package logie

import (
	"fmt"
	"os"
	"strings"
	"time"
)

const (
	printFmt       = "%s%s %s\n"
	escape    byte = 0x1B
	csi       byte = '['
	separator byte = ';'
	csiEnd    byte = 'm'
	fgColor   byte = '3'
	bgColor   byte = '4'
	reset     byte = '0'
)

type Maybe[T any] struct {
	exists bool
	value  T
}

func Exists[T any](t T) Maybe[T] {
	return Maybe[T]{
		exists: true,
		value:  t,
	}
}

func Empty[T any]() Maybe[T] {
	return Maybe[T]{}
}

func (m Maybe[T]) Exists() bool {
	return m.exists
}

func (m Maybe[T]) Value() T {
	return m.value
}

type Color uint8

const (
	ColorBlack   = '0'
	ColorRed     = '1'
	ColorGreen   = '2'
	ColorYellow  = '3'
	ColorBlue    = '4'
	ColorMagenta = '5'
	ColorCyan    = '6'
	ColorWhite   = '7'
)

type ColorSet struct {
	fg   Maybe[Color]
	bg   Maybe[Color]
	font Maybe[Font]
}

func Colors() ColorSet {
	return ColorSet{}
}

func (c ColorSet) Foreground(fg Color) ColorSet {
	c.fg = Exists(fg)
	return c
}

func (c ColorSet) Background(bg Color) ColorSet {
	c.bg = Exists(bg)
	return c
}

func (c ColorSet) Font(f Font) ColorSet {
	c.font = Exists(f)
	return c
}

func (c ColorSet) String(v string) string {
	var hasFg, hasBg, hasFont = c.fg.Exists(), c.bg.Exists(), c.font.Exists()
	if !hasFg && !hasBg && !hasFont {
		return v
	}
	// Build format
	formatBytes := []byte{escape, csi}
	if hasFg {
		formatBytes = append(formatBytes, fgColor, byte(c.fg.Value()))
	}
	if hasBg {
		if len(formatBytes) > 2 {
			formatBytes = append(formatBytes, separator)
		}
		formatBytes = append(formatBytes, bgColor, byte(c.bg.Value()))
	}
	if hasFont {
		if len(formatBytes) > 2 {
			formatBytes = append(formatBytes, separator)
		}
		formatBytes = append(formatBytes, byte(c.font.Value()))
	}
	formatBytes = append(formatBytes, csiEnd)
	formatBytes = append(append(formatBytes, []byte(v)...), escape, csi, reset, csiEnd)
	return string(formatBytes)
}

type Font uint8

const (
	FontBold       = '1'
	FontFaint      = '2'
	FontUnderlined = '4'
	FontSlowBlink  = '5'
)

var (
	info   = Colors().Font(FontFaint).String("[INFO]")
	warn   = Colors().Background(ColorYellow).String("[WARN]")
	error_ = Colors().Foreground(ColorWhite).Background(ColorRed).Font(FontBold).String("[ERROR]")
	fatal  = Colors().Foreground(ColorRed).Background(ColorYellow).Font(FontBold).String("[FATAL]")
)

type Log struct {
	output    *os.File
	timeFmt   string
	color     map[int]ColorSet
	timeColor ColorSet
}

func New() Log {
	return Log{
		output:    os.Stdout,
		timeFmt:   time.RFC822,
		timeColor: Colors().Font(FontFaint),
		color:     map[int]ColorSet{},
	}
}

func (l Log) Clone() Log {
	colorClone := map[int]ColorSet{}
	for k, cs := range l.color {
		colorClone[k] = cs
	}
	l.color = colorClone
	return l
}

// ColorBracket returns a Log with the coloring information for the bracket index.
//
// The way coloring works in Logie is that you can only color the parts of your
// message that are within closed brackets `[]` in its format string
// (therefore non-f calls cannot color). The [index] being passed in is a zero-indexed
// index of which bracket set to color.
func (l Log) ColorBracket(index int, set ColorSet) Log {
	l = l.Clone()
	l.color[index] = set

	return l
}

func (l Log) time() string {
	return l.timeColor.String("[" + time.Now().Format(l.timeFmt) + "]")
}

func (l Log) Logf(level, format string, args ...any) {
	line := fmt.Sprintf(colorize(format, l.color), args...)
	fmt.Fprintf(l.output, printFmt, l.time(), level, line)
}

func colorize(format string, colors map[int]ColorSet) string {
	var (
		parts        = []string{}
		bracketParts = []int{}
		last         int
	)
outer:
	for index := 0; index < len(format); index++ {
		if format[index] == '[' {
			parts = append(parts, format[last:index])

			for inner := index + 1; index < len(format); inner++ {
				if format[inner] == ']' {
					current := format[index : inner+1]
					parts = append(parts, current)
					bracketParts = append(bracketParts, len(parts)-1)
					last = inner + 1
					continue outer
				}
			}

			parts = append(parts, format[index:])
		}
	}
	parts = append(parts, format[last:])

	for bracketIndex, color := range colors {
		if bracketIndex >= len(bracketParts) {
			continue
		}
		parts[bracketParts[bracketIndex]] = color.String(parts[bracketParts[bracketIndex]])
	}

	return strings.Join(parts, "")
}

func (l Log) Log(level string, args ...any) {
	line := fmt.Sprint(args...)
	fmt.Fprintf(l.output, printFmt, l.time(), level, line)
}

func (l Log) Infof(format string, args ...any) {
	l.Logf(info, format, args...)
}

func (l Log) Info(args ...any) {
	l.Log(info, args...)
}

func (l Log) Warnf(format string, args ...any) {
	l.Logf(warn, format, args...)
}

func (l Log) Warn(args ...any) {
	l.Log(warn, args...)
}

func (l Log) Errorf(format string, args ...any) {
	l.Logf(error_, format, args...)
}

func (l Log) Error(args ...any) {
	l.Log(error_, args...)
}

func (l Log) Fatalf(format string, args ...any) {
	l.Logf(fatal, format, args...)
	os.Exit(1)
}

func (l Log) Fatal(args ...any) {
	l.Log(fatal, args...)
	os.Exit(1)
}