package main

import (
	"strings"
	"time"

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

const (
	diffletWidth                = 9
	diffletHeight               = 4
	diffletGap                  = 2
	diffletMinimumHeaderWidth   = 10
	diffletFallbackRightPadding = 1
)

type DiffletExpression string

const (
	DiffletIdle      DiffletExpression = "idle"
	DiffletFocused   DiffletExpression = "focused"
	DiffletHappy     DiffletExpression = "happy"
	DiffletApproved  DiffletExpression = "approved"
	DiffletSurprised DiffletExpression = "surprised"
	DiffletConcerned DiffletExpression = "concerned"
	DiffletConfused  DiffletExpression = "confused"
	DiffletSad       DiffletExpression = "sad"
	DiffletAnnoyed   DiffletExpression = "annoyed"
	DiffletError     DiffletExpression = "error"
	DiffletSleeping  DiffletExpression = "sleeping"
	DiffletCurious   DiffletExpression = "curious"
)

var diffletFaces = map[DiffletExpression]string{
	DiffletIdle:      "•_•",
	DiffletFocused:   "-_-",
	DiffletHappy:     "^_^",
	DiffletApproved:  "^o^",
	DiffletSurprised: "•o•",
	DiffletConcerned: "•^•",
	DiffletConfused:  "•~•",
	DiffletSad:       ";_;",
	DiffletAnnoyed:   ">_<",
	DiffletError:     "x_x",
	DiffletSleeping:  "u_u",
	DiffletCurious:   "o_o",
}

type DiffletFrame struct {
	Expression DiffletExpression
	Feet       string
}

func (frame DiffletFrame) lines() []string {
	feet := frame.Feet
	if feet == "" {
		feet = " ▝     ▘"
	}
	return []string{
		"▄███████▄",
		"█+ " + diffletFaces[frame.Expression] + " -█",
		"▀███████▀",
		feet + strings.Repeat(" ", max(0, diffletWidth-lipgloss.Width(feet))),
	}
}

func (frame DiffletFrame) render() []string {
	lines := frame.lines()
	lines[1] = "█" + okStyle.Render("+") + " " + diffletFaces[frame.Expression] +
		" " + badStyle.Render("-") + "█"
	return lines
}

type diffletAnimation struct {
	frames   []DiffletFrame
	interval time.Duration
	loop     bool
	settle   DiffletExpression
}

type diffletState int

const (
	diffletIdle diffletState = iota
	diffletLoading
	diffletFocused
	diffletConcerned
	diffletHappy
	diffletApproved
	diffletSleeping
	diffletNewComment
	diffletSuccess
	diffletRecoverableError
	diffletFatalError
	diffletSad
)

type diffletTickMsg struct {
	generation uint64
}

type diffletModel struct {
	enabled    bool
	visible    bool
	expressive bool
	animated   bool
	state      diffletState
	expression DiffletExpression
	animation  diffletAnimation
	frame      int
	generation uint64
	blinking   bool
	blinkCycle uint64
}

func newDifflet(enabled, expressive, animated bool) diffletModel {
	model := diffletModel{
		enabled: enabled, visible: true, expressive: expressive, animated: animated,
		state: diffletLoading, expression: DiffletIdle,
	}
	_ = model.setState(diffletLoading)
	return model
}

func (d *diffletModel) start() tea.Cmd {
	if !d.enabled || !d.visible || !d.animated {
		return nil
	}
	if d.state == diffletIdle {
		return d.tick(d.blinkDelay())
	}
	if len(d.animation.frames) > 0 {
		return d.tick(d.animation.interval)
	}
	return nil
}

func (d *diffletModel) setState(state diffletState) tea.Cmd {
	d.state = state
	d.generation++
	d.frame = 0
	d.blinking = false
	d.animation = diffletAnimation{}
	d.expression = d.staticExpression(state)
	if !d.enabled || !d.visible || !d.animated {
		return nil
	}

	switch state {
	case diffletIdle:
		return d.tick(d.blinkDelay())
	case diffletLoading:
		d.animation = diffletAnimation{
			frames: []DiffletFrame{
				{Expression: DiffletIdle, Feet: " ▝     ▘"},
				{Expression: DiffletIdle, Feet: "  ▝   ▘"},
				{Expression: DiffletIdle, Feet: "   ▝ ▘"},
				{Expression: DiffletIdle, Feet: "  ▝   ▘"},
			},
			interval: 180 * time.Millisecond,
			loop:     true,
			settle:   DiffletIdle,
		}
	case diffletNewComment:
		d.animation = diffletAnimation{
			frames: []DiffletFrame{
				{Expression: DiffletIdle},
				{Expression: DiffletSurprised},
				{Expression: DiffletConcerned},
			},
			interval: 200 * time.Millisecond,
			settle:   DiffletConcerned,
		}
	case diffletSuccess:
		d.animation = diffletAnimation{
			frames: []DiffletFrame{
				{Expression: DiffletIdle},
				{Expression: DiffletHappy},
				{Expression: DiffletApproved},
				{Expression: DiffletHappy},
			},
			interval: 175 * time.Millisecond,
			settle:   DiffletHappy,
		}
	case diffletRecoverableError:
		if d.expressive {
			d.animation = diffletAnimation{
				frames: []DiffletFrame{
					{Expression: DiffletIdle},
					{Expression: DiffletAnnoyed},
					{Expression: DiffletSad},
				},
				interval: 220 * time.Millisecond,
				settle:   DiffletSad,
			}
		}
	case diffletFatalError:
		if d.expressive {
			d.animation = diffletAnimation{
				frames: []DiffletFrame{
					{Expression: DiffletIdle},
					{Expression: DiffletAnnoyed},
					{Expression: DiffletError},
				},
				interval: 220 * time.Millisecond,
				settle:   DiffletError,
			}
		}
	}
	if len(d.animation.frames) == 0 {
		return nil
	}
	d.expression = d.animation.frames[0].Expression
	return d.tick(d.animation.interval)
}

func (d *diffletModel) setVisible(visible bool) tea.Cmd {
	if d.visible == visible {
		return nil
	}
	d.visible = visible
	if !visible {
		d.generation++
		d.animation = diffletAnimation{}
		d.blinking = false
		return nil
	}
	return d.setState(d.state)
}

func (d *diffletModel) staticExpression(state diffletState) DiffletExpression {
	switch state {
	case diffletFocused:
		return DiffletFocused
	case diffletConcerned, diffletNewComment:
		return DiffletConcerned
	case diffletHappy, diffletSuccess:
		return DiffletHappy
	case diffletApproved:
		return DiffletApproved
	case diffletSleeping:
		return DiffletSleeping
	case diffletRecoverableError:
		if d.expressive {
			return DiffletAnnoyed
		}
		return DiffletConcerned
	case diffletFatalError:
		return DiffletError
	case diffletSad:
		if d.expressive {
			return DiffletSad
		}
		return DiffletConcerned
	default:
		return DiffletIdle
	}
}

func (d *diffletModel) update(msg diffletTickMsg) tea.Cmd {
	if !d.enabled || !d.visible || !d.animated || msg.generation != d.generation {
		return nil
	}
	if d.state == diffletIdle {
		if !d.blinking {
			d.blinking = true
			d.expression = DiffletFocused
			return d.tick(125 * time.Millisecond)
		}
		d.blinking = false
		d.expression = DiffletIdle
		d.blinkCycle++
		return d.tick(d.blinkDelay())
	}
	if len(d.animation.frames) == 0 {
		return nil
	}
	next := d.frame + 1
	if next >= len(d.animation.frames) {
		if !d.animation.loop {
			settle := d.animation.settle
			d.animation = diffletAnimation{}
			d.expression = settle
			return nil
		}
		next = 0
	}
	d.frame = next
	d.expression = d.animation.frames[next].Expression
	return d.tick(d.animation.interval)
}

func (d diffletModel) frameLines() []string {
	if !d.enabled || !d.visible {
		return nil
	}
	if len(d.animation.frames) > 0 && d.frame < len(d.animation.frames) {
		frame := d.animation.frames[d.frame]
		frame.Expression = d.expression
		return frame.render()
	}
	return (DiffletFrame{Expression: d.expression}).render()
}

func diffletHeaderWidth(width int) int {
	centeredLeft := max(0, (width-diffletWidth)/2)
	if centeredLeft-diffletGap >= diffletMinimumHeaderWidth {
		return centeredLeft - diffletGap
	}
	rightPadding := 0
	if width-diffletWidth-diffletGap > 1 {
		rightPadding = diffletFallbackRightPadding
	}
	return max(1, width-diffletWidth-diffletGap-rightPadding)
}

func (d diffletModel) tick(after time.Duration) tea.Cmd {
	generation := d.generation
	return tea.Tick(after, func(time.Time) tea.Msg {
		return diffletTickMsg{generation: generation}
	})
}

func (d diffletModel) blinkDelay() time.Duration {
	return 5*time.Second + time.Duration((d.generation+d.blinkCycle*3)%6)*650*time.Millisecond
}