package page

import (
	"fmt"
	"math"
	"path/filepath"
	"strings"

	"github.com/go-gl/gl/v3.3-core/gl"
	"github.com/veandco/go-sdl2/sdl"
	"rhemawavetech.com/rhemawave/internal/colors"
	"rhemawavetech.com/rhemawave/internal/db"
	"rhemawavetech.com/rhemawave/internal/fontManager"
	"rhemawavetech.com/rhemawave/internal/logger"
	"rhemawavetech.com/rhemawave/internal/mixer"
	colorPattern "rhemawavetech.com/rhemawave/internal/pattern/color"
	linePattern "rhemawavetech.com/rhemawave/internal/pattern/line"
	"rhemawavetech.com/rhemawave/internal/shaderManager"
)

const (
	defaultProclamationID        string = "f3d42354-3197-45e4-9b08-be447f14386d"
	proclamationPlayCount        int    = 10
	defaultProclamationPlayCount int    = 1
)

type Line struct {
	words []StringItem
	width int32
}

// proclamationStream tracks one proclamation and how many full loops it should play.
type proclamationStream struct {
	name      string
	words     []string
	repeat    int
	completed int
	wordIndex int
}

// LineDeque is a double-ended queue for Line values backed by a circular buffer.
// It avoids O(n) prepend and prevents capacity leaks from head-of-slice removal.
type LineDeque struct {
	buf        []Line
	head, tail int
	count      int
}

func NewLineDeque(cap int) *LineDeque {
	if cap < 4 {
		cap = 4
	}
	return &LineDeque{buf: make([]Line, cap)}
}

func (d *LineDeque) Len() int { return d.count }

func (d *LineDeque) grow() {
	newCap := len(d.buf) * 2
	newBuf := make([]Line, newCap)
	for i := 0; i < d.count; i++ {
		newBuf[i] = d.buf[(d.head+i)%len(d.buf)]
	}
	d.buf = newBuf
	d.head = 0
	d.tail = d.count
}

func (d *LineDeque) PushBack(l Line) {
	if d.count == len(d.buf) {
		d.grow()
	}
	d.buf[d.tail] = l
	d.tail = (d.tail + 1) % len(d.buf)
	d.count++
}

func (d *LineDeque) PushFront(l Line) {
	if d.count == len(d.buf) {
		d.grow()
	}
	d.head = (d.head - 1 + len(d.buf)) % len(d.buf)
	d.buf[d.head] = l
	d.count++
}

func (d *LineDeque) PopFront() Line {
	l := d.buf[d.head]
	d.buf[d.head] = Line{} // clear for GC
	d.head = (d.head + 1) % len(d.buf)
	d.count--
	return l
}

func (d *LineDeque) PopBack() Line {
	d.tail = (d.tail - 1 + len(d.buf)) % len(d.buf)
	l := d.buf[d.tail]
	d.buf[d.tail] = Line{} // clear for GC
	d.count--
	return l
}

func (d *LineDeque) Front() Line { return d.buf[d.head] }

func (d *LineDeque) Back() Line {
	return d.buf[(d.tail-1+len(d.buf))%len(d.buf)]
}

func (d *LineDeque) Get(i int) *Line {
	return &d.buf[(d.head+i)%len(d.buf)]
}

func (d *LineDeque) Set(i int, l Line) {
	d.buf[(d.head+i)%len(d.buf)] = l
}

func (d *LineDeque) Clear() {
	for i := 0; i < d.count; i++ {
		d.buf[(d.head+i)%len(d.buf)] = Line{}
	}
	d.head, d.tail, d.count = 0, 0, 0
}

type ScrollerPage struct {
	Base

	streams     []proclamationStream
	streamIndex int

	lines         *LineDeque
	lineHeight    int32
	shader        *shaderManager.Shader
	activePattern linePattern.LinePattern
	font          *fontManager.FontEntry
	spaceWidth    int32
	lineCtx       *linePattern.LineRenderContext
	colorPattern  *colorPattern.ColorPattern
	scrollOffset  float32
	scrollY       float32
	fontScale     float32

	// Reuse one GL texture per unique word.
	wordTextureCache map[string]StringItem

	increment float32
	velocity  float32

	// Time-based velocity control
	velocityFloor     float32
	velocityCeiling   float32
	velocityStep      float32
	velocityDelay     float32
	velocityDirection int
	velocityTimer     float32
	velocityState     int
	autoVelocity      bool
	hold              float32
}

func (p *ScrollerPage) Init(ctx *PageCtx) error {
	p.increment = 100.0
	p.velocity = 800.0
	p.SetAutoVelocity(true, -4000.0, 4000.0, 100.0, 2.5, 6.0)

	sm := shaderManager.Get()
	fm := fontManager.Get()

	// Get font
	font, ok := fm.GetFont("Scrambled")
	if !ok {
		return fmt.Errorf("unable to fetch font 'Scrambled'")
	}
	p.font = font
	logger.Info("Font name: %s", font.Name)

	p.Base.Init(ctx)

	// Get text shader
	textShader, ok := sm.Get("text")
	if !ok {
		return fmt.Errorf("text shader not found")
	}
	p.shader = textShader
	logger.Info("Shader Program ID: %d", textShader.ProgramID)
	logger.Info("p.shader Program ID: %d", p.shader.ProgramID)

	p.wordTextureCache = make(map[string]StringItem, 256)

	// Load proclamation streams from database
	if err := p.loadProclamations(); err != nil {
		logger.Error("Error loading proclamations: %v", err)
		p.Context.NavigateTo(PROCLAMATIONS)
		return nil
	}

	// Get line pattern from database
	var err error
	linePatternName := p.Context.CfgPtr.LinePattern

	p.activePattern, err = linePattern.Get(linePatternName)
	if err != nil {
		return fmt.Errorf("failed to load line pattern '%s': %w", linePatternName, err)
	}

	// Initialize color pattern
	baseColors := []sdl.Color{
		colors.Tan,
		colors.PeachPuff,
		colors.LightCyan,
		colors.LightSeaGreen,
		colors.MediumTurquoise,
		colors.DarkCyan,
		colors.MediumPurple,
	}
	p.colorPattern = colorPattern.NewColorPattern(baseColors)

	// Font setup
	p.fontScale = float32(32) / float32(p.Context.CfgPtr.StandardFontSize)
	nLines := int(float32(p.ScreenHeight) / 32.0)
	p.lines = NewLineDeque(nLines * 2)

	// Calculate space width using the scale ratio.
	spaceGlyph, ok := fm.GetGlyph(font.Name, ' ')
	if !ok {
		return fmt.Errorf("failed to get space glyph")
	}
	p.spaceWidth = int32(float32(spaceGlyph.Advance) * p.fontScale)

	// Get line height using the same scale ratio.
	tmpStrID, _, H, err := fm.NewCreateStringTexture(font.Name, "Mg", p.shader)
	if err != nil {
		return fmt.Errorf("failed to create sample texture: %w", err)
	}
	p.lineHeight = int32(float32(H) * p.fontScale)
	gl.DeleteTextures(1, &tmpStrID)

	p.lineCtx = &linePattern.LineRenderContext{
		ScreenWidth: p.ScreenWidth,
		Font:        font,
		FontScale:   p.fontScale,
		SpaceWidth:  p.spaceWidth,
	}

	// Create initial lines
	for i := range nLines {
		if err := p.createLine(i, true); err != nil {
			return fmt.Errorf("failed to create initial line %d: %w", i, err)
		}
	}

	// Audio setup
	audioDeviceName := p.Context.CfgPtr.SelectedAudioDevice
	if mixer.CurrentDevice() != audioDeviceName {
		if err := mixer.SwitchDevice(audioDeviceName); err != nil {
			logger.Error("failed to switch audio device: %v", err)
		}
	}

	assetsDir := p.Context.CfgPtr.AssetsDir
	audioFile := filepath.Join(assetsDir, "audio/audio.wav")
	logger.Info("Attempting to play %s", audioFile)
	if err := mixer.Play(audioFile, true, p.Context.CfgPtr); err != nil {
		logger.Error("Mixer returned an error: %v", err)
	}

	currentDevice := mixer.CurrentDevice()
	if currentDevice == "" {
		currentDevice = "default"
	}
	_ = currentDevice

	return nil
}

// loadProclamations loads selected proclamations as stream units (not one giant word list).
func (p *ScrollerPage) loadProclamations() error {
	p.streams = p.streams[:0]

	var selected []db.Proclamation
	if err := p.Context.DbPtr.Where("selected = ?", true).Find(&selected).Error; err != nil {
		return err
	}

	var defaultProclamation db.Proclamation
	if err := p.Context.DbPtr.Where("ID = ?", defaultProclamationID).First(&defaultProclamation).Error; err != nil {
		return err
	}
	defaultWords := strings.Fields(defaultProclamation.Content)

	// Build interleaved stream:
	// each selected proclamation repeats N times, then default repeats once.
	for _, proclamation := range selected {
		// Prevent default proclamation from being treated as a normal selected proclamation.
		if proclamation.ID == defaultProclamationID {
			continue
		}

		words := strings.Fields(proclamation.Content)
		if len(words) == 0 {
			continue
		}

		p.streams = append(p.streams, proclamationStream{
			name:   proclamation.Name,
			words:  words,
			repeat: proclamationPlayCount, // 10
		})

		if len(defaultWords) > 0 {
			p.streams = append(p.streams, proclamationStream{
				name:   defaultProclamation.Name,
				words:  defaultWords,
				repeat: 1, // play once between selected proclamations
			})
		}
	}

	// Fallback: if no non-default selected proclamations, at least play default.
	if len(p.streams) == 0 && len(defaultWords) > 0 {
		p.streams = append(p.streams, proclamationStream{
			name:   defaultProclamation.Name,
			words:  defaultWords,
			repeat: 1,
		})
	}

	if len(p.streams) == 0 {
		return fmt.Errorf("failed to load proclamations: no proclamation words available")
	}

	p.streamIndex = 0
	return nil
}

// nextLineWords gets words for the current line and advances proclamation stream when needed.
func (p *ScrollerPage) nextLineWords() []string {
	if len(p.streams) == 0 {
		return nil
	}

	s := &p.streams[p.streamIndex]
	if len(s.words) == 0 {
		p.streamIndex = (p.streamIndex + 1) % len(p.streams)
		return p.nextLineWords()
	}

	prevIdx := s.wordIndex
	words := p.activePattern.GetNextLine(s.words, &s.wordIndex, p.lineCtx)

	// If word index wraps, one full proclamation pass completed.
	if s.wordIndex < prevIdx {
		s.completed++
		targetRepeats := s.repeat
		if targetRepeats <= 0 {
			targetRepeats = 1
		}
		logger.Debug("Now playing proclamation: %s", s.name)
		if s.completed >= targetRepeats {
			logger.Debug("Advancing proclamation stream: %s", s.name)
			s.completed = 0
			s.wordIndex = 0
			p.streamIndex = (p.streamIndex + 1) % len(p.streams)
		}
	}

	return words
}

// getCachedWord returns a reusable textured StringItem for a word.
func (p *ScrollerPage) getCachedWord(word string) (StringItem, error) {
	if cached, ok := p.wordTextureCache[word]; ok {
		return cached, nil
	}

	base, err := NewStringItem(word, p.font, sdl.Color{R: 255, G: 255, B: 255, A: 255})
	if err != nil {
		return StringItem{}, fmt.Errorf("unable to create cached string item for word '%s': %w", word, err)
	}
	base.Scale(p.fontScale)

	p.wordTextureCache[word] = base
	return base, nil
}

// buildLineFromWords builds a line using cached texture IDs and per-instance color/position.
func (p *ScrollerPage) buildLineFromWords(words []string) (Line, error) {
	line := Line{words: []StringItem{}}

	for _, word := range words {
		if word == "" {
			continue
		}

		cached, err := p.getCachedWord(word)
		if err != nil {
			return Line{}, err
		}

		item := cached
		item.Color = p.colorPattern.Color()

		if len(line.words) > 0 {
			line.width += p.spaceWidth
		}
		line.words = append(line.words, item)
		line.width += item.W
	}

	return line, nil
}

// positionLine sets X/Y for all words in a line.
func (p *ScrollerPage) positionLine(line *Line, baseY int32) {
	startX := p.ScreenCenterX - (line.width / 2)
	for j := range line.words {
		if j == 0 {
			line.words[j].X = startX
		} else {
			line.words[j].X = line.words[j-1].X + line.words[j-1].W + p.spaceWidth
		}
		line.words[j].Y = baseY
	}
}

// createLine is a helper to generate a new line at a specific index.
// isInitial determines if this is during initialization (positions from top)
// or dynamic creation (positions relative to existing lines).
func (p *ScrollerPage) createLine(index int, isInitial bool) error {
	words := p.nextLineWords()
	line, err := p.buildLineFromWords(words)
	if err != nil {
		return err
	}

	var baseY int32
	if isInitial {
		baseY = int32(p.scrollY) - int32(p.lineHeight)*int32(index)
	} else {
		baseY = 0
	}
	p.positionLine(&line, baseY)

	if isInitial {
		p.lines.PushBack(line)
	}

	return nil
}

func (p *ScrollerPage) HandleEvent(event *sdl.Event) error {
	switch e := (*event).(type) {
	case *sdl.KeyboardEvent:
		if e.Type != sdl.KEYDOWN {
			return nil
		}
		switch e.Keysym.Sym {
		case sdl.K_UP:
			if !p.autoVelocity {
				p.velocity += p.increment
			}
		case sdl.K_DOWN:
			if !p.autoVelocity {
				p.velocity -= p.increment
			}
		}
		return nil
	}
	return nil
}

func (p *ScrollerPage) Update(dt float32) error {
	p.updateAutoVelocity(dt)

	p.scrollOffset += dt * p.velocity
	move := int32(p.scrollOffset)
	if move == 0 {
		return nil
	}
	p.scrollOffset -= float32(move)

	// Move all lines vertically
	for i := 0; i < p.lines.Len(); i++ {
		line := p.lines.Get(i)
		for j := range line.words {
			line.words[j].Y += move
		}
	}

	// Handle line replacement based on scroll direction
	if p.velocity > 0 {
		// Moving up: replace lines that go off top
		for p.lines.Len() > 0 && len(p.lines.Front().words) > 0 && p.lines.Front().words[0].Y > p.ScreenHeight {
			_ = p.lines.PopFront() // no texture delete; textures are shared via cache

			if err := p.addLineAtBottom(); err != nil {
				return err
			}
		}
	} else if p.velocity < 0 {
		// Moving down: replace lines that go off bottom
		for p.lines.Len() > 0 {
			back := p.lines.Back()
			if len(back.words) == 0 || back.words[0].Y+back.words[0].H >= 0 {
				break
			}

			_ = p.lines.PopBack() // no texture delete; textures are shared via cache

			if err := p.addLineAtTop(); err != nil {
				return err
			}
		}
	}

	return nil
}

// addLineAtBottom creates and adds a new line at the bottom of the display.
func (p *ScrollerPage) addLineAtBottom() error {
	newWords := p.nextLineWords()
	line, err := p.buildLineFromWords(newWords)
	if err != nil {
		return err
	}

	var baseY int32
	if p.lines.Len() > 0 && len(p.lines.Back().words) > 0 {
		baseY = p.lines.Back().words[0].Y - int32(p.lineHeight)
	} else {
		baseY = -int32(p.lineHeight)
	}

	p.positionLine(&line, baseY)
	p.lines.PushBack(line)
	return nil
}

// addLineAtTop creates and adds a new line at the top of the display.
func (p *ScrollerPage) addLineAtTop() error {
	newWords := p.nextLineWords()
	line, err := p.buildLineFromWords(newWords)
	if err != nil {
		return err
	}

	var baseY int32
	if p.lines.Len() > 0 && len(p.lines.Front().words) > 0 {
		baseY = p.lines.Front().words[0].Y + int32(p.lineHeight)
	} else {
		baseY = p.ScreenHeight
	}

	p.positionLine(&line, baseY)
	p.lines.PushFront(line)
	return nil
}

func (p *ScrollerPage) Render() error {
	p.BeginTextureRendering(p.shader)
	for i := 0; i < p.lines.Len(); i++ {
		line := p.lines.Get(i)
		for _, word := range line.words {
			if word.ID == 0 {
				continue
			}
			p.RenderTextureBatched(p.shader, word.ID, word.Position(), word.RawDimensions(), word.Color)
		}
	}
	p.EndTextureRendering()
	return nil
}

func (p *ScrollerPage) Destroy() error {
	if p == nil {
		return nil
	}

	mixer.Stop(1000, p.Context.CfgPtr)

	// Delete each cached word texture exactly once.
	for k, item := range p.wordTextureCache {
		if item.ID != 0 {
			id := item.ID
			gl.DeleteTextures(1, &id)
		}
		delete(p.wordTextureCache, k)
	}

	gl.Flush()

	// Drop references for GC safely
	p.lines = nil
	p.streams = nil
	p.lineCtx = nil
	p.font = nil
	p.shader = nil
	p.colorPattern = nil
	p.wordTextureCache = nil

	return nil
}

// SetAutoVelocity configures the automatic velocity system for the ScrollerPage.
func (p *ScrollerPage) SetAutoVelocity(enabled bool, floor, ceiling, step, delay, hold float32) {
	p.autoVelocity = enabled
	p.velocityFloor = -float32(math.Abs(float64(floor)))
	p.velocityCeiling = float32(math.Abs(float64(ceiling)))
	p.velocityStep = float32(math.Abs(float64(step)))
	p.velocityDelay = delay
	p.hold = hold

	// Initialize state
	p.velocityDirection = 1
	p.velocityState = 0
	p.velocityTimer = 0.0
	p.velocity = p.velocityFloor
}

// updateAutoVelocity handles automatic velocity changes.
func (p *ScrollerPage) updateAutoVelocity(dt float32) {
	if !p.autoVelocity {
		return
	}

	switch p.velocityState {
	case 0: // Changing velocity
		if p.velocityDirection == 1 {
			p.velocity += p.velocityStep * dt
			if p.velocity >= p.velocityCeiling {
				p.velocity = p.velocityCeiling
				p.velocityState = 1
				p.velocityTimer = 0.0
			}
		} else {
			p.velocity -= p.velocityStep * dt
			if p.velocity <= p.velocityFloor {
				p.velocity = p.velocityFloor
				p.velocityState = 2
				p.velocityTimer = 0.0
			}
		}

	case 1: // Waiting at ceiling
		p.velocityTimer += dt
		if p.velocityTimer >= p.velocityDelay {
			p.velocityDirection = -1
			p.velocityState = 0
		}

	case 2: // Waiting at floor
		p.velocityTimer += dt
		if p.velocityTimer >= p.velocityDelay {
			p.velocityDirection = 1
			p.velocityState = 0
		}
	}
}