/*
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 zj.

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

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

package main

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

// 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`)

func main() {
	if err := run(os.Args[1:]); err != nil && err != errNoMoreOutput {
		os.Stderr.WriteString("\x1b[31m")
		os.Stderr.WriteString(err.Error())
		os.Stderr.WriteString("\x1b[0m\n")
		os.Exit(1)
	}
}

func run(keys []string) error {
	data, err := load(os.Stdin)
	if err != nil {
		return err
	}

	data, err = zoom(data, keys)
	if err != nil {
		return err
	}

	return output(os.Stdout, data)
}

// object is a map with ordered keys
type object struct {
	keys []string
	kv   map[string]any
}

func load(r io.Reader) (any, 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 nil, errors.New(`input has no JSON values`)
	}

	data, err := loadToken(dec, t)
	if err != nil {
		return nil, err
	}

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

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

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

func loadToken(dec *json.Decoder, t json.Token) (any, error) {
	switch t := t.(type) {
	case json.Delim:
		switch t {
		case json.Delim('['):
			return loadArray(dec)
		case json.Delim('{'):
			return loadObject(dec)
		default:
			return nil, errors.New(`unsupported JSON syntax`)
		}

	case nil:
		return nil, nil

	case bool:
		return t, nil

	case json.Number:
		return t, nil

	case string:
		return t, nil

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

func loadArray(dec *json.Decoder) ([]any, error) {
	var data []any

	for {
		t, err := dec.Token()
		if err == io.EOF {
			return data, nil
		}

		if err != nil {
			return data, err
		}

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

		v, err := loadToken(dec, t)
		if err != nil {
			return data, err
		}
		data = append(data, v)
	}
}

func loadObject(dec *json.Decoder) (object, error) {
	var data object
	data.kv = make(map[string]any)

	for {
		t, err := dec.Token()
		if err == io.EOF {
			return data, nil
		}

		if err != nil {
			return data, err
		}

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

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

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

		v, err := loadToken(dec, t)
		if err != nil {
			return data, err
		}

		if _, ok := data.kv[k]; !ok {
			data.keys = append(data.keys, k)
		}
		data.kv[k] = v
	}
}

var fallbackAliases = map[string]string{
	`.i`:    `.info`,
	`.k`:    `.keys`,
	`.l`:    `.length`,
	`.len`:  `.length`,
	`.t`:    `.type`,
	`.set`:  `.unique`,
	`.u`:    `.unique`,
	`.uniq`: `.unique`,
}

var fallbacks = map[string]func(v any, k string, rest []string) (any, error){
	`+`:       pick,
	`-`:       drop,
	`.keys`:   keys,
	`.info`:   info,
	`.length`: length,
	`.tally`:  tally,
	`.type`:   kind,
	`.unique`: unique,
}

func info(data any, k string, rest []string) (any, error) {
	switch data := data.(type) {
	case nil:
		return `null`, nil

	case bool:
		if data {
			return `true (boolean)`, nil
		}
		return `false (boolean)`, nil

	case json.Number:
		return data.String() + ` (number)`, nil

	case string:
		c := 0
		for range data {
			c++
		}
		return `string (` + strconv.Itoa(c) + ` runes)`, nil

	case []any:
		return `array (` + strconv.Itoa(len(data)) + ` items)`, nil

	case object:
		return `object (` + strconv.Itoa(len(data.keys)) + ` items)`, nil

	default:
		return ``, errors.New(`unsupported type`)
	}
}

func keys(data any, k string, rest []string) (any, error) {
	switch data := data.(type) {
	default:
		return nil, nil

	case string:
		c := 0
		for range data {
			c++
		}
		return c, nil

	case []any:
		keys := make([]any, 0, len(data))
		for i := range data {
			keys = append(keys, i)
		}
		return keys, nil

	case object:
		keys := make([]any, 0, len(data.keys))
		for _, k := range data.keys {
			keys = append(keys, k)
		}
		return keys, nil
	}
}

func length(data any, k string, rest []string) (any, error) {
	switch data := data.(type) {
	default:
		return nil, nil

	case string:
		c := 0
		for range data {
			c++
		}
		return c, nil

	case []any:
		return len(data), nil

	case object:
		return len(data.keys), nil
	}
}

func kind(data any, k string, rest []string) (any, error) {
	switch data.(type) {
	case nil:
		return `null`, nil
	case bool:
		return `boolean`, nil
	case int, json.Number:
		return `number`, nil
	case string:
		return `string`, nil
	case []any:
		return `array`, nil
	case object:
		return `object`, nil
	default:
		// return ``, errors.New(`unsupported type`)
		return fmt.Sprintf(`%T`, data), nil
	}
}

func tally(data any, k string, rest []string) (any, error) {
	switch data := data.(type) {
	default:
		return nil, nil
	case []any:
		return tallyArray(data), nil
	}
}

type tallySortable struct {
	keys  []string
	tally map[string]int
}

func (ts tallySortable) Len() int {
	return len(ts.keys)
}

func (ts tallySortable) Less(i, j int) bool {
	return ts.tally[ts.keys[i]] > ts.tally[ts.keys[j]]
}

func (ts tallySortable) Swap(i, j int) {
	ts.keys[i], ts.keys[j] = ts.keys[j], ts.keys[i]
}

func tallyArray(data []any) any {
	var keys []string
	tally := make(map[string]int)

	for _, v := range data {
		d, err := json.Marshal(v)
		if err != nil {
			continue
		}
		tag := string(d)

		if _, ok := tally[tag]; !ok {
			keys = append(keys, tag)
		}
		tally[tag]++
	}

	var sorted object
	sorted.kv = make(map[string]any)
	sort.Sort(tallySortable{keys: keys, tally: tally})
	for _, tag := range keys {
		sorted.keys = append(sorted.keys, tag)
		sorted.kv[tag] = tally[tag]
	}
	return sorted
}

func unique(data any, k string, rest []string) (any, error) {
	switch data := data.(type) {
	default:
		return data, nil
	case []any:
		return uniqueArray(data), nil
	}
}

func uniqueArray(data []any) any {
	var unique []any
	got := make(map[string]struct{})

	for _, v := range data {
		d, err := json.Marshal(v)
		if err != nil {
			continue
		}
		tag := string(d)

		if _, ok := got[tag]; ok {
			continue
		}

		unique = append(unique, v)
		got[tag] = struct{}{}
	}

	return unique
}

func pick(data any, k string, rest []string) (any, error) {
	switch data := data.(type) {
	case []any:
		return pickArray(data, rest)
	case object:
		return pickObject(data, rest), nil
	default:
		return nil, nil
	}
}

func drop(data any, k string, rest []string) (any, error) {
	switch data := data.(type) {
	case []any:
		return dropArray(data, rest)
	case object:
		return dropObject(data, uniqueStrings(rest)), nil
	default:
		return nil, nil
	}
}

func dealias(s string, aliases map[string]string) string {
	if alias, ok := aliases[s]; ok {
		return alias
	}
	return s
}

func zoom(data any, keys []string) (any, error) {
	for i, k := range keys {
		switch v := data.(type) {
		case []any:
			if i, ok := matchIndex(k, len(v)); ok {
				data = v[i]
				continue
			}

			if i, j, ok := matchSlice(k, len(v)); ok {
				if len(v) > 0 {
					data = v[i:j]
				}
				continue
			}

			if f, ok := fallbacks[dealias(k, fallbackAliases)]; ok {
				v, err := f(data, k, keys[i+1:])
				if err != nil {
					return v, err
				}
				data = v
				continue
			}

			// data = nil
			return data, errors.New(`arrays have no properties`)

		case object:
			if key, ok := matchKey(v, k); ok {
				data = v.kv[key]
				continue
			}

			if i, j, ok := matchSlice(k, len(v.keys)); ok {
				if len(v.keys) > 0 {
					v.keys = v.keys[i:j]
					data = v
				}
				continue
			}

			if f, ok := fallbacks[dealias(k, fallbackAliases)]; ok {
				v, err := f(data, k, keys[i+1:])
				if err != nil {
					return v, err
				}
				data = v
				continue
			}

			data = nil

		default:
			// return nil, errors.New(`can only zoom on arrays/objects`)
			data = nil
		}
	}

	return data, nil
}

func matchIndex(k string, length int) (int, bool) {
	if i, err := strconv.Atoi(k); err == nil {
		if i < 0 {
			i += length
		}

		if 0 <= i && i < length {
			return i, true
		}
	}

	return -1, false
}

func matchKey(data object, k string) (string, bool) {
	// try exact key-match
	if _, ok := data.kv[k]; ok {
		return k, true
	}

	// try a case-insensitive key-match
	for _, dk := range data.keys {
		if strings.EqualFold(k, dk) {
			return dk, true
		}
	}

	// try number-indexing
	if i, err := strconv.Atoi(k); err == nil {
		if i < 0 {
			i += len(data.keys)
		}

		if 0 <= i && i < len(data.keys) {
			return data.keys[i], true
		} else {
			return ``, false
		}
	}

	return ``, false
}

func matchSlice(k string, length int) (int, int, bool) {
	k = strings.TrimSpace(k)
	colon := strings.IndexByte(k, ':')

	// when there's no colon in it, key isn't a slice for sure
	if colon < 0 {
		return 0, 0, false
	}

	// can't slice an empty container
	if length == 0 {
		return 0, 0, false
	}

	// when given `:`
	if len(k) == 1 {
		return 0, length, true
	}

	// when slice starts with `:`, it implies starting from 0
	if colon == 0 {
		if end, ok := matchIndex(k[colon+1:], length); ok {
			return 0, end, true
		}
		return 0, 0, false
	}

	// when slice ends with `:`, it implies until the end
	if colon == len(k)-1 {
		if start, ok := matchIndex(k[:colon], length); ok {
			return start, length, true
		}
		return 0, 0, false
	}

	start, ok := matchIndex(k[:colon], length)
	if !ok {
		return 0, 0, false
	}

	end, ok := matchIndex(k[colon+1:], length)
	if !ok {
		return 0, 0, false
	}

	// backward/reversed slices aren't supported
	if start > end {
		return 0, 0, false
	}

	// restrict slices to valid ranges
	if start < 0 {
		start = 0
	}
	if end > length {
		end = length
	}
	return start, end, true
}

func pickArray(data []any, keys []string) ([]any, error) {
	var res []any
	for _, v := range data {
		if o, ok := v.(object); ok {
			res = append(res, pickObject(o, keys))
		}
	}
	return res, nil
}

func dropArray(data []any, keys []string) ([]any, error) {
	var res []any
	avoid := uniqueStrings(keys)
	for _, v := range data {
		if o, ok := v.(object); ok {
			res = append(res, dropObject(o, avoid))
		}
	}
	return res, nil
}

func pickObject(data object, keys []string) object {
	var o object
	o.kv = make(map[string]any)
	for _, k := range keys {
		if k, ok := matchKey(data, k); ok {
			o.keys = append(o.keys, k)
			o.kv[k] = data.kv[k]
		}
	}
	return o
}

func dropObject(data object, avoid map[string]struct{}) object {
	var o object
	o.kv = make(map[string]any)
	for _, k := range data.keys {
		if _, ok := avoid[k]; !ok {
			o.keys = append(o.keys, k)
			o.kv[k] = data.kv[k]
		}
	}
	return o
}

func uniqueStrings(values []string) map[string]struct{} {
	unique := make(map[string]struct{})
	for _, v := range values {
		unique[v] = struct{}{}
	}
	return unique
}

// escapedStringBytes helps func outputString 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},
}

// writeSpaces does what it says, minimizing calls to write-like funcs
func writeSpaces(w *bufio.Writer, n int) {
	const spaces = `                                `
	if n < 1 {
		return
	}

	for n >= len(spaces) {
		w.WriteString(spaces)
		n -= len(spaces)
	}
	w.WriteString(spaces[:n])
}

func output(w io.Writer, data any) error {
	bw := bufio.NewWriter(w)
	defer bw.Flush()

	if err := outputValue(bw, data, 0, 0); err != nil {
		return err
	}
	bw.WriteRune('\n')
	return nil
}

func outputValue(w *bufio.Writer, data any, pre, level int) error {
	switch data := data.(type) {
	case nil:
		w.WriteString(`null`)
		return nil

	case bool:
		if data {
			w.WriteString(`true`)
		} else {
			w.WriteString(`false`)
		}
		return nil

	case int:
		var buf [24]byte
		w.Write(strconv.AppendInt(buf[:0], int64(data), 10))
		return nil

	case json.Number:
		writeSpaces(w, 2*pre)
		w.WriteString(data.String())
		return nil

	case string:
		return outputString(w, data, pre)

	case []any:
		return outputArray(w, data, pre, level+1)

	case object:
		return outputObject(w, data, pre, level+1)

	default:
		return errors.New(`unexpected value type`)
	}
}

func outputArray(w *bufio.Writer, data []any, pre, level int) error {
	writeSpaces(w, 2*pre)
	w.WriteByte('[')

	for i, v := range data {
		if i > 0 {
			_, err := w.WriteString(",\n")
			if err != nil {
				return errNoMoreOutput
			}
		} else {
			w.WriteByte('\n')
		}

		if err := outputValue(w, v, level, level); err != nil {
			return err
		}
	}

	endComposite(len(data), w, level-1, ']')
	return nil
}

func outputObject(w *bufio.Writer, data object, pre, level int) error {
	writeSpaces(w, 2*pre)
	w.WriteByte('{')

	for i, k := range data.keys {
		if i > 0 {
			_, err := w.WriteString(",\n")
			if err != nil {
				return errNoMoreOutput
			}
		} else {
			w.WriteByte('\n')
		}

		if err := outputString(w, k, level); err != nil {
			return err
		}

		w.WriteString(": ")

		if err := outputValue(w, data.kv[k], 0, level); err != nil {
			return err
		}
	}

	endComposite(len(data.keys), w, pre, '}')
	return nil
}

func outputString(w *bufio.Writer, s string, level int) error {
	writeSpaces(w, 2*level)
	w.WriteByte('"')
	for i := range s {
		w.Write(escapedStringBytes[s[i]])
	}
	w.WriteByte('"')
	return nil
}

// endComposite handles common closing logic which is used twice both in each
// of func handleArray and func handleObject
func endComposite(i int, w *bufio.Writer, pre int, end byte) {
	if i > 0 {
		w.WriteByte('\n')
		writeSpaces(w, 2*pre)
	}
	w.WriteByte(end)
}