package command

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"git.gophernest.net/azpect/TextEditor/internal/action"
	"git.gophernest.net/azpect/TextEditor/internal/core"
	tea "github.com/charmbracelet/bubbletea"
)

// QuitMsg: Message signaling the application should quit.
type QuitMsg struct{}

// ErrorMsg: Message signaling an error to display.
type ErrorMsg struct {
	Err error
}

// --------------------------------------------------
// Quit Commands
// --------------------------------------------------

// cmdQuit: Handles :quit / :q command.
func cmdQuit(m action.Model, args []string, force bool) tea.Cmd {
	// :q! forces quit, ignoring unsaved changes
	if force {
		return tea.Quit
	}

	bufs := m.Buffers()

	// Cannot exit if any buffer has unsaved changes
	for _, buf := range bufs {
		if buf.Modified {
			m.SetCommandError(fmt.Errorf("unsaved changes to '%s'", buf.Filename))
			m.ActiveWindow().SetBuffer(buf)
			return nil
		}
	}

	return tea.Quit
}

// cmdQuitAll: Handles :qall / :qa command.
func cmdQuitAll(m action.Model, args []string, force bool) tea.Cmd {
	// TODO: Until splits are implemented, this is the same as cmdQuit
	return cmdQuit(m, args, force)
}

// --------------------------------------------------
// File Commands (write & edit)
// --------------------------------------------------

// cmdWrite: Handles :write / :w command
func cmdWrite(m action.Model, args []string, force bool) tea.Cmd {
	buf := m.ActiveBuffer()
	cmd, err := writeBuffer(m, buf, args, force)
	if err != nil {
		m.SetCommandError(err)
	}
	return cmd
}

// cmdWriteAll: Handles :wall / :wa command
func cmdWriteAll(m action.Model, args []string, force bool) tea.Cmd {
	var cmds []tea.Cmd

	bufs := m.Buffers()
	for _, buf := range bufs {
		if buf.Modified {
			cmd, err := writeBuffer(m, buf, args, force)
			if err != nil {
				m.SetCommandError(err)
				return nil
			}
			cmds = append(cmds, cmd)
		}
	}

	return tea.Batch(cmds...)
}

// cmdWriteQuit: Handles :wq command
func cmdWriteQuit(m action.Model, args []string, force bool) tea.Cmd {
	buf := m.ActiveBuffer()
	cmd, err := writeBuffer(m, buf, args, force)
	if err != nil {
		m.SetCommandError(err)
		return cmd
	}

	return tea.Batch(cmd, tea.Quit)
}

// cmdWriteQuitAll: Handles :wqall / :wqa / :xa command.
// Writes all modified buffers then quits.
func cmdWriteQuitAll(m action.Model, args []string, force bool) tea.Cmd {
	var cmds []tea.Cmd

	bufs := m.Buffers()
	for _, buf := range bufs {
		if buf.Modified {
			cmd, err := writeBuffer(m, buf, args, force)
			if err != nil {
				m.SetCommandError(err)
				return nil
			}
			cmds = append(cmds, cmd)
		}
	}

	cmds = append(cmds, tea.Quit)
	return tea.Batch(cmds...)
}

// cmdEdit: Handles :edit / :e
func cmdEdit(m action.Model, args []string, force bool) tea.Cmd {
	// must have arguments, cant edit nothing
	if len(args) < 1 {
		m.SetCommandError(fmt.Errorf(":edit requires an argument"))
		return nil
	}

	// Vim's Approach:
	// " When you do :edit filename.txt
	// 1. Check if file exists and is readable (if not, open new buffer)
	// 2. Detect file encoding (UTF-8, etc.)
	// 3. Read entire file into memory
	// 4. Split by line endings (respecting fileformat)
	// 5. Create new buffer with these lines
	// 6. Set buffer metadata:
	//    - buftype = "" (normal file)
	//    - modified = 0 (not modified)
	//    - fileformat = "unix" | "dos" | "mac"
	//    - fileencoding = "utf-8" (etc.)

	filename := args[0]
	ext := filepath.Ext(filename)

	// If the buffer already exists, just switch to it.
	bufs := m.Buffers()
	for _, buf := range bufs {
		if buf.Filename == filename {
			m.ActiveWindow().SetBuffer(buf)
			return nil
		}
	}

	file, err := os.Open(filename)
	notFound := errors.Is(err, os.ErrNotExist)

	if err != nil && !notFound {
		m.SetCommandError(err)
		return nil
	}
	if file != nil {
		defer file.Close()
	}

	// Create a buffer with the new file name, writing the file will
	// handle the saving logic
	if notFound {
		buf := core.NewBufferBuilder().
			WithType(core.FileBuffer).
			WithFilename(filename).
			WithFiletype(ext).
			Listed().
			Loaded().
			Build()

		m.SetBuffers(append(m.Buffers(), &buf))
		m.ActiveWindow().SetBuffer(&buf)

		// Need to adjust the cursor when we make a new file
		m.ActiveWindow().ClampCursor()
		return nil
	}

	var lines []string

	// BUG: We are unable to open and edit files owned by root. How do we handle that?

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := scanner.Text()
		line = strings.TrimSuffix(line, "\r")

		// BUG: This is bad, we don't want to this, but we have to
		cleaned := strings.ReplaceAll(line, "\t", strings.Repeat(" ", m.Settings().TabStop))
		lines = append(lines, cleaned)
	}

	buf := core.NewBufferBuilder().
		WithType(core.FileBuffer).
		WithFilename(filename).
		WithFiletype(ext).
		WithLines(lines).
		Listed().
		Loaded().
		Build()

	m.SetBuffers(append(m.Buffers(), &buf))
	m.ActiveWindow().SetBuffer(&buf)

	return nil
}

// --------------------------------------------------
// Register Commands
// --------------------------------------------------

// cmdRegisters: Handles :register command (debug - displays register content).
func cmdRegisters(m action.Model, args []string, force bool) tea.Cmd {
	// TODO: This is temporary, for debugging
	if len(args) < 1 {
		m.SetCommandError(fmt.Errorf("Please provide a name. Register dump not yet implemented."))
		return nil
	}

	if len(args[0]) != 1 {
		m.SetCommandError(fmt.Errorf("Name should be a single character."))
		return nil
	}

	name := rune(args[0][0])
	reg, found := m.GetRegister(name)
	if !found {
		m.SetCommandError(fmt.Errorf("Could not find register '%c'.", name))
		return nil
	}

	content := strings.Join(reg.Content, "\\n")
	t := reg.Type
	m.SetCommandOutput(fmt.Sprintf("Type: %d Name: \"%c Content: %s", t, name, content))
	return nil
}

// --------------------------------------------------
// Settings Commands
// --------------------------------------------------

// cmdSet: Handles :set option[=value] command for configuring editor settings.
// Examples:
//
//	:set number        - enable number
//	:set nonumber      - disable number
//	:set number!       - toggle number
//	:set tabstop=4     - set tabstop to 4
//	:set ts=4          - set tabstop to 4 (abbreviation)
func cmdSet(m action.Model, args []string, force bool) tea.Cmd {
	if len(args) == 0 {
		out := fmt.Sprintf("%+v", m.Settings())
		m.SetCommandOutput(out)
		return nil
	}

	for _, arg := range args {
		if err := parseSetOption(m, arg); err != nil {
			m.SetCommandError(err)
			return nil
		}
	}

	return nil
}

// Setting: Represents a configurable editor option.
type Setting struct {
	Name      string
	ShortForm string
	Type      SettingType
	Get       func(m action.Model) any
	Set       func(m action.Model, val any)
}

// SettingType: Enumeration of setting value types.
type SettingType int

const (
	BoolSetting SettingType = iota
	IntSetting
	StringSetting
)

// settingsMap defines all available settings (both global and window-local)
var settingsMap = []Setting{
	// Global editor settings
	{
		Name:      "tabstop",
		ShortForm: "ts",
		Type:      IntSetting,
		Get:       func(m action.Model) any { return m.Settings().TabStop },
		Set: func(m action.Model, val any) {
			s := m.Settings()
			s.TabStop = val.(int)
			m.SetSettings(s)
		},
	},
	// Window-local settings
	{
		Name:      "number",
		ShortForm: "nu",
		Type:      BoolSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.Number },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.Number = val.(bool)
			w.SetOptions(o)
		},
	},
	{
		Name:      "relativenumber",
		ShortForm: "rnu",
		Type:      BoolSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.RelativeNumber },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.RelativeNumber = val.(bool)
			w.SetOptions(o)
		},
	},
	{
		Name:      "scrolloff",
		ShortForm: "so",
		Type:      IntSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.ScrollOff },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.ScrollOff = val.(int)
			w.SetOptions(o)
		},
	},
	{
		Name:      "guttersize",
		ShortForm: "gu",
		Type:      IntSetting,
		Get:       func(m action.Model) any { return m.ActiveWindow().Options.GutterSize },
		Set: func(m action.Model, val any) {
			w := m.ActiveWindow()
			o := w.Options
			o.GutterSize = val.(int)
			w.SetOptions(o)
		},
	},
}

// lookupSetting: Finds a setting by name, short form, or prefix.
func lookupSetting(name string) *Setting {
	for i := range settingsMap {
		s := &settingsMap[i]
		if name == s.Name || name == s.ShortForm {
			return s
		}
		// Prefix matching
		if len(name) >= len(s.ShortForm) && strings.HasPrefix(s.Name, name) {
			return s
		}
	}
	return nil
}

// parseSetOption: Parses and applies a single :set option.
func parseSetOption(m action.Model, opt string) error {
	// Handle toggle: option!
	if name, ok := strings.CutSuffix(opt, "!"); ok {
		setting := lookupSetting(name)
		if setting != nil && setting.Type == BoolSetting {
			currentVal := setting.Get(m).(bool)
			setting.Set(m, !currentVal)
		}
		return nil
	}

	// Handle disable: nooption
	if name, ok := strings.CutPrefix(opt, "no"); ok {
		setting := lookupSetting(name)
		if setting != nil && setting.Type == BoolSetting {
			setting.Set(m, false)
		}
		return nil
	}

	// Handle assignment: option=value
	if strings.Contains(opt, "=") {
		parts := strings.SplitN(opt, "=", 2)
		name, value := parts[0], parts[1]

		setting := lookupSetting(name)
		if setting != nil {
			switch setting.Type {
			case IntSetting:
				intVal, err := strconv.Atoi(value)
				if err != nil {
					return err
				}
				setting.Set(m, intVal)
			case StringSetting:
				setting.Set(m, value)
			case BoolSetting:
				// Handle :set option=true / :set option=false
				boolVal := value == "true" || value == "1" || value == "yes"
				setting.Set(m, boolVal)
			}
		}
		return nil
	}

	// Handle enable: option (boolean only)
	setting := lookupSetting(opt)
	if setting != nil && setting.Type == BoolSetting {
		setting.Set(m, true)
	}

	return nil
}