/*
The MIT License (MIT)

Copyright © 2020-2025 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.
*/

/*
Single-file source-code for ngron.

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

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

package main

import (
	"bufio"
	"encoding/json"
	"errors"
	"io"
	"os"
	"strconv"
)

const info = `
ngron [options...] [filepath/URI...]


Nice GRON converts JSON data into 'grep'-friendly lines, similar to what
tool 'gron' (GRep jsON; https://github.com/tomnomnom/gron) does.

This tool uses nicer ANSI styles than the original, hence its name, but
can't convert its output back into JSON, unlike the latter.

Unlike the original 'gron', there's no sort-mode. When not given a named
source (filepath/URI) to read from, data are read from standard input.

Options, where leading double-dashes are also allowed:

    -h         show this help message
    -help      show this help message

    -m         monochrome (default), enables unstyled output-mode
    -c         color, enables ANSI-styled output-mode
    -color     enables ANSI-styled output-mode
`

// errNoMoreOutput is a generic dummy output-error, which is meant to be
// ultimately ignored, being just an excuse to quit the app immediately
// and successfully
var errNoMoreOutput = errors.New(`no more output`)

type emitConfig struct {
	path    func(w *bufio.Writer, path []any) error
	null    func(w *bufio.Writer) error
	boolean func(w *bufio.Writer, b bool) error
	number  func(w *bufio.Writer, n json.Number) error
	key     func(w *bufio.Writer, k string) error
	text    func(w *bufio.Writer, s string) error

	arrayDecl  string
	objectDecl string
}

var monochrome = emitConfig{
	path:    monoPath,
	null:    monoNull,
	boolean: monoBool,
	number:  monoNumber,
	key:     monoString,
	text:    monoString,

	arrayDecl:  `[]`,
	objectDecl: `{}`,
}

var styled = emitConfig{
	path:    styledPath,
	null:    styledNull,
	boolean: styledBool,
	number:  styledNumber,
	key:     styledString,
	text:    styledString,

	arrayDecl:  "\x1b[38;2;168;168;168m[]\x1b[0m",
	objectDecl: "\x1b[38;2;168;168;168m{}\x1b[0m",
}

var config = monochrome

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

	if len(args) > 0 {
		switch args[0] {
		case `-h`, `--h`, `-help`, `--help`:
			os.Stderr.WriteString(info[1:])
			return
		case `-m`, `--m`:
			config = monochrome
			args = args[1:]
		case `-c`, `--c`, `-color`, `--color`:
			config = styled
			args = args[1:]
		}
	}

	if len(args) > 2 {
		const msg = "\x1b[31mmultiple inputs not allowed\x1b[0m\n"
		os.Stderr.WriteString(msg)
		os.Exit(1)
	}

	// figure out whether input should come from a named file or from stdin
	path := `-`
	if len(args) > 0 {
		path = args[0]
	}

	err := handleInput(os.Stdout, path)
	if err != nil && err != io.EOF && err != errNoMoreOutput {
		os.Stderr.WriteString("\x1b[31m")
		os.Stderr.WriteString(err.Error())
		os.Stderr.WriteString("\x1b[0m\n")
		os.Exit(1)
	}
}

type handlerFunc func(*bufio.Writer, *json.Decoder, json.Token, []any) error

// handleInput simplifies control-flow for func main
func handleInput(w io.Writer, path string) error {
	if path == `-` {
		bw := bufio.NewWriter(w)
		defer bw.Flush()
		return run(bw, os.Stdin)
	}

	f, err := os.Open(path)
	if err != nil {
		// on windows, file-not-found error messages may mention `CreateFile`,
		// even when trying to open files in read-only mode
		return errors.New(`can't open file named ` + path)
	}
	defer f.Close()

	bw := bufio.NewWriter(w)
	defer bw.Flush()
	return run(bw, f)
}

// escapedStringBytes helps func handleString treat all string bytes quickly
// and correctly, using their officially-supported JSON escape sequences
//
// https://www.rfc-editor.org/rfc/rfc8259#section-7
var escapedStringBytes = [256][]byte{
	{'\\', 'u', '0', '0', '0', '0'}, {'\\', 'u', '0', '0', '0', '1'},
	{'\\', 'u', '0', '0', '0', '2'}, {'\\', 'u', '0', '0', '0', '3'},
	{'\\', 'u', '0', '0', '0', '4'}, {'\\', 'u', '0', '0', '0', '5'},
	{'\\', 'u', '0', '0', '0', '6'}, {'\\', 'u', '0', '0', '0', '7'},
	{'\\', 'b'}, {'\\', 't'},
	{'\\', 'n'}, {'\\', 'u', '0', '0', '0', 'b'},
	{'\\', 'f'}, {'\\', 'r'},
	{'\\', 'u', '0', '0', '0', 'e'}, {'\\', 'u', '0', '0', '0', 'f'},
	{'\\', 'u', '0', '0', '1', '0'}, {'\\', 'u', '0', '0', '1', '1'},
	{'\\', 'u', '0', '0', '1', '2'}, {'\\', 'u', '0', '0', '1', '3'},
	{'\\', 'u', '0', '0', '1', '4'}, {'\\', 'u', '0', '0', '1', '5'},
	{'\\', 'u', '0', '0', '1', '6'}, {'\\', 'u', '0', '0', '1', '7'},
	{'\\', 'u', '0', '0', '1', '8'}, {'\\', 'u', '0', '0', '1', '9'},
	{'\\', 'u', '0', '0', '1', 'a'}, {'\\', 'u', '0', '0', '1', 'b'},
	{'\\', 'u', '0', '0', '1', 'c'}, {'\\', 'u', '0', '0', '1', 'd'},
	{'\\', 'u', '0', '0', '1', 'e'}, {'\\', 'u', '0', '0', '1', 'f'},
	{32}, {33}, {'\\', '"'}, {35}, {36}, {37}, {38}, {39},
	{40}, {41}, {42}, {43}, {44}, {45}, {46}, {47},
	{48}, {49}, {50}, {51}, {52}, {53}, {54}, {55},
	{56}, {57}, {58}, {59}, {60}, {61}, {62}, {63},
	{64}, {65}, {66}, {67}, {68}, {69}, {70}, {71},
	{72}, {73}, {74}, {75}, {76}, {77}, {78}, {79},
	{80}, {81}, {82}, {83}, {84}, {85}, {86}, {87},
	{88}, {89}, {90}, {91}, {'\\', '\\'}, {93}, {94}, {95},
	{96}, {97}, {98}, {99}, {100}, {101}, {102}, {103},
	{104}, {105}, {106}, {107}, {108}, {109}, {110}, {111},
	{112}, {113}, {114}, {115}, {116}, {117}, {118}, {119},
	{120}, {121}, {122}, {123}, {124}, {125}, {126}, {127},
	{128}, {129}, {130}, {131}, {132}, {133}, {134}, {135},
	{136}, {137}, {138}, {139}, {140}, {141}, {142}, {143},
	{144}, {145}, {146}, {147}, {148}, {149}, {150}, {151},
	{152}, {153}, {154}, {155}, {156}, {157}, {158}, {159},
	{160}, {161}, {162}, {163}, {164}, {165}, {166}, {167},
	{168}, {169}, {170}, {171}, {172}, {173}, {174}, {175},
	{176}, {177}, {178}, {179}, {180}, {181}, {182}, {183},
	{184}, {185}, {186}, {187}, {188}, {189}, {190}, {191},
	{192}, {193}, {194}, {195}, {196}, {197}, {198}, {199},
	{200}, {201}, {202}, {203}, {204}, {205}, {206}, {207},
	{208}, {209}, {210}, {211}, {212}, {213}, {214}, {215},
	{216}, {217}, {218}, {219}, {220}, {221}, {222}, {223},
	{224}, {225}, {226}, {227}, {228}, {229}, {230}, {231},
	{232}, {233}, {234}, {235}, {236}, {237}, {238}, {239},
	{240}, {241}, {242}, {243}, {244}, {245}, {246}, {247},
	{248}, {249}, {250}, {251}, {252}, {253}, {254}, {255},
}

// run does it all, given a reader and a writer
func run(w *bufio.Writer, r io.Reader) error {
	dec := json.NewDecoder(r)
	// avoid parsing numbers, so unusually-long numbers are kept verbatim,
	// even if JSON parsers aren't required to guarantee such input-fidelity
	// for numbers
	dec.UseNumber()

	t, err := dec.Token()
	if err == io.EOF {
		return errors.New(`input has no JSON values`)
	}

	if err = handleToken(w, dec, t, make([]any, 0, 50)); err != nil {
		return err
	}

	_, err = dec.Token()
	if err == io.EOF {
		// input is over, so it's a success
		return nil
	}

	if err == nil {
		// a successful `read` is a failure, as it means there are
		// trailing JSON tokens
		return errors.New(`unexpected trailing data`)
	}

	// any other error, perhaps some invalid-JSON-syntax-type error
	return err
}

// handleToken handles recursion for func run
func handleToken(w *bufio.Writer, dec *json.Decoder, t json.Token, path []any) error {
	switch t := t.(type) {
	case json.Delim:
		switch t {
		case json.Delim('['):
			return handleArray(w, dec, path)
		case json.Delim('{'):
			return handleObject(w, dec, path)
		default:
			return errors.New(`unsupported JSON syntax ` + string(t))
		}

	case nil:
		config.path(w, path)
		config.null(w)
		return endLine(w)

	case bool:
		config.path(w, path)
		config.boolean(w, t)
		return endLine(w)

	case json.Number:
		config.path(w, path)
		config.number(w, t)
		return endLine(w)

	case string:
		config.path(w, path)
		config.text(w, t)
		return endLine(w)

	default:
		// return fmt.Errorf(`unsupported token type %T`, t)
		return errors.New(`invalid JSON token`)
	}
}

// handleArray handles arrays for func handleToken
func handleArray(w *bufio.Writer, dec *json.Decoder, path []any) error {
	config.path(w, path)
	w.WriteString(config.arrayDecl)
	if err := endLine(w); err != nil {
		return err
	}

	path = append(path, 0)
	last := len(path) - 1

	for i := 0; true; i++ {
		path[last] = i

		t, err := dec.Token()
		if err != nil {
			return err
		}

		if t == json.Delim(']') {
			return nil
		}

		err = handleToken(w, dec, t, path)
		if err != nil {
			return err
		}
	}

	// make the compiler happy
	return nil
}

// handleObject handles objects for func handleToken
func handleObject(w *bufio.Writer, dec *json.Decoder, path []any) error {
	config.path(w, path)
	w.WriteString(config.objectDecl)
	if err := endLine(w); err != nil {
		return err
	}

	path = append(path, ``)
	last := len(path) - 1

	for i := 0; true; i++ {
		t, err := dec.Token()
		if err != nil {
			return err
		}

		if t == json.Delim('}') {
			return nil
		}

		k, ok := t.(string)
		if !ok {
			return errors.New(`expected a string for a key-value pair`)
		}

		path[last] = k
		if err != nil {
			return err
		}

		t, err = dec.Token()
		if err == io.EOF {
			return errors.New(`expected a value for a key-value pair`)
		}

		err = handleToken(w, dec, t, path)
		if err != nil {
			return err
		}
	}

	// make the compiler happy
	return nil
}

func monoPath(w *bufio.Writer, path []any) error {
	var buf [24]byte

	w.WriteString(`json`)

	for _, v := range path {
		switch v := v.(type) {
		case int:
			w.WriteByte('[')
			w.Write(strconv.AppendInt(buf[:0], int64(v), 10))
			w.WriteByte(']')

		case string:
			if !needsEscaping(v) {
				w.WriteByte('.')
				w.WriteString(v)
				continue
			}
			w.WriteByte('[')
			monoString(w, v)
			w.WriteByte(']')
		}
	}

	w.WriteString(` = `)
	return nil
}

func monoNull(w *bufio.Writer) error {
	w.WriteString(`null`)
	return nil
}

func monoBool(w *bufio.Writer, b bool) error {
	if b {
		w.WriteString(`true`)
	} else {
		w.WriteString(`false`)
	}
	return nil
}

func monoNumber(w *bufio.Writer, n json.Number) error {
	w.WriteString(n.String())
	return nil
}

func monoString(w *bufio.Writer, s string) error {
	w.WriteByte('"')
	for i := range s {
		w.Write(escapedStringBytes[s[i]])
	}
	w.WriteByte('"')
	return nil
}

func styledPath(w *bufio.Writer, path []any) error {
	var buf [24]byte

	w.WriteString("\x1b[38;2;135;95;255mjson\x1b[0m")

	for _, v := range path {
		switch v := v.(type) {
		case int:
			w.WriteString("\x1b[38;2;168;168;168m[")
			w.WriteString("\x1b[38;2;0;135;95m")
			w.Write(strconv.AppendInt(buf[:0], int64(v), 10))
			w.WriteString("\x1b[38;2;168;168;168m]\x1b[0m")

		case string:
			if !needsEscaping(v) {
				w.WriteString("\x1b[38;2;168;168;168m.")
				w.WriteString("\x1b[38;2;135;95;255m")
				w.WriteString(v)
				w.WriteString("\x1b[0m")
				continue
			}

			w.WriteString("\x1b[38;2;168;168;168m[")
			styledString(w, v)
			w.WriteString("\x1b[38;2;168;168;168m]\x1b[0m")
		}
	}

	w.WriteString(" \x1b[38;2;168;168;168m=\x1b[0m ")
	return nil
}

func styledNull(w *bufio.Writer) error {
	w.WriteString("\x1b[38;2;168;168;168m")
	w.WriteString(`null`)
	w.WriteString("\x1b[0m")
	return nil
}

func styledBool(w *bufio.Writer, b bool) error {
	if b {
		w.WriteString("\x1b[38;2;95;175;215mtrue\x1b[0m")
	} else {
		w.WriteString("\x1b[38;2;95;175;215mfalse\x1b[0m")
	}
	return nil
}

func styledNumber(w *bufio.Writer, n json.Number) error {
	w.WriteString("\x1b[38;2;0;135;95m")
	w.WriteString(n.String())
	w.WriteString("\x1b[0m")
	return nil
}

func styledString(w *bufio.Writer, s string) error {
	w.WriteString("\x1b[38;2;168;168;168m\"\x1b[0m")
	for i := range s {
		w.Write(escapedStringBytes[s[i]])
	}
	w.WriteString("\x1b[38;2;168;168;168m\"\x1b[0m")
	return nil
}

func needsEscaping(s string) bool {
	for _, r := range s {
		if r < ' ' || r > '~' {
			return true
		}

		switch r {
		case '\t', '\r', '\n', '\v', '"', '\\':
			return true
		}
	}

	return false
}

func endLine(w *bufio.Writer) error {
	w.WriteByte(';')
	if err := w.WriteByte('\n'); err != nil {
		return errNoMoreOutput
	}
	return nil
}