package app

import (
	"fmt"
	"os"
	"strings"
	"sync"
)

// toastKind classifies a toast for styling and for migrating the
// pre-existing flashError / flashTransient / notifyAttention call
// sites onto the new stack.
type toastKind int

const (
	toastInfo toastKind = iota
	toastError
	toastAttention
)

// toast is one entry in the host-level notification stack. Toasts
// persist until the user dismisses them with Ctrl-N or the
// "Clear notifications" palette command — there's no auto-expiry.
type toast struct {
	id   uint64
	kind toastKind
	text string
}

// toastStackCap caps how many toasts can be visible at once.
// Older entries drop off the bottom when a new push would exceed it.
const toastStackCap = 5

// toastBoxMaxWidth bounds the rendered box width so a wide pane
// doesn't produce huge toasts. Boxes shrink below this when the pane
// is narrow.
const toastBoxMaxWidth = 50

// toastBoxMinWidth is the floor below which we refuse to render —
// any narrower and there's not enough room for borders + content.
const toastBoxMinWidth = 20

// toastStack owns the ordered list of live toasts. Oldest at
// index 0, newest (visually topmost) at the end. The stack's own
// mutex is intentionally separate from uiState.mu so push / dismiss
// can be called from any goroutine without participating in the
// host's bigger lock-ordering rules.
type toastStack struct {
	mu    sync.Mutex
	items []toast
	next  uint64
}

func (s *toastStack) push(kind toastKind, text string) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.next++
	s.items = append(s.items, toast{id: s.next, kind: kind, text: text})
	if len(s.items) > toastStackCap {
		s.items = s.items[len(s.items)-toastStackCap:]
	}
}

// dismissTop pops the most recent toast (the one rendered at the
// top of the stack). Returns true if something was removed so
// callers can decide whether to repaint.
func (s *toastStack) dismissTop() bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	if len(s.items) == 0 {
		return false
	}
	s.items = s.items[:len(s.items)-1]
	return true
}

func (s *toastStack) clear() bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	if len(s.items) == 0 {
		return false
	}
	s.items = s.items[:0]
	return true
}

func (s *toastStack) snapshot() []toast {
	s.mu.Lock()
	defer s.mu.Unlock()
	if len(s.items) == 0 {
		return nil
	}
	out := make([]toast, len(s.items))
	copy(out, s.items)
	return out
}

func (s *toastStack) length() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return len(s.items)
}

// notifyToast is the single entry point that the former flash
// helpers now delegate to. It pushes onto the stack and triggers a
// repaint of the focused surface so the new toast appears
// immediately; the repaint path also re-renders the stack on top.
func (st *uiState) notifyToast(kind toastKind, text string) {
	st.toasts.push(kind, text)
	st.refreshToastSurface()
}

// refreshToastSurface re-renders whatever surface the toasts are
// drawn over (focused child, focused pad, or the empty-state
// canvas). Each of those paths calls renderToasts at the end, so
// the toast layer is always reapplied on top of a freshly-drawn
// pane. Centralised so push / dismiss / clear share one code path.
func (st *uiState) refreshToastSurface() {
	st.mu.Lock()
	focusedPad := st.focusedPad
	focusedID := st.focusedID
	palOpen := st.palette != nil
	st.mu.Unlock()
	if palOpen {
		// Palette owns the whole screen while it's open; toasts will
		// repaint via closePalette's restore path.
		return
	}
	switch {
	case focusedPad != "":
		st.repaintFocusedPad()
	case focusedID != "":
		st.repaintFocused()
	default:
		st.renderEmptyState()
	}
}

// renderToasts draws the toast stack over the top-right of the
// focused pane. Called from repaintFocused / repaintFocusedPad /
// renderEmptyState after they finish so toasts always sit on top of
// freshly-redrawn pane content. Safe to call when the stack is
// empty (no-op).
func (st *uiState) renderToasts() {
	items := st.toasts.snapshot()
	if len(items) == 0 {
		return
	}
	st.mu.Lock()
	palOpen := st.palette != nil
	st.mu.Unlock()
	if palOpen {
		return
	}
	layout := st.layoutSnapshot()
	paneCols := int(layout.childCols())
	paneRows := int(layout.childRows())
	if paneCols < toastBoxMinWidth+2 || paneRows < 3 {
		return
	}
	boxWidth := toastBoxMaxWidth
	if max := paneCols - 4; max < boxWidth {
		boxWidth = max
	}
	if boxWidth < toastBoxMinWidth {
		return
	}
	contentWidth := boxWidth - 4 // 2 border cells + 2 inner padding

	var b strings.Builder
	b.WriteString("\x1b7\x1b[?25l")

	row := int(layout.mainTop) + 1
	col := int(layout.mainLeft) + paneCols - boxWidth - 1
	if col < int(layout.mainLeft) {
		col = int(layout.mainLeft)
	}

	// Render newest first (visually on top), iterating items in
	// reverse so the most recent push lands at the smallest row.
	for idx := len(items) - 1; idx >= 0; idx-- {
		t := items[idx]
		isTopmost := idx == len(items)-1
		hintLine := ""
		if isTopmost && len(items) > 1 {
			hintLine = fmt.Sprintf("Ctrl-N · %d more", len(items)-1)
		}
		height := 3
		if hintLine != "" {
			height++
		}
		// Stop if we'd run off the bottom of the pane.
		if row+height > int(layout.mainTop)+paneRows {
			break
		}
		border := toastBorderStyle(t.kind)

		// Top border.
		moveTo(&b, row, col)
		b.WriteString(border)
		b.WriteString("╭")
		b.WriteString(strings.Repeat("─", boxWidth-2))
		b.WriteString("╮")
		b.WriteString(styleReset)
		row++

		// Content row.
		moveTo(&b, row, col)
		b.WriteString(border)
		b.WriteString("│")
		b.WriteString(styleReset)
		b.WriteString(" ")
		b.WriteString(toastIcon(t.kind))
		body := t.text
		bodyRoom := contentWidth - 2 // icon + space
		if visibleLen(body) > bodyRoom {
			body = clipRunes(body, bodyRoom-1) + "…"
		}
		b.WriteString(body)
		b.WriteString(strings.Repeat(" ", max(0, bodyRoom-visibleLen(body))))
		b.WriteString(" ")
		b.WriteString(border)
		b.WriteString("│")
		b.WriteString(styleReset)
		row++

		// Hint row (topmost only, when stack has more than one).
		if hintLine != "" {
			if visibleLen(hintLine) > contentWidth {
				hintLine = clipRunes(hintLine, contentWidth-1) + "…"
			}
			moveTo(&b, row, col)
			b.WriteString(border)
			b.WriteString("│")
			b.WriteString(styleReset)
			b.WriteString(" ")
			b.WriteString(styleHint)
			b.WriteString(hintLine)
			b.WriteString(styleReset)
			b.WriteString(strings.Repeat(" ", max(0, contentWidth-visibleLen(hintLine))))
			b.WriteString(" ")
			b.WriteString(border)
			b.WriteString("│")
			b.WriteString(styleReset)
			row++
		}

		// Bottom border.
		moveTo(&b, row, col)
		b.WriteString(border)
		b.WriteString("╰")
		b.WriteString(strings.Repeat("─", boxWidth-2))
		b.WriteString("╯")
		b.WriteString(styleReset)
		row++

		// 1-row gap between stacked toasts.
		row++
	}

	b.WriteString("\x1b[?25h\x1b8")

	st.outMu.Lock()
	defer st.outMu.Unlock()
	_, _ = os.Stdout.WriteString(b.String())
}

func toastBorderStyle(kind toastKind) string {
	switch kind {
	case toastError:
		return styleError
	case toastAttention:
		return styleAccent
	default:
		return styleBorder
	}
}

func toastIcon(kind toastKind) string {
	switch kind {
	case toastError:
		return styleError + "✗ " + styleReset
	case toastAttention:
		return styleAccent + "! " + styleReset
	default:
		return styleHint + "• " + styleReset
	}
}