package main

import (
	"fmt"
	"math"
	"strings"
	"unicode"

	"git.sentinel65x.com/dave/gary/debugger/memory"
	tea "github.com/charmbracelet/bubbletea"
	lip "github.com/charmbracelet/lipgloss"
	"github.com/creachadair/mds/slice"
)

type HexViewSetHeight struct {
	Height int
}

type HexView struct {
	AddrStyle lip.Style
	ZeroStyle lip.Style
	HexStyle  lip.Style

	mem          *memory.Memory
	commit       func() tea.Cmd
	height       int
	firstAddr    int // top of viewport
	selectedAddr int
	editing      bool
	editNibble   int // 0 or 1
}

func NewHexView(mem *memory.Memory, commit func() tea.Cmd) HexView {
	st := lip.NewStyle()
	ret := HexView{
		AddrStyle: st,
		ZeroStyle: st,
		HexStyle:  st,
		mem:       mem,
		commit:    commit,
	}
	return ret
}

func (m HexView) Width() int {
	hexdumpWidth := 16*3 + 2     // including spaces between dquads
	addrWidth := m.addrNibbles() // Hex nibbles needed to represent all addrs
	return addrWidth + 4 + hexdumpWidth
}

func (m HexView) SelectedAddr() int {
	return m.selectedAddr
}

func (m *HexView) moveSelection(delta int) bool {
	newAddr := m.selectedAddr + delta
	if newAddr >= 0 && newAddr < m.mem.Len() {
		m.selectedAddr = newAddr
		start, end := m.VisibleBytes()
		newFirstLine := newAddr / 16
		if newAddr < start {
			newFirstLine = newFirstLine - (m.height * 4 / 5)
			newFirstLine = max(newFirstLine, 0)
			m.firstAddr = newFirstLine * 16
		} else if newAddr >= end {
			newFirstLine = newFirstLine - (m.height * 1 / 5)
			newFirstLine = min(newFirstLine, (m.mem.Len()/16)-m.height)
			m.firstAddr = newFirstLine * 16
		}
		return true
	}
	return false
}

func (m HexView) VisibleBytes() (start, end int) {
	return m.firstAddr, m.firstAddr + (m.height * 16)
}

func (m HexView) addrFormat() string {
	return fmt.Sprintf("%%%dx", m.addrNibbles())
}

func (m HexView) addrNibbles() int {
	return int(math.Ceil(math.Log2(float64(m.mem.Len())*8))) / 4
}

func (m HexView) Update(msg tea.Msg) (HexView, tea.Cmd) {
	if m.editing {
		return m.updateEditMode(msg)
	} else {
		return m.updateViewMode(msg)
	}
}

func (m HexView) updateEditMode(msg tea.Msg) (HexView, tea.Cmd) {
	switch msg := msg.(type) {
	case HexViewSetHeight:
		m.height = msg.Height
	case tea.KeyMsg:
		switch msg.Type {
		case tea.KeyLeft:
			if m.editNibble == 1 {
				m.editNibble = 0
			} else if m.moveSelection(-1) {
				m.editNibble = 1
			}
		case tea.KeyRight:
			if m.editNibble == 0 {
				m.editNibble = 1
			} else if m.moveSelection(1) {
				m.editNibble = 0
			}
		case tea.KeyUp:
			m.moveSelection(-16)
		case tea.KeyDown:
			m.moveSelection(16)
		case tea.KeyEsc:
			m.editing = false
		case tea.KeyEnter:
			m.editing = false
			return m, m.commit()
		case tea.KeyRunes:
			if unicode.In(msg.Runes[0], unicode.ASCII_Hex_Digit) {
				nibble := hexToNibble(msg.Runes[0])
				prev := m.mem.At(m.selectedAddr).Value
				if m.editNibble == 0 {
					m.mem.Write(m.selectedAddr, (nibble<<4)+(prev&0xF))
					m.editNibble++
				} else {
					m.mem.Write(m.selectedAddr, (prev&0xF0)+nibble)
					if m.moveSelection(1) {
						m.editNibble = 0
					}
				}
			}
		}
	}
	return m, nil
}

func hexToNibble(r rune) byte {
	switch {
	case r >= '0' && r <= '9':
		return byte(r - '0')
	case r >= 'a' && r <= 'f':
		return byte(r - 'a' + 10)
	case r >= 'A' && r <= 'F':
		return byte(r - 'A' + 10)
	}
	panic("invalid hex rune")
}

func (m HexView) updateViewMode(msg tea.Msg) (HexView, tea.Cmd) {
	switch msg := msg.(type) {
	case HexViewSetHeight:
		m.height = msg.Height
	case tea.KeyMsg:
		switch msg.String() {
		case "up":
			m.moveSelection(-16)
		case "down":
			m.moveSelection(16)
		case "left":
			m.moveSelection(-1)
		case "right":
			m.moveSelection(1)
		case "pgdown":
			m.moveSelection(m.height * 16)
		case "pgup":
			m.moveSelection(-m.height * 16)
		case "w":
			m.editing = true
			m.editNibble = 0
		}
	}
	return m, nil
}

func (m HexView) View() string {
	startAddr, endAddr := m.VisibleBytes()
	bytes := m.mem.Slice(startAddr, endAddr)

	var ret strings.Builder
	addrFormat := m.addrFormat()
	for line, bytes := range slice.Chunks(bytes, 16) {
		lineAddr := m.firstAddr + (16 * line)
		ret.WriteString(m.AddrStyle.Render(fmt.Sprintf(addrFormat, lineAddr)))
		ret.WriteString("   ")
		for i, b := range bytes {
			byteAddr := lineAddr + i
			if i == 8 {
				ret.WriteString("   ")
			} else if i != 0 {
				ret.WriteByte(' ')
			}
			if m.editing && byteAddr == m.selectedAddr {
				st := m.HexStyle.Bold(true)
				s1, s2 := st.Reverse(true), st
				if m.editNibble == 1 {
					s1, s2 = s2, s1
				}
				ret.WriteString(s1.Render(fmt.Sprintf("%01x", b.Value>>4)))
				ret.WriteString(s2.Render(fmt.Sprintf("%01x", b.Value&0xF)))
			} else {
				st := m.HexStyle
				if m.selectedAddr == byteAddr {
					st = m.HexStyle.Reverse(true)
				} else if !b.Valid || b.Value == 0 {
					st = m.ZeroStyle
				}
				if b.Changed {
					st = st.Underline(true).Bold(true)
				}
				ret.WriteString(st.Render(b.Hex()))
			}
		}
		ret.WriteByte('\n')
	}
	return strings.TrimRight(ret.String(), "\n")
}