package cli

import (
	"strings"

	"github.com/charmbracelet/lipgloss"
	"github.com/charmbracelet/x/ansi"
)

// The frame every full-screen llmgw screen is drawn in: a title bar, a
// sidebar of steps or actions on the left, the content in a bordered panel on
// the right, the keys along the bottom — and a dialog over it all when one is
// open. One frame, so the setup and the console read as one program.
//
// Keyboard only: these run on serial consoles and IPMI as often as in a
// desktop terminal.

// navItem is one line of the sidebar.
type navItem struct {
	Label string
	// State is "done", "current", "todo" for steps; "" for menu entries,
	// where Current marks the one focused.
	State   string
	Current bool
	// Dim greys an entry that cannot be chosen now.
	Dim bool
	// Heading is a title between groups of entries, not an entry.
	Heading bool
}

type frame struct {
	Width, Height int
	Title         string // left of the title bar
	Where         string // right of the title bar: the machine
	NavTitle      string
	Nav           []navItem
	PanelTitle    string
	Body          string
	// Scroll is how many of the body's lines are scrolled off the top.
	Scroll int
	Keys   string
	// Dialog, when set, is drawn over the middle of the screen.
	Dialog      string
	DialogTitle string
}

var (
	fBar      = lipgloss.NewStyle().Bold(true).Foreground(lipgloss.AdaptiveColor{Light: "#FFFFFF", Dark: "#0B1B1B"}).Background(tuiAccent)
	fBorder   = lipgloss.NewStyle().Border(lipgloss.RoundedBorder()).BorderForeground(tuiDim)
	fFocus    = lipgloss.NewStyle().Border(lipgloss.RoundedBorder()).BorderForeground(tuiAccent)
	fKeys     = lipgloss.NewStyle().Foreground(tuiDim)
	fSelected = lipgloss.NewStyle().Bold(true).Foreground(tuiAccent)
	fDialog   = lipgloss.NewStyle().Border(lipgloss.DoubleBorder()).BorderForeground(tuiAccent).Padding(1, 2)
)

const navWidth = 24

// render draws the whole screen, exactly Width by Height.
func (f frame) render() string {
	w, h := max(f.Width, 60), max(f.Height, 16)

	title := " " + f.Title
	right := f.Where + " "
	gap := max(1, w-ansi.StringWidth(title)-ansi.StringWidth(right))
	bar := fBar.Render(title + strings.Repeat(" ", gap) + right)

	// Panels fill what the bars leave: one line each above and below.
	ph := h - 2
	inner := ph - 2 // borders

	var navLines []string
	cur := 0
	for _, it := range f.Nav {
		mark := "  "
		label := it.Label
		if it.Heading {
			navLines = append(navLines, sDim.Render(label))
			continue
		}
		if it.Current || it.State == "current" {
			cur = len(navLines)
		}
		switch {
		case it.State == "done":
			mark = sOK.Render("✓ ")
		case it.State == "current":
			mark = fSelected.Render("› ")
			label = fSelected.Render(label)
		case it.Current:
			mark = fSelected.Render("› ")
			label = fSelected.Render(label)
		case it.Dim || it.State == "todo":
			label = sDim.Render(label)
		}
		navLines = append(navLines, truncateWidth(mark+label, navWidth-2))
	}
	// Taller than the screen: the part around the current entry, with a mark
	// at an edge that has more beyond it.
	if len(navLines) > inner {
		total := len(navLines)
		top := min(max(0, cur-inner/2), total-inner)
		navLines = append([]string{}, navLines[top:top+inner]...)
		if top > 0 {
			navLines[0] = sDim.Render("  ↑ more")
		}
		if top+inner < total {
			navLines[inner-1] = sDim.Render("  ↓ more")
		}
	}
	left := box(fBorder, f.NavTitle, strings.Join(navLines, "\n"), navWidth, inner)

	pw := w - navWidth - 2 - 2
	lines := strings.Split(strings.TrimRight(f.Body, "\n"), "\n")
	scroll := min(max(f.Scroll, 0), max(0, len(lines)-inner))
	visible := lines[scroll:]
	if len(visible) > inner {
		visible = visible[:inner]
		// Said in the last line, where it is seen.
		visible[inner-1] = sDim.Render("  ↓ more — PgDn")
	}
	for i := range visible {
		visible[i] = truncateWidth(visible[i], pw)
	}
	panelTitle := f.PanelTitle
	if scroll > 0 {
		panelTitle += " ↑"
	}
	main := box(fFocus, panelTitle, strings.Join(visible, "\n"), pw, inner)

	keys := fKeys.Render(" " + truncateWidth(f.Keys, w-2))
	screen := bar + "\n" + lipgloss.JoinHorizontal(lipgloss.Top, left, main) + "\n" + keys

	if f.Dialog != "" {
		dw := min(w-8, max(50, maxLineWidth(f.Dialog)+6))
		d := fDialog.Width(dw).Render(f.Dialog)
		if f.DialogTitle != "" {
			d = titled(d, f.DialogTitle)
		}
		screen = overlay(screen, d, w, h)
	}
	return screen
}

// box draws content in a border of the given inner size, with a title set
// into the top edge.
func box(style lipgloss.Style, title, content string, width, height int) string {
	b := style.Width(width).Height(height).Render(content)
	if title == "" {
		return b
	}
	return titled(b, title)
}

// titled sets " title " into a box's top border, after its corner.
func titled(b, title string) string {
	lines := strings.Split(b, "\n")
	if len(lines) == 0 {
		return b
	}
	top := lines[0]
	t := " " + title + " "
	tw := ansi.StringWidth(t)
	if ansi.StringWidth(top) < tw+4 {
		return b
	}
	lines[0] = ansi.Truncate(top, 2, "") + sTitle.Render(t) + ansi.TruncateLeft(top, 2+tw, "")
	return strings.Join(lines, "\n")
}

// overlay draws top over the middle of base, both w by h.
func overlay(base, top string, w, h int) string {
	bl := strings.Split(base, "\n")
	tl := strings.Split(top, "\n")
	tw := maxLineWidth(top)
	x := max(0, (w-tw)/2)
	y := max(0, (h-len(tl))/2)
	for i, l := range tl {
		row := y + i
		if row >= len(bl) {
			break
		}
		under := bl[row]
		left := ansi.Truncate(under, x, "")
		if pad := x - ansi.StringWidth(left); pad > 0 {
			left += strings.Repeat(" ", pad)
		}
		right := ansi.TruncateLeft(under, x+ansi.StringWidth(l), "")
		bl[row] = left + l + right
	}
	return strings.Join(bl, "\n")
}

func maxLineWidth(s string) int {
	n := 0
	for _, l := range strings.Split(s, "\n") {
		n = max(n, ansi.StringWidth(l))
	}
	return n
}

// truncateWidth cuts a line, colours and all, to w cells.
func truncateWidth(s string, w int) string {
	if ansi.StringWidth(s) <= w {
		return s
	}
	return ansi.Truncate(s, max(w-1, 0), "…")
}

// table draws rows under a header in columns as wide as they need, cut to
// width; the selected row is shown reversed when the panel has the focus.
func table(headers []string, rows [][]string, selected int, width int, focused bool) string {
	widths := make([]int, len(headers))
	for i, h := range headers {
		widths[i] = ansi.StringWidth(h)
	}
	for _, r := range rows {
		for i := range headers {
			if i < len(r) {
				widths[i] = min(max(widths[i], ansi.StringWidth(r[i])), 44)
			}
		}
	}
	line := func(cells []string) string {
		var b strings.Builder
		for i := range headers {
			c := ""
			if i < len(cells) {
				c = truncateWidth(cells[i], widths[i])
			}
			b.WriteString(c)
			if i < len(headers)-1 {
				b.WriteString(strings.Repeat(" ", widths[i]-ansi.StringWidth(c)+2))
			}
		}
		return truncateWidth(b.String(), width)
	}
	var b strings.Builder
	b.WriteString("  " + lipgloss.NewStyle().Bold(true).Foreground(tuiDim).Render(line(headers)) + "\n")
	for i, r := range rows {
		l := line(r)
		switch {
		case i == selected && focused:
			pad := max(0, width-ansi.StringWidth(ansi.Strip(l)))
			l = fBar.Render(ansi.Strip(l) + strings.Repeat(" ", pad))
		case i == selected:
			l = lipgloss.NewStyle().Bold(true).Render(l)
		}
		b.WriteString("  " + l + "\n")
	}
	if len(rows) == 0 {
		b.WriteString("  " + sDim.Render("nothing yet") + "\n")
	}
	return b.String()
}