package yaml

import (

	"encoding/base64"

	"math"

	"regexp"

	"strconv"

	"strings"

	"time"

)

type resolveMapItem struct {

	value interface{}

	tag   string

}

var resolveTable = make([]byte, 256)

var resolveMap = make(map[string]resolveMapItem)

func init() {

	t := resolveTable

	t[int('+')] = 'S' // Sign

	t[int('-')] = 'S'

	for _, c := range "0123456789" {

		t[int(c)] = 'D' // Digit

	}

	for _, c := range "yYnNtTfFoO~" {

		t[int(c)] = 'M' // In map

	}

	t[int('.')] = '.' // Float (potentially in map)

	var resolveMapList = []struct {

		v   interface{}

		tag string

		l   []string

	}{

		{true, yaml_BOOL_TAG, []string{"y", "Y", "yes", "Yes", "YES"}},

		{true, yaml_BOOL_TAG, []string{"true", "True", "TRUE"}},

		{true, yaml_BOOL_TAG, []string{"on", "On", "ON"}},

		{false, yaml_BOOL_TAG, []string{"n", "N", "no", "No", "NO"}},

		{false, yaml_BOOL_TAG, []string{"false", "False", "FALSE"}},

		{false, yaml_BOOL_TAG, []string{"off", "Off", "OFF"}},

		{nil, yaml_NULL_TAG, []string{"", "~", "null", "Null", "NULL"}},

		{math.NaN(), yaml_FLOAT_TAG, []string{".nan", ".NaN", ".NAN"}},

		{math.Inf(+1), yaml_FLOAT_TAG, []string{".inf", ".Inf", ".INF"}},

		{math.Inf(+1), yaml_FLOAT_TAG, []string{"+.inf", "+.Inf", "+.INF"}},

		{math.Inf(-1), yaml_FLOAT_TAG, []string{"-.inf", "-.Inf", "-.INF"}},

		{"<<", yaml_MERGE_TAG, []string{"<<"}},

	}

	m := resolveMap

	for _, item := range resolveMapList {

		for _, s := range item.l {

			m[s] = resolveMapItem{item.v, item.tag}

		}

	}

}

const longTagPrefix = "tag:yaml.org,2002:"

func shortTag(tag string) string {

	// TODO This can easily be made faster and produce less garbage.

	if strings.HasPrefix(tag, longTagPrefix) {

		return "!!" + tag[len(longTagPrefix):]

	}

	return tag

}

func longTag(tag string) string {

	if strings.HasPrefix(tag, "!!") {

		return longTagPrefix + tag[2:]

	}

	return tag

}

func resolvableTag(tag string) bool {

	switch tag {

	case "", yaml_STR_TAG, yaml_BOOL_TAG, yaml_INT_TAG, yaml_FLOAT_TAG, yaml_NULL_TAG, yaml_TIMESTAMP_TAG:

		return true

	}

	return false

}

var yamlStyleFloat = regexp.MustCompile(`^[-+]?(\.[0-9]+|[0-9]+(\.[0-9]*)?)([eE][-+]?[0-9]+)?$`)

func resolve(tag string, in string) (rtag string, out interface{}) {

	if !resolvableTag(tag) {

		return tag, in

	}

	defer func() {

		switch tag {

		case "", rtag, yaml_STR_TAG, yaml_BINARY_TAG:

			return

		case yaml_FLOAT_TAG:

			if rtag == yaml_INT_TAG {

				switch v := out.(type) {

				case int64:

					rtag = yaml_FLOAT_TAG

					out = float64(v)

					return

				case int:

					rtag = yaml_FLOAT_TAG

					out = float64(v)

					return

				}

			}

		}

		failf("cannot decode %s `%s` as a %s", shortTag(rtag), in, shortTag(tag))

	}()

	// Any data is accepted as a !!str or !!binary.

	// Otherwise, the prefix is enough of a hint about what it might be.

	hint := byte('N')

	if in != "" {

		hint = resolveTable[in[0]]

	}

	if hint != 0 && tag != yaml_STR_TAG && tag != yaml_BINARY_TAG {

		// Handle things we can lookup in a map.

		if item, ok := resolveMap[in]; ok {

			return item.tag, item.value

		}

		// Base 60 floats are a bad idea, were dropped in YAML 1.2, and

		// are purposefully unsupported here. They're still quoted on

		// the way out for compatibility with other parser, though.

		switch hint {

		case 'M':

			// We've already checked the map above.

		case '.':

			// Not in the map, so maybe a normal float.

			floatv, err := strconv.ParseFloat(in, 64)

			if err == nil {

				return yaml_FLOAT_TAG, floatv

			}

		case 'D', 'S':

			// Int, float, or timestamp.

			// Only try values as a timestamp if the value is unquoted or there's an explicit

			// !!timestamp tag.

			if tag == "" || tag == yaml_TIMESTAMP_TAG {

				t, ok := parseTimestamp(in)

				if ok {

					return yaml_TIMESTAMP_TAG, t

				}

			}

			plain := strings.Replace(in, "_", "", -1)

			intv, err := strconv.ParseInt(plain, 0, 64)

			if err == nil {

				if intv == int64(int(intv)) {

					return yaml_INT_TAG, int(intv)

				} else {

					return yaml_INT_TAG, intv

				}

			}

			uintv, err := strconv.ParseUint(plain, 0, 64)

			if err == nil {

				return yaml_INT_TAG, uintv

			}

			if yamlStyleFloat.MatchString(plain) {

				floatv, err := strconv.ParseFloat(plain, 64)

				if err == nil {

					return yaml_FLOAT_TAG, floatv

				}

			}

			if strings.HasPrefix(plain, "0b") {

				intv, err := strconv.ParseInt(plain[2:], 2, 64)

				if err == nil {

					if intv == int64(int(intv)) {

						return yaml_INT_TAG, int(intv)

					} else {

						return yaml_INT_TAG, intv

					}

				}

				uintv, err := strconv.ParseUint(plain[2:], 2, 64)

				if err == nil {

					return yaml_INT_TAG, uintv

				}

			} else if strings.HasPrefix(plain, "-0b") {

				intv, err := strconv.ParseInt("-" + plain[3:], 2, 64)

				if err == nil {

					if true || intv == int64(int(intv)) {

						return yaml_INT_TAG, int(intv)

					} else {

						return yaml_INT_TAG, intv

					}

				}

			}

		default:

			panic("resolveTable item not yet handled: " + string(rune(hint)) + " (with " + in + ")")

		}

	}

	return yaml_STR_TAG, in

}

// encodeBase64 encodes s as base64 that is broken up into multiple lines

// as appropriate for the resulting length.

func encodeBase64(s string) string {

	const lineLen = 70

	encLen := base64.StdEncoding.EncodedLen(len(s))

	lines := encLen/lineLen + 1

	buf := make([]byte, encLen*2+lines)

	in := buf[0:encLen]

	out := buf[encLen:]

	base64.StdEncoding.Encode(in, []byte(s))

	k := 0

	for i := 0; i < len(in); i += lineLen {

		j := i + lineLen

		if j > len(in) {

			j = len(in)

		}

		k += copy(out[k:], in[i:j])

		if lines > 1 {

			out[k] = '\n'

			k++

		}

	}

	return string(out[:k])

}

// This is a subset of the formats allowed by the regular expression

// defined at http://yaml.org/type/timestamp.html.

var allowedTimestampFormats = []string{

	"2006-1-2T15:4:5.999999999Z07:00", // RCF3339Nano with short date fields.

	"2006-1-2t15:4:5.999999999Z07:00", // RFC3339Nano with short date fields and lower-case "t".

	"2006-1-2 15:4:5.999999999",       // space separated with no time zone

	"2006-1-2",                        // date only

	// Notable exception: time.Parse cannot handle: "2001-12-14 21:59:43.10 -5"

	// from the set of examples.

}

// parseTimestamp parses s as a timestamp string and

// returns the timestamp and reports whether it succeeded.

// Timestamp formats are defined at http://yaml.org/type/timestamp.html

func parseTimestamp(s string) (time.Time, bool) {

	// TODO write code to check all the formats supported by

	// http://yaml.org/type/timestamp.html instead of using time.Parse.

	// Quick check: all date formats start with YYYY-.

	i := 0

	for ; i < len(s); i++ {

		if c := s[i]; c < '0' || c > '9' {

			break

		}

	}

	if i != 4 || i == len(s) || s[i] != '-' {

		return time.Time{}, false

	}

	for _, format := range allowedTimestampFormats {

		if t, err := time.Parse(format, s); err == nil {

			return t, true

		}

	}

	return time.Time{}, false

}