		lineCount := max(w.Anchor.Line, w.Cursor.Line) - min(w.Anchor.Line, w.Cursor.Line) + 1
		bar = fmt.Sprintf("%d:%d  <%d>", w.Cursor.Line+1, w.Cursor.Col+1, lineCount)
	} else {
		bar = fmt.Sprintf("%d:%d ", w.Cursor.Line+1, w.Cursor.Col+1)
	}
	buf := w.Buffer
	bar = t.Line.Render(fmt.Sprintf("%s %s", buf.Filetype, bar))
	return
}

// drawCommandBar: Renders the command line showing command input, errors, or
// output depending on the current mode and state.
func drawCommandBar(m Model, t theme.EditorTheme) string {

	// Compute left bar (command side)
	var leftBar string
	if m.Mode() == core.CommandMode {
		leftBar = t.Line.Render(":")
		cmd := []rune(m.Command())
		cur := m.CommandCursor()
		for i, r := range cmd {
			if i == cur {
				leftBar += t.DefaultCursor(m.Mode()).Render(string(r))
			} else {
				leftBar += t.Line.Render(string(r))
			}
		}
		// Cursor at end of command
		if cur >= len(cmd) {
			leftBar += t.DefaultCursor(m.Mode()).Render(" ")
		}
		// bar = fmt.Sprintf("%s  %d", bar, cur)
	} else if out := m.CommandOutput(); out != nil && len(out.Lines) > 0 && out.Inline {
		// TODO: This is not perfect, temporary
		text := strings.Join(out.Lines, " ")
		if out.IsError {
			leftBar = t.CommandLine.Error.Render(text)
		} else {
			leftBar = t.Line.Render(text)
		}
	} else if strings.TrimSpace(m.Command()) != "" {
		content := fmt.Sprintf(":%s", m.Command())
		leftBar = t.Line.Render(content)
	}

	// Compute right bar

	var rightBar string
	if len(m.input.Pending()) > 0 {
		width := 10 // Size of the block to display
		content := fmt.Sprintf("%-*s", width, m.input.Pending())
		rightBar = t.Line.Render(content)
	}

	dif := m.termWidth - (lipgloss.Width(leftBar) + lipgloss.Width(rightBar))

	bar := leftBar + strings.Repeat(t.Background.Render(" "), max(0, dif)) + rightBar
	return bar
}

// posInsideSelection: Returns true if the given position is inside the current
// visual selection, handling all three visual modes differently.
func posInsideSelection(w *core.Window, mode core.Mode, col, line int) bool {
	switch mode {
	case core.VisualLineMode:
		startY := min(w.Anchor.Line, w.Cursor.Line)
		endY := max(w.Anchor.Line, w.Cursor.Line)
		return line >= startY && line <= endY

	case core.VisualMode:
		ax := w.Anchor.Col
		ay := w.Anchor.Line

		cx := w.Cursor.Col
		cy := w.Cursor.Line

		// Normalize so start is always before end in document order
		var startX, startY, endX, endY int
		if ay < cy || (ay == cy && ax <= cx) {
			startX, startY = ax, ay
			endX, endY = cx, cy
		} else {
			startX, startY = cx, cy
			endX, endY = ax, ay
		}

		// Position is inside if it falls within [start, end] inclusive
		afterStart := line > startY || (line == startY && col >= startX)
		beforeEnd := line < endY || (line == endY && col <= endX)
		return afterStart && beforeEnd

	case core.VisualBlockMode:
		startX := min(w.Anchor.Col, w.Cursor.Col)
		startY := min(w.Anchor.Line, w.Cursor.Line)
		endX := max(w.Anchor.Col, w.Cursor.Col)
		endY := max(w.Anchor.Line, w.Cursor.Line)

		return col >= startX && col <= endX &&
			line >= startY && line <= endY

	default:
		return false
	}
}

// overlayCommandOutputWindow: Draw the overlay of the command output window. This will override
// (overlay) the displayed content, so it should be used only when needed.
func overlayCommandOutputWindow(view string, cmd *core.CommandOutput, t theme.EditorTheme, termWidth int, termHeight int) string {
	// Safety check
	if cmd == nil {
		return view
	}

	// Split the lines and get the last few
	lines := strings.Split(view, "\n")

	// Build the overlay
	var overlay []string
	overlay = append(overlay, t.CommandLine.OutputBorder.Render(strings.Repeat(" ", termWidth)))

	if strings.TrimSpace(cmd.Title) != "" {
		title := t.Line.Render(cmd.Title)
		overlay = append(overlay, title)
	}
	viewLines := cmd.Viewport(termHeight)
	for _, l := range viewLines {
		content := t.Line.Render(strings.ReplaceAll(l, "\n", "\\n"))
		overlay = append(overlay, content)
	}
	msg := core.CommandOutputExitMessage
	if len(cmd.Lines) > len(cmd.Viewport(termHeight)) {
		msg += ". " + core.CommandOutputScrollMessage
	}
	overlay = append(overlay, t.CommandLine.ContinueMessage.Render(msg))

	// NOTE: strings.Split on "\n" is safe as long as no style uses .Width()/.Height()/.Padding()/.Margin(),
	// which would cause Lipgloss to embed newlines internally and corrupt the line count.
	// If block-level styles are ever added, this approach must be replaced.

	// Add background color to end of each line
	for i, l := range overlay {
		dif := termWidth - lipgloss.Width(l)
		overlay[i] += t.Background.Render(strings.Repeat(" ", dif))
	}

	// Remove 'h' lines from back of view and append overlay
	h := len(overlay)
	final := lines[:max(0, len(lines)-h)]
	final = append(final, overlay...)

	return strings.Join(final, "\n")
}