package prompt

import "strings"

const (
	leftPrefix       = " "
	leftSuffix       = " "
	rightPrefix      = " "
	rightSuffix      = " "
	leftMargin       = len(leftPrefix + leftSuffix)
	rightMargin      = len(rightPrefix + rightSuffix)
	completionMargin = leftMargin + rightMargin
)

type Render struct {
	out    ConsoleWriter
	prefix string
	title  string
	row    uint16
	col    uint16
	// colors
	prefixTextColor              Color
	prefixBGColor                Color
	inputTextColor               Color
	inputBGColor                 Color
	previewSuggestionTextColor   Color
	previewSuggestionBGColor     Color
	suggestionTextColor          Color
	suggestionBGColor            Color
	selectedSuggestionTextColor  Color
	selectedSuggestionBGColor    Color
	descriptionTextColor         Color
	descriptionBGColor           Color
	selectedDescriptionTextColor Color
	selectedDescriptionBGColor   Color
}

func (r *Render) Setup() {
	if r.title != "" {
		r.out.SetTitle(r.title)
		r.out.Flush()
	}
}

func (r *Render) renderPrefix() {
	r.out.SetColor(r.prefixTextColor, r.prefixBGColor, false)
	r.out.WriteStr(r.prefix)
	r.out.SetColor(DefaultColor, DefaultColor, false)
}

func (r *Render) TearDown() {
	r.out.ClearTitle()
	r.out.EraseDown()
	r.out.Flush()
}

func (r *Render) prepareArea(lines int) {
	for i := 0; i < lines; i++ {
		r.out.ScrollDown()
	}
	for i := 0; i < lines; i++ {
		r.out.ScrollUp()
	}
	return
}

func (r *Render) UpdateWinSize(ws *WinSize) {
	r.row = ws.Row
	r.col = ws.Col
	return
}

func (r *Render) renderWindowTooSmall() {
	r.out.CursorGoTo(0, 0)
	r.out.EraseScreen()
	r.out.SetColor(DarkRed, White, false)
	r.out.WriteStr("Your console window is too small...")
	r.out.Flush()
	return
}

func (r *Render) renderCompletion(buf *Buffer, completions []Suggest, max uint16, selected int) {
	if max > r.row {
		max = r.row
	}

	if l := len(completions); l == 0 {
		return
	} else if l > int(max) {
		completions = completions[:max]
	}

	formatted, width := formatCompletions(
		completions,
		int(r.col)-len(r.prefix),
	)
	l := len(formatted)
	r.prepareArea(l)

	d := (len(r.prefix) + len(buf.Document().TextBeforeCursor())) % int(r.col)
	if d == 0 { // the cursor is on right end.
		r.out.CursorBackward(width)
	} else if d+width > int(r.col) {
		r.out.CursorBackward(d + width - int(r.col))
	}

	r.out.SetColor(White, Cyan, false)
	for i := 0; i < l; i++ {
		r.out.CursorDown(1)
		if i == selected {
			r.out.SetColor(r.selectedSuggestionTextColor, r.selectedSuggestionBGColor, true)
		} else {
			r.out.SetColor(r.suggestionTextColor, r.suggestionBGColor, false)
		}
		r.out.WriteStr(formatted[i].Text)

		if i == selected {
			r.out.SetColor(r.selectedDescriptionTextColor, r.selectedDescriptionBGColor, false)
		} else {
			r.out.SetColor(r.descriptionTextColor, r.descriptionBGColor, false)
		}
		r.out.WriteStr(formatted[i].Description)
		r.out.CursorBackward(width)
	}
	if d == 0 { // the cursor is on right end.
		// DON'T CURSOR DOWN HERE. Because the line doesn't erase properly.
		r.out.CursorForward(width + 1)
	} else if d+width > int(r.col) {
		r.out.CursorForward(d + width - int(r.col))
	}

	r.out.CursorUp(l)
	r.out.SetColor(DefaultColor, DefaultColor, false)
	return
}

func (r *Render) Render(buffer *Buffer, completions []Suggest, maxCompletions uint16, selected int) {
	// Erasing
	r.out.CursorBackward(int(r.col) + len(buffer.Text()) + len(r.prefix))
	r.out.EraseDown()

	// prepare area
	line := buffer.Text()
	h := ((len(r.prefix) + len(line)) / int(r.col)) + 1 + int(maxCompletions)
	if h > int(r.row) || completionMargin > int(r.col) {
		r.renderWindowTooSmall()
		return
	}

	// Rendering
	r.renderPrefix()

	r.out.SetColor(r.inputTextColor, r.inputBGColor, false)
	r.out.WriteStr(line)
	r.out.SetColor(DefaultColor, DefaultColor, false)
	r.out.CursorBackward(len(line) - buffer.CursorPosition)
	r.renderCompletion(buffer, completions, maxCompletions, selected)
	if selected != -1 {
		c := completions[selected]
		r.out.CursorBackward(len([]rune(buffer.Document().GetWordBeforeCursor())))
		r.out.SetColor(r.previewSuggestionTextColor, r.previewSuggestionBGColor, false)
		r.out.WriteStr(c.Text)
		r.out.SetColor(DefaultColor, DefaultColor, false)
	}
	r.out.Flush()
}

func (r *Render) BreakLine(buffer *Buffer) {
	// CR
	r.out.CursorBackward(int(r.col) + len(buffer.Text()) + len(r.prefix))
	// Erasing and Render
	r.out.EraseDown()
	r.renderPrefix()
	r.out.SetColor(r.inputTextColor, r.inputBGColor, false)
	r.out.WriteStr(buffer.Document().Text + "\n")
	r.out.SetColor(DefaultColor, DefaultColor, false)
	r.out.Flush()
}

func formatCompletions(completions []Suggest, max int) (new []Suggest, width int) {
	num := len(completions)
	new = make([]Suggest, num)
	leftWidth := 0
	rightWidth := 0

	for i := 0; i < num; i++ {
		if leftWidth < len([]rune(completions[i].Text)) {
			leftWidth = len([]rune(completions[i].Text))
		}
		if rightWidth < len([]rune(completions[i].Description)) {
			rightWidth = len([]rune(completions[i].Description))
		}
	}

	if diff := max - completionMargin - leftWidth - rightWidth; diff < 0 {
		if rightWidth > diff {
			rightWidth += diff
		} else if rightWidth+rightMargin > -diff {
			leftWidth += rightWidth + rightMargin + diff
			rightWidth = 0
		}
	}
	if rightWidth == 0 {
		width = leftWidth + leftMargin
	} else {
		width = leftWidth + leftMargin + rightWidth + rightMargin
	}

	for i := 0; i < num; i++ {
		var newText string
		var newDescription string
		if l := len(completions[i].Text); l > leftWidth {
			newText = leftPrefix + completions[i].Text[:leftWidth-len("...")] + "..." + leftSuffix
		} else if l < width {
			spaces := strings.Repeat(" ", leftWidth-len([]rune(completions[i].Text)))
			newText = leftPrefix + completions[i].Text + spaces + leftSuffix
		} else {
			newText = leftPrefix + completions[i].Text + leftSuffix
		}

		if rightWidth == 0 {
			newDescription = ""
		} else if l := len(completions[i].Description); l > rightWidth {
			newDescription = rightPrefix + completions[i].Description[:rightWidth-len("...")] + "..." + rightSuffix
		} else if l < width {
			spaces := strings.Repeat(" ", rightWidth-len([]rune(completions[i].Description)))
			newDescription = rightPrefix + completions[i].Description + spaces + rightSuffix
		} else {
			newDescription = rightPrefix + completions[i].Description + rightSuffix
		}
		new[i] = Suggest{Text: newText, Description: newDescription}
	}
	return
}