/*
The MIT License (MIT)

Copyright (c) 2026 pacman64

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/*
To compile a smaller-sized command-line app, you can use the `go` command as
follows:

go build -ldflags "-s -w" -trimpath ecoli.go
*/

package main

import (
	"bufio"
	"io"
	"os"
	"regexp"
)

const info = `
ecoli [options...] [regex/style pairs...]


Expressions COloring LInes tries to match each line read from the standard
input to the regexes given, coloring/styling with the named-style paired
to the first matching regex, if any. Lines not matching any regex stay the
same.

The options are, available both in single and double-dash versions

    -h, -help                 show this help message
    -i, -ins, -insensitive    match the regexes given case-insensitively

Some of the colors/styles available are:

    blue         blueback
    bold
    gray         grayback
    green        greenback
    inverse
    magenta      magentaback
    orange       orangeback
    purple       purpleback
    red          redback
    underline

Some style aliases are:

    b       blue                  bb       blueback
    g       green                 gb       greenback
    m       magenta               mb       magentaback
    o       orange                ob       orangeback
    p       purple                pb       purpleback
    r       red                   rb       redback
    i       inverse (highlight)
    u       underline
`

var styleAliases = map[string]string{
	`b`: `blue`,
	`g`: `green`,
	`m`: `magenta`,
	`o`: `orange`,
	`p`: `purple`,
	`r`: `red`,
	`u`: `underline`,

	`bb`: `blueback`,
	`bg`: `greenback`,
	`bm`: `magentaback`,
	`bo`: `orangeback`,
	`bp`: `purpleback`,
	`br`: `redback`,

	`gb`: `greenback`,
	`mb`: `magentaback`,
	`ob`: `orangeback`,
	`pb`: `purpleback`,
	`rb`: `redback`,

	`hi`:  `inverse`,
	`inv`: `inverse`,
	`mag`: `magenta`,

	`du`: `doubleunderline`,

	`flip`: `inverse`,
	`swap`: `inverse`,

	`reset`:     `plain`,
	`highlight`: `inverse`,
	`hilite`:    `inverse`,
	`invert`:    `inverse`,
	`inverted`:  `inverse`,
	`swapped`:   `inverse`,

	`dunderline`:  `doubleunderline`,
	`dunderlined`: `doubleunderline`,

	`strikethrough`: `strike`,
	`strikethru`:    `strike`,
	`struck`:        `strike`,

	`underlined`: `underline`,

	`bblue`:    `blueback`,
	`bgray`:    `grayback`,
	`bgreen`:   `greenback`,
	`bmagenta`: `magentaback`,
	`borange`:  `orangeback`,
	`bpurple`:  `purpleback`,
	`bred`:     `redback`,

	`bgblue`:    `blueback`,
	`bggray`:    `grayback`,
	`bggreen`:   `greenback`,
	`bgmag`:     `magentaback`,
	`bgmagenta`: `magentaback`,
	`bgorange`:  `orangeback`,
	`bgpurple`:  `purpleback`,
	`bgred`:     `redback`,

	`bluebg`:    `blueback`,
	`graybg`:    `grayback`,
	`greenbg`:   `greenback`,
	`magbg`:     `magentaback`,
	`magentabg`: `magentaback`,
	`orangebg`:  `orangeback`,
	`purplebg`:  `purpleback`,
	`redbg`:     `redback`,

	`backblue`:    `blueback`,
	`backgray`:    `grayback`,
	`backgreen`:   `greenback`,
	`backmag`:     `magentaback`,
	`backmagenta`: `magentaback`,
	`backorange`:  `orangeback`,
	`backpurple`:  `purpleback`,
	`backred`:     `redback`,
}

var styles = map[string]string{
	`blue`:            "\x1b[38;2;0;95;215m",
	`bold`:            "\x1b[1m",
	`doubleunderline`: "\x1b[21m",
	`gray`:            "\x1b[38;2;168;168;168m",
	`green`:           "\x1b[38;2;0;135;95m",
	`inverse`:         "\x1b[7m",
	`magenta`:         "\x1b[38;2;215;0;255m",
	`orange`:          "\x1b[38;2;215;95;0m",
	`plain`:           "\x1b[0m",
	`purple`:          "\x1b[38;2;135;95;255m",
	`red`:             "\x1b[38;2;204;0;0m",
	`strike`:          "\x1b[9m",
	`underline`:       "\x1b[4m",

	`blueback`:    "\x1b[48;2;0;95;215m\x1b[38;2;238;238;238m",
	`grayback`:    "\x1b[48;2;168;168;168m\x1b[38;2;238;238;238m",
	`greenback`:   "\x1b[48;2;0;135;95m\x1b[38;2;238;238;238m",
	`magentaback`: "\x1b[48;2;215;0;255m\x1b[38;2;238;238;238m",
	`orangeback`:  "\x1b[48;2;215;95;0m\x1b[38;2;238;238;238m",
	`purpleback`:  "\x1b[48;2;135;95;255m\x1b[38;2;238;238;238m",
	`redback`:     "\x1b[48;2;204;0;0m\x1b[38;2;238;238;238m",
}

// pair has a regular-expression and its associated ANSI-code style together
type pair struct {
	expr  *regexp.Regexp
	style string
}

func main() {
	buffered := false
	insensitive := false
	args := os.Args[1:]

out:
	for len(args) > 0 {
		switch args[0] {
		case `-b`, `--b`, `-buffered`, `--buffered`:
			buffered = true
			args = args[1:]
			continue

		case `-h`, `--h`, `-help`, `--help`:
			os.Stdout.WriteString(info[1:])
			return

		case `-i`, `--i`, `-ins`, `--ins`:
			insensitive = true
			args = args[1:]
			continue

		default:
			break out
		}
	}

	if len(args) > 0 && args[0] == `--` {
		args = args[1:]
	}

	if len(args)%2 != 0 {
		const msg = "you forgot the style-name for/after the last regex\n"
		os.Stderr.WriteString(msg)
		os.Exit(1)
	}

	nerr := 0
	pairs := make([]pair, 0, len(args)/2)

	for len(args) >= 2 {
		src := args[0]
		sname := args[1]

		var err error
		var exp *regexp.Regexp
		if insensitive {
			exp, err = regexp.Compile(`(?i)` + src)
		} else {
			exp, err = regexp.Compile(src)
		}
		if err != nil {
			os.Stderr.WriteString(err.Error())
			os.Stderr.WriteString("\n")
			nerr++
		}

		if alias, ok := styleAliases[sname]; ok {
			sname = alias
		}

		style, ok := styles[sname]
		if !ok {
			os.Stderr.WriteString("no style named `")
			os.Stderr.WriteString(args[1])
			os.Stderr.WriteString("`\n")
			nerr++
		}

		pairs = append(pairs, pair{expr: exp, style: style})
		args = args[2:]
	}

	if nerr > 0 {
		os.Exit(1)
	}

	liveLines := !buffered
	if !buffered {
		if _, err := os.Stdout.Seek(0, io.SeekCurrent); err == nil {
			liveLines = false
		}
	}

	sc := bufio.NewScanner(os.Stdin)
	sc.Buffer(nil, 8*1024*1024*1024)
	bw := bufio.NewWriter(os.Stdout)
	var plain []byte

	for i := 0; sc.Scan(); i++ {
		s := sc.Bytes()
		if i == 0 && len(s) > 2 && s[0] == 0xef && s[1] == 0xbb && s[2] == 0xbf {
			s = s[3:]
		}
		plain = appendPlain(plain[:0], s)

		if err := handleLine(bw, s, noANSI(plain), pairs); err != nil {
			return
		}

		if !liveLines {
			continue
		}

		if err := bw.Flush(); err != nil {
			return
		}
	}
}

// appendPlain extends the slice given using the non-ANSI parts of a string
func appendPlain(dst []byte, src []byte) []byte {
	for len(src) > 0 {
		i, j := indexEscapeSequence(src)
		if i < 0 {
			dst = append(dst, src...)
			break
		}
		if j < 0 {
			j = len(src)
		}

		if i > 0 {
			dst = append(dst, src[:i]...)
		}

		src = src[j:]
	}

	return dst
}

// indexEscapeSequence finds the first ANSI-style escape-sequence, which is
// the multi-byte sequences starting with ESC[; the result is a pair of slice
// indices which can be independently negative when either the start/end of
// a sequence isn't found; given their fairly-common use, even the hyperlink
// ESC]8 sequences are supported
func indexEscapeSequence(s []byte) (int, int) {
	var prev byte

	for i, b := range s {
		if prev == '\x1b' && b == '[' {
			j := indexLetter(s[i+1:])
			if j < 0 {
				return i, -1
			}
			return i - 1, i + 1 + j + 1
		}

		if prev == '\x1b' && b == ']' && i+1 < len(s) && s[i+1] == '8' {
			j := indexPair(s[i+1:], '\x1b', '\\')
			if j < 0 {
				return i, -1
			}
			return i - 1, i + 1 + j + 2
		}

		prev = b
	}

	return -1, -1
}

func indexLetter(s []byte) int {
	for i, b := range s {
		upper := b &^ 32
		if 'A' <= upper && upper <= 'Z' {
			return i
		}
	}

	return -1
}

func indexPair(s []byte, x byte, y byte) int {
	var prev byte

	for i, b := range s {
		if prev == x && b == y {
			return i
		}
		prev = b
	}

	return -1
}

// noANSI ensures arguments to func handleLine are given in the right order
type noANSI []byte

// handleLine styles the current line given to it using the first matching
// regex, keeping it as given if none of the regexes match; it's given 2
// strings: the first is the original line, the latter is its plain-text
// version (with no ANSI codes) and is used for the regex-matching, since
// ANSI codes use a mix of numbers and letters, which can themselves match
func handleLine(w *bufio.Writer, s []byte, plain noANSI, pairs []pair) error {
	for _, p := range pairs {
		if p.expr.Match(plain) {
			w.WriteString(p.style)
			w.Write(s)
			w.WriteString("\x1b[0m")
			return w.WriteByte('\n')
		}
	}

	w.Write(s)
	return w.WriteByte('\n')
}