package ui

import (
	"strings"
	"time"

	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"

	"github.com/gmgauthier/gralculator/internal/calc"
)

// flashMsg and clearFlashMsg for timed visual feedback (140ms style from gostations).
type flashMsg struct{ which string }
type clearFlashMsg struct{ which string }

// tick returns a command that sends a flash clear after the given duration.
func tick(d time.Duration, which string) tea.Cmd {
	return tea.Tick(d, func(_ time.Time) tea.Msg {
		return clearFlashMsg{which: which}
	})
}

// App is the root Bubble Tea model.
// This is the focused rendering spike for the two-row display + single BASE keypad.
type App struct {
	engine *calc.Engine
	width  int
	height int

	// flash state for key actions and CERR
	flash     string // "base", "cerr", "op", "key", etc.
	cerrFlash bool

	// pressedKey tracks the last pressed keypad button for tactile "pressed" visual feedback
	pressedKey string
}

func NewApp() *App {
	return &App{
		engine: calc.NewEngine(),
	}
}

func (a *App) Init() tea.Cmd { return nil }

func (a *App) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		a.width = msg.Width
		a.height = msg.Height

	case flashMsg:
		a.flash = msg.which
		if msg.which == "cerr" {
			a.cerrFlash = true
		}
		return a, tick(140*time.Millisecond, msg.which)

	case clearFlashMsg:
		if msg.which == "cerr" {
			a.cerrFlash = false
		}
		if msg.which == "key" {
			a.pressedKey = ""
		}
		if a.flash == msg.which {
			a.flash = ""
		}
		return a, nil

	case tea.KeyMsg:
		switch msg.String() {
		case "q", "ctrl+c", "esc":
			return a, tea.Quit

		case "tab":
			if err := a.engine.CycleBase(); err == calc.ErrConversionNotPossible {
				a.flash = "cerr"
				a.cerrFlash = true
				return a, tick(600*time.Millisecond, "cerr")
			}
			a.flash = "base"
			// BASE is Tab-only now (no visual button in the grid).
			// The "base" flash will highlight the base label in the display row.
			return a, tick(140*time.Millisecond, "base")

		case "backspace":
			a.engine.ClearEntry()
			a.flash = "clear"
			a.pressedKey = "C"
			return a, tick(140*time.Millisecond, "key")

		case ".":
			a.engine.EnterDecimalPoint()
			a.pressedKey = "."
			return a, tick(140*time.Millisecond, "key")

		case "+", "-", "*", "/":
			a.engine.SetOperator(msg.String())
			a.flash = "op"
			a.pressedKey = msg.String()
			return a, tick(140*time.Millisecond, "key")

		case "m", "M": // MOD as immediate for convenience in spike
			a.engine.Mod()
			a.flash = "op"
			a.pressedKey = "MOD"
			return a, tick(140*time.Millisecond, "key")

		case "=", "enter":
			a.engine.Equals()
			a.flash = "eq"
			a.pressedKey = "="
			return a, tick(140*time.Millisecond, "key")

		case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9":
			a.engine.EnterDigit(rune(msg.String()[0]))
			a.pressedKey = msg.String()
			return a, tick(140*time.Millisecond, "key")

		// Tight-scope HEX entry: A-F (and a-f) only accepted while the base
		// indicator says HEX. We pass the rune (uppercased inside engine).
		// No visual buttons for A-F in this scope — keyboard only.
		case "a", "b", "c", "d", "e", "f", "A", "B", "C", "D", "E", "F":
			if a.engine.CurrentBase() == calc.BaseHEX {
				a.engine.EnterDigit(rune(msg.String()[0]))
				a.pressedKey = strings.ToUpper(msg.String())
				return a, tick(140*time.Millisecond, "key")
			}
			// In other bases: ignore (A-F reserved for future HEX entry)

		case "delete", "del": // All Clear
			a.engine.AllClear()
			a.flash = "clear"
			a.pressedKey = "AC"
			return a, tick(140*time.Millisecond, "key")

		case "+/-":
			a.engine.ChangeSign()
			a.pressedKey = "+/-"
			return a, tick(140*time.Millisecond, "key")
		}
	}
	return a, nil
}

func (a *App) View() string {
	// Styles (reusing gostations idioms: 63 for accents/flashes, 238 subtle borders, 46 green LCD, 235 bg)
	outer := lipgloss.NewStyle().
		Border(lipgloss.RoundedBorder()).
		BorderForeground(lipgloss.Color("63")).
		Padding(1, 2)

	flashStyle := lipgloss.NewStyle().
		Foreground(lipgloss.Color("15")).
		Background(lipgloss.Color("63")).
		Bold(true).
		Align(lipgloss.Center)

	// Compute maximal width for the main display (full span inside the card)
	dispW := a.width - 8 // outer border + padding + breathing room
	if dispW < 40 {
		dispW = 50
	}

	// Base indicator at the *start* of the main display row, e.g. [BIN]
	baseLabel := "[" + string(a.engine.CurrentBase()) + "]"
	baseSt := lipgloss.NewStyle().Foreground(lipgloss.Color("245")).Bold(true)
	if a.flash == "base" {
		baseSt = flashStyle
	}
	basePart := baseSt.Render(baseLabel)

	// Number (or CERR during flash). Right-aligned in the remaining wide space.
	num := a.engine.FormatForDisplay()
	if a.cerrFlash {
		num = "CERR"
	}

	numW := dispW - lipgloss.Width(basePart) - 4 // gap + padding
	if numW < 10 {
		numW = 10
	}
	numSt := lipgloss.NewStyle().
		Background(lipgloss.Color("235")).
		Foreground(lipgloss.Color("46")).
		Width(numW).
		Align(lipgloss.Right).
		Padding(0, 1)

	numPart := numSt.Render(num)
	if a.cerrFlash {
		numPart = flashStyle.Width(numW).Align(lipgloss.Right).Padding(0, 1).Render("CERR")
	}

	// Single main display row: base on left + wide right-aligned number.
	// This spans the full maximal width of the panel.
	displayRow := lipgloss.JoinHorizontal(lipgloss.Left, basePart, "  ", numPart)

	// The LCD container provides the bordered panel with vertical padding
	// for "large" visual weight. The row inside uses the full width.
	lcd := lipgloss.NewStyle().
		Background(lipgloss.Color("235")).
		Border(lipgloss.NormalBorder()).
		BorderForeground(lipgloss.Color("238")).
		Padding(1, 1). // vertical padding gives the row height/weight
		Width(dispW)

	display := lcd.Render(displayRow)

	// --- Tactile keypad decoration ---
	// Base style for a "key": bordered, slightly raised look with dark background.
	// This gives each button a physical, tactile calculator key appearance.
	keyStyle := lipgloss.NewStyle().
		Width(5).
		Height(2).
		Align(lipgloss.Center).
		Border(lipgloss.NormalBorder()).
		BorderForeground(lipgloss.Color("238")).
		Background(lipgloss.Color("236")).
		Foreground(lipgloss.Color("250"))

	// Pressed/activated style: bright inversion for that "key is being pressed" feel.
	pressedStyle := flashStyle.
		Border(lipgloss.NormalBorder()).
		BorderForeground(lipgloss.Color("63")).
		Width(5).
		Height(2).
		Align(lipgloss.Center)

	// Specialized key styles for visual grouping (like real calculators).
	numKey := keyStyle
	opKey := keyStyle.Foreground(lipgloss.Color("63")).Background(lipgloss.Color("235"))
	clearKey := keyStyle.Foreground(lipgloss.Color("203")).Background(lipgloss.Color("52"))
	modKey := keyStyle.Foreground(lipgloss.Color("214"))                                   // orange-ish for MOD
	hexKey := keyStyle.Foreground(lipgloss.Color("214")).Background(lipgloss.Color("235")) // for A-F, only shown in HEX mode

	makeKey := func(label string) string {
		var st lipgloss.Style
		switch label {
		case "+", "-", "*", "/", "=":
			st = opKey
		case "C", "AC":
			st = clearKey
		case "MOD":
			st = modKey
		case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", ".":
			st = numKey
		case "+/-":
			st = opKey
		default:
			st = keyStyle
		}
		if a.pressedKey == label {
			st = pressedStyle
		}
		return st.Render(label)
	}

	spacer := "  " // gap between keys for tactile separation
	row1 := lipgloss.JoinHorizontal(lipgloss.Top, makeKey("7"), spacer, makeKey("8"), spacer, makeKey("9"), spacer, makeKey("/"), spacer, makeKey("MOD"))
	row2 := lipgloss.JoinHorizontal(lipgloss.Top, makeKey("4"), spacer, makeKey("5"), spacer, makeKey("6"), spacer, makeKey("*"), spacer, makeKey("C"))
	row3 := lipgloss.JoinHorizontal(lipgloss.Top, makeKey("1"), spacer, makeKey("2"), spacer, makeKey("3"), spacer, makeKey("-"), spacer, makeKey("AC"))
	row4 := lipgloss.JoinHorizontal(lipgloss.Top, makeKey("0"), spacer, makeKey("."), spacer, makeKey("+/-"), spacer, makeKey("+"), spacer, makeKey("="))

	var rawGrid string
	if a.engine.CurrentBase() == calc.BaseHEX {
		// HEX mode only: A-F row appears at the top of the keypad (only after Tab into HEX).
		// Use dedicated hexBtn to force hexKey style (avoids label conflict with "C" clear button).
		hexBtn := func(label string) string {
			st := hexKey
			if a.pressedKey == label {
				st = pressedStyle
			}
			return st.Render(label)
		}
		hexRow := lipgloss.JoinHorizontal(lipgloss.Top,
			hexBtn("A"), spacer, hexBtn("B"), spacer, hexBtn("C"), spacer, hexBtn("D"), spacer, hexBtn("E"), spacer, hexBtn("F"),
		)
		hexW := lipgloss.Width(hexRow)
		// Robust per-line centering of the pre-joined 5-key rows under the 6-key hex row.
		// We pad each individual line of the row block explicitly. This avoids any subtle
		// artifacts from Style.Width+Align or PlaceHorizontal when the input is already a
		// multi-line string containing ANSI border sequences. Ensures every line (including
		// the bottom border lines of the last row) has exactly the same width so vertical
		// borders and bottom edges line up cleanly with no dangling fragments or splits.
		centerUnderHex := func(block string) string {
			if block == "" {
				return block
			}
			lines := strings.Split(block, "\n")
			for i, line := range lines {
				cw := lipgloss.Width(line)
				if cw >= hexW {
					continue
				}
				pad := hexW - cw
				left := pad / 2
				right := pad - left
				lines[i] = strings.Repeat(" ", left) + line + strings.Repeat(" ", right)
			}
			return strings.Join(lines, "\n")
		}
		row1 = centerUnderHex(row1)
		row2 = centerUnderHex(row2)
		row3 = centerUnderHex(row3)
		row4 = centerUnderHex(row4)
		rawGrid = lipgloss.JoinVertical(lipgloss.Left, hexRow, row1, row2, row3, row4)
	} else {
		// Normal mode: standard 4-row grid (no A-F)
		rawGrid = lipgloss.JoinVertical(lipgloss.Left, row1, row2, row3, row4)
	}

	// Center the key grid directly under the display.
	// No enclosing container — just the individually styled keys.
	// When in HEX the A-F row appears at the top of the keypad.
	// Explicit per-line centering of the entire rawGrid (the stacked hex+arith rows,
	// where arith rows are already internally padded to hexW) into dispW.
	// We do this manually instead of lipgloss.NewStyle().Width(dispW).Align(Center).Render
	// because the latter was producing inconsistent left padding on certain lines
	// (especially bottom border lines containing box-drawing chars + heavy ANSI),
	// causing the bottoms of the last row's keys to shift 1-2 columns relative to
	// their own tops and sides.
	kpLines := strings.Split(rawGrid, "\n")
	for j := range kpLines {
		cw := lipgloss.Width(kpLines[j])
		if cw < dispW {
			p := dispW - cw
			l := p / 2
			r := p - l
			kpLines[j] = strings.Repeat(" ", l) + kpLines[j] + strings.Repeat(" ", r)
		}
	}
	keypad := strings.Join(kpLines, "\n")

	// Hint (minimal, non-wrapping, like gostations final player)
	hint := lipgloss.NewStyle().Faint(true).Render("Tab:BASE  m:MOD  BackSpace:C  Del:AC")
	centeredHint := lipgloss.NewStyle().Width(dispW).Align(lipgloss.Center).Render(hint)

	inner := lipgloss.JoinVertical(lipgloss.Left,
		lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("63")).Render("gralculator"),
		"",
		display,
		"",
		keypad,
		"",
		centeredHint,
	)

	// Center the whole card (content-sized, not stretched). The display inside now uses full width.
	card := outer.Render(inner)
	return lipgloss.Place(a.width, a.height, lipgloss.Center, lipgloss.Center, card)
}

// Run is a convenience for main.go (spike).
func Run() error {
	p := tea.NewProgram(NewApp(), tea.WithAltScreen())
	_, err := p.Run()
	return err
}