/*
Copyright The Helm Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package strvals

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"strconv"
	"strings"
	"unicode"

	"sigs.k8s.io/yaml"
)

// ErrNotList indicates that a non-list was treated as a list.
var ErrNotList = errors.New("not a list")

// MaxIndex is the maximum index that will be allowed by setIndex.
// The default value 65536 = 1024 * 64
var MaxIndex = 65536

// MaxNestedNameLevel is the maximum level of nesting for a value name that
// will be allowed.
var MaxNestedNameLevel = 30

// ToYAML takes a string of arguments and converts to a YAML document.
func ToYAML(s string) (string, error) {
	m, err := Parse(s)
	if err != nil {
		return "", err
	}
	d, err := yaml.Marshal(m)
	return strings.TrimSuffix(string(d), "\n"), err
}

// Parse parses a set line.
//
// A set line is of the form name1=value1,name2=value2
func Parse(s string) (map[string]any, error) {
	vals := map[string]any{}
	scanner := bytes.NewBufferString(s)
	t := newParser(scanner, vals, false)
	err := t.parse()
	return vals, err
}

// ParseString parses a set line and forces a string value.
//
// A set line is of the form name1=value1,name2=value2
func ParseString(s string) (map[string]any, error) {
	vals := map[string]any{}
	scanner := bytes.NewBufferString(s)
	t := newParser(scanner, vals, true)
	err := t.parse()
	return vals, err
}

// ParseInto parses a strvals line and merges the result into dest.
//
// If the strval string has a key that exists in dest, it overwrites the
// dest version.
func ParseInto(s string, dest map[string]any) error {
	scanner := bytes.NewBufferString(s)
	t := newParser(scanner, dest, false)
	return t.parse()
}

// ParseFile parses a set line, but its final value is loaded from the file at the path specified by the original value.
//
// A set line is of the form name1=path1,name2=path2
//
// When the files at path1 and path2 contained "val1" and "val2" respectively, the set line is consumed as
// name1=val1,name2=val2
func ParseFile(s string, reader RunesValueReader) (map[string]any, error) {
	vals := map[string]any{}
	scanner := bytes.NewBufferString(s)
	t := newFileParser(scanner, vals, reader)
	err := t.parse()
	return vals, err
}

// ParseIntoString parses a strvals line and merges the result into dest.
//
// This method always returns a string as the value.
func ParseIntoString(s string, dest map[string]any) error {
	scanner := bytes.NewBufferString(s)
	t := newParser(scanner, dest, true)
	return t.parse()
}

// ParseJSON parses a string with format key1=val1, key2=val2, ...
// where values are json strings (null, or scalars, or arrays, or objects).
// An empty val is treated as null.
//
// If a key exists in dest, the new value overwrites the dest version.
func ParseJSON(s string, dest map[string]any) error {
	scanner := bytes.NewBufferString(s)
	t := newJSONParser(scanner, dest)
	return t.parse()
}

// ParseIntoFile parses a filevals line and merges the result into dest.
//
// This method always returns a string as the value.
func ParseIntoFile(s string, dest map[string]any, reader RunesValueReader) error {
	scanner := bytes.NewBufferString(s)
	t := newFileParser(scanner, dest, reader)
	return t.parse()
}

// RunesValueReader is a function that takes the given value (a slice of runes)
// and returns the parsed value
type RunesValueReader func([]rune) (any, error)

// parser is a simple parser that takes a strvals line and parses it into a
// map representation.
//
// where sc is the source of the original data being parsed
// where data is the final parsed data from the parses with correct types
type parser struct {
	sc        *bytes.Buffer
	data      map[string]any
	reader    RunesValueReader
	isjsonval bool
}

func newParser(sc *bytes.Buffer, data map[string]any, stringBool bool) *parser {
	stringConverter := func(rs []rune) (any, error) {
		return typedVal(rs, stringBool), nil
	}
	return &parser{sc: sc, data: data, reader: stringConverter}
}

func newJSONParser(sc *bytes.Buffer, data map[string]any) *parser {
	return &parser{sc: sc, data: data, reader: nil, isjsonval: true}
}

func newFileParser(sc *bytes.Buffer, data map[string]any, reader RunesValueReader) *parser {
	return &parser{sc: sc, data: data, reader: reader}
}

func (t *parser) parse() error {
	for {
		err := t.key(t.data, 0)
		if err == nil {
			continue
		}
		if errors.Is(err, io.EOF) {
			return nil
		}
		return err
	}
}

func runeSet(r []rune) map[rune]bool {
	s := make(map[rune]bool, len(r))
	for _, rr := range r {
		s[rr] = true
	}
	return s
}

func (t *parser) key(data map[string]any, nestedNameLevel int) (reterr error) {
	defer func() {
		if r := recover(); r != nil {
			reterr = fmt.Errorf("unable to parse key: %s", r)
		}
	}()
	stop := runeSet([]rune{'=', '[', ',', '.'})
	for {
		switch k, last, err := runesUntil(t.sc, stop); {
		case err != nil:
			if len(k) == 0 {
				return err
			}
			return fmt.Errorf("key %q has no value", string(k))
			//set(data, string(k), "")
			//return err
		case last == '[':
			// We are in a list index context, so we need to set an index.
			i, err := t.keyIndex()
			if err != nil {
				return fmt.Errorf("error parsing index: %w", err)
			}
			kk := string(k)
			// Find or create target list
			list := []any{}
			if _, ok := data[kk]; ok {
				list = data[kk].([]any)
			}

			// Now we need to get the value after the ].
			list, err = t.listItem(list, i, nestedNameLevel)
			set(data, kk, list)
			return err
		case last == '=':
			if t.isjsonval {
				empval, err := t.emptyVal()
				if err != nil {
					return err
				}
				if empval {
					set(data, string(k), nil)
					return nil
				}
				// parse jsonvals by using Go’s JSON standard library
				// Decode is preferred to Unmarshal in order to parse just the json parts of the list key1=jsonval1,key2=jsonval2,...
				// Since Decode has its own buffer that consumes more characters (from underlying t.sc) than the ones actually decoded,
				// we invoke Decode on a separate reader built with a copy of what is left in t.sc. After Decode is executed, we
				// discard in t.sc the chars of the decoded json value (the number of those characters is returned by InputOffset).
				var jsonval any
				dec := json.NewDecoder(strings.NewReader(t.sc.String()))
				if err = dec.Decode(&jsonval); err != nil {
					return err
				}
				set(data, string(k), jsonval)
				if _, err = io.CopyN(io.Discard, t.sc, dec.InputOffset()); err != nil {
					return err
				}
				// skip possible blanks and comma
				_, err = t.emptyVal()
				return err
			}
			// End of key. Consume =, Get value.
			// FIXME: Get value list first
			vl, e := t.valList()
			switch e {
			case nil:
				set(data, string(k), vl)
				return nil
			case io.EOF:
				set(data, string(k), "")
				return e
			case ErrNotList:
				rs, e := t.val()
				if e != nil && e != io.EOF {
					return e
				}
				v, e := t.reader(rs)
				set(data, string(k), v)
				return e
			default:
				return e
			}
		case last == ',':
			// No value given. Set the value to empty string. Return error.
			set(data, string(k), "")
			return fmt.Errorf("key %q has no value (cannot end with ,)", string(k))
		case last == '.':
			// Check value name is within the maximum nested name level
			nestedNameLevel++
			if nestedNameLevel > MaxNestedNameLevel {
				return fmt.Errorf("value name nested level is greater than maximum supported nested level of %d", MaxNestedNameLevel)
			}

			// First, create or find the target map.
			inner := map[string]any{}
			if _, ok := data[string(k)]; ok {
				inner = data[string(k)].(map[string]any)
			}

			// Recurse
			e := t.key(inner, nestedNameLevel)
			if e == nil && len(inner) == 0 {
				return fmt.Errorf("key map %q has no value", string(k))
			}
			if len(inner) != 0 {
				set(data, string(k), inner)
			}
			return e
		}
	}
}

func set(data map[string]any, key string, val any) {
	// If key is empty, don't set it.
	if len(key) == 0 {
		return
	}
	data[key] = val
}

func setIndex(list []any, index int, val any) (l2 []any, err error) {
	// There are possible index values that are out of range on a target system
	// causing a panic. This will catch the panic and return an error instead.
	// The value of the index that causes a panic varies from system to system.
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("error processing index %d: %s", index, r)
		}
	}()

	if index < 0 {
		return list, fmt.Errorf("negative %d index not allowed", index)
	}
	if index > MaxIndex {
		return list, fmt.Errorf("index of %d is greater than maximum supported index of %d", index, MaxIndex)
	}
	if len(list) <= index {
		newlist := make([]any, index+1)
		copy(newlist, list)
		list = newlist
	}
	list[index] = val
	return list, nil
}

func (t *parser) keyIndex() (int, error) {
	// First, get the key.
	stop := runeSet([]rune{']'})
	v, _, err := runesUntil(t.sc, stop)
	if err != nil {
		return 0, err
	}
	// v should be the index
	return strconv.Atoi(string(v))

}

func (t *parser) listItem(list []any, i, nestedNameLevel int) ([]any, error) {
	if i < 0 {
		return list, fmt.Errorf("negative %d index not allowed", i)
	}
	stop := runeSet([]rune{'[', '.', '='})
	switch k, last, err := runesUntil(t.sc, stop); {
	case len(k) > 0:
		return list, fmt.Errorf("unexpected data at end of array index: %q", k)
	case err != nil:
		return list, err
	case last == '=':
		if t.isjsonval {
			empval, err := t.emptyVal()
			if err != nil {
				return list, err
			}
			if empval {
				return setIndex(list, i, nil)
			}
			// parse jsonvals by using Go’s JSON standard library
			// Decode is preferred to Unmarshal in order to parse just the json parts of the list key1=jsonval1,key2=jsonval2,...
			// Since Decode has its own buffer that consumes more characters (from underlying t.sc) than the ones actually decoded,
			// we invoke Decode on a separate reader built with a copy of what is left in t.sc. After Decode is executed, we
			// discard in t.sc the chars of the decoded json value (the number of those characters is returned by InputOffset).
			var jsonval any
			dec := json.NewDecoder(strings.NewReader(t.sc.String()))
			if err = dec.Decode(&jsonval); err != nil {
				return list, err
			}
			if list, err = setIndex(list, i, jsonval); err != nil {
				return list, err
			}
			if _, err = io.CopyN(io.Discard, t.sc, dec.InputOffset()); err != nil {
				return list, err
			}
			// skip possible blanks and comma
			_, err = t.emptyVal()
			return list, err
		}
		vl, e := t.valList()
		switch e {
		case nil:
			return setIndex(list, i, vl)
		case io.EOF:
			return setIndex(list, i, "")
		case ErrNotList:
			rs, e := t.val()
			if e != nil && e != io.EOF {
				return list, e
			}
			v, e := t.reader(rs)
			if e != nil {
				return list, e
			}
			return setIndex(list, i, v)
		default:
			return list, e
		}
	case last == '[':
		// now we have a nested list. Read the index and handle.
		nextI, err := t.keyIndex()
		if err != nil {
			return list, fmt.Errorf("error parsing index: %w", err)
		}
		var crtList []any
		if len(list) > i {
			// If nested list already exists, take the value of list to next cycle.
			existed := list[i]
			if existed != nil {
				crtList = list[i].([]any)
			}
		}
		// Now we need to get the value after the ].
		list2, err := t.listItem(crtList, nextI, nestedNameLevel)
		if err != nil {
			return list, err
		}
		return setIndex(list, i, list2)
	case last == '.':
		// We have a nested object. Send to t.key
		inner := map[string]any{}
		if len(list) > i {
			var ok bool
			inner, ok = list[i].(map[string]any)
			if !ok {
				// We have indices out of order. Initialize empty value.
				list[i] = map[string]any{}
				inner = list[i].(map[string]any)
			}
		}

		// Recurse
		e := t.key(inner, nestedNameLevel)
		if e != nil {
			return list, e
		}
		return setIndex(list, i, inner)
	default:
		return nil, fmt.Errorf("parse error: unexpected token %v", last)
	}
}

// check for an empty value
// read and consume optional spaces until comma or EOF (empty val) or any other char (not empty val)
// comma and spaces are consumed, while any other char is not consumed
func (t *parser) emptyVal() (bool, error) {
	for {
		r, _, e := t.sc.ReadRune()
		if e == io.EOF {
			return true, nil
		}
		if e != nil {
			return false, e
		}
		if r == ',' {
			return true, nil
		}
		if !unicode.IsSpace(r) {
			t.sc.UnreadRune()
			return false, nil
		}
	}
}

func (t *parser) val() ([]rune, error) {
	stop := runeSet([]rune{','})
	v, _, err := runesUntil(t.sc, stop)
	return v, err
}

func (t *parser) valList() ([]any, error) {
	r, _, e := t.sc.ReadRune()
	if e != nil {
		return []any{}, e
	}

	if r != '{' {
		t.sc.UnreadRune()
		return []any{}, ErrNotList
	}

	list := []any{}
	stop := runeSet([]rune{',', '}'})
	for {
		switch rs, last, err := runesUntil(t.sc, stop); {
		case err != nil:
			if err == io.EOF {
				err = errors.New("list must terminate with '}'")
			}
			return list, err
		case last == '}':
			// If this is followed by ',', consume it.
			if r, _, e := t.sc.ReadRune(); e == nil && r != ',' {
				t.sc.UnreadRune()
			}
			v, e := t.reader(rs)
			list = append(list, v)
			return list, e
		case last == ',':
			v, e := t.reader(rs)
			if e != nil {
				return list, e
			}
			list = append(list, v)
		}
	}
}

func runesUntil(in io.RuneReader, stop map[rune]bool) ([]rune, rune, error) {
	v := []rune{}
	for {
		switch r, _, e := in.ReadRune(); {
		case e != nil:
			return v, r, e
		case inMap(r, stop):
			return v, r, nil
		case r == '\\':
			next, _, e := in.ReadRune()
			if e != nil {
				return v, next, e
			}
			v = append(v, next)
		default:
			v = append(v, r)
		}
	}
}

func inMap(k rune, m map[rune]bool) bool {
	_, ok := m[k]
	return ok
}

func typedVal(v []rune, st bool) any {
	val := string(v)

	if st {
		return val
	}

	if strings.EqualFold(val, "true") {
		return true
	}

	if strings.EqualFold(val, "false") {
		return false
	}

	if strings.EqualFold(val, "null") {
		return nil
	}

	if strings.EqualFold(val, "0") {
		return int64(0)
	}

	// If this value does not start with zero, try parsing it to an int
	if len(val) != 0 && val[0] != '0' {
		if iv, err := strconv.ParseInt(val, 10, 64); err == nil {
			return iv
		}
	}

	return val
}
