package contract

import (
	"encoding/json"
	"errors"
	"fmt"
	"math"
	"reflect"
	"strconv"
	"strings"
	"unicode/utf8"

	"git.yuntuo.hk/k2safe/go-omni/openapi"
)

func applyRange(s *openapi.Schema, value string) error {
	if len(value) < 3 || (value[0] != '[' && value[0] != '(') || (value[len(value)-1] != ']' && value[len(value)-1] != ')') {
		return errors.New("invalid range: use [min:max], (min:max), or mixed bounds")
	}
	lo, hi, ok := strings.Cut(value[1:len(value)-1], ":")
	if !ok || (lo == "" && hi == "") {
		return errors.New("invalid numeric range")
	}
	if lo != "" {
		v, err := bound(lo)
		if err != nil {
			return err
		}
		if s.Minimum == nil || v > *s.Minimum || (v == *s.Minimum && value[0] == '(') {
			s.Minimum = &v
			s.ExclusiveMinimum = value[0] == '('
		}
	}
	if hi != "" {
		v, err := bound(hi)
		if err != nil {
			return err
		}
		if s.Maximum == nil || v < *s.Maximum || (v == *s.Maximum && value[len(value)-1] == ')') {
			s.Maximum = &v
			s.ExclusiveMaximum = value[len(value)-1] == ')'
		}
	}
	return checkBounds(s)
}
func bound(s string) (float64, error) {
	v, err := strconv.ParseFloat(s, 64)
	if err != nil || math.IsInf(v, 0) || math.IsNaN(v) || math.Abs(v) > 1<<53 {
		return 0, errors.New("constraint bound must be finite and within ±2^53")
	}
	return v, nil
}
func checkBounds(s *openapi.Schema) error {
	if s.Minimum != nil && s.Maximum != nil && (*s.Minimum > *s.Maximum || (*s.Minimum == *s.Maximum && (s.ExclusiveMinimum || s.ExclusiveMaximum))) {
		return errors.New("empty numeric range")
	}
	if s.MinLength != nil && s.MaxLength != nil && *s.MinLength > *s.MaxLength {
		return errors.New("empty string length range")
	}
	if s.MinItems != nil && s.MaxItems != nil && *s.MinItems > *s.MaxItems {
		return errors.New("empty array length range")
	}
	return nil
}
func applyBinding(f *field) error {
	if f.binding == "" {
		return nil
	}
	n := base(f.value)
	k := n.typ.Kind()
	s := f.value.schema
	seen := map[string]bool{}
	for _, rule := range strings.Split(f.binding, ",") {
		name, value, _ := strings.Cut(rule, "=")
		if seen[name] {
			return fmt.Errorf("duplicate binding rule %s", name)
		}
		seen[name] = true
		switch name {
		case "required":
			if rule != name || f.optional || f.hasDefault {
				return errors.New("required conflicts with optional/default")
			}
			if !isScalar(k) {
				return errors.New("binding required supports scalars; other fields are already required by presence")
			}
			s.Nullable = false
			switch k {
			case reflect.String:
				one := 1
				s.MinLength = &one
			case reflect.Bool:
				s.Not = &openapi.Schema{Enum: []any{false}}
			default:
				s.Not = &openapi.Schema{Enum: []any{0}}
			}
		case "email":
			if rule != name || k != reflect.String {
				return errors.New("email requires a string")
			}
			s.Format = "email"
		case "min", "max", "len":
			if k == reflect.String || k == reflect.Slice {
				v, err := strconv.Atoi(value)
				if err != nil || v < 0 {
					return errors.New("length constraints must be nonnegative integers")
				}
				if k == reflect.String {
					if name == "min" || name == "len" {
						if s.MinLength == nil || v > *s.MinLength {
							s.MinLength = &v
						}
					}
					if name == "max" || name == "len" {
						s.MaxLength = &v
					}
				} else {
					if name == "min" || name == "len" {
						s.MinItems = &v
					}
					if name == "max" || name == "len" {
						s.MaxItems = &v
					}
				}
			} else if isNumber(k) && name != "len" {
				v, err := bound(value)
				if err != nil {
					return err
				}
				if name == "min" {
					if s.Minimum == nil || v > *s.Minimum {
						s.Minimum = &v
						s.ExclusiveMinimum = false
					}
				} else {
					if s.Maximum == nil || v < *s.Maximum {
						s.Maximum = &v
						s.ExclusiveMaximum = false
					}
				}
			} else {
				return fmt.Errorf("%s requires a number, string or slice", name)
			}
		default:
			return fmt.Errorf("unsupported binding rule %q; use required,min,max,len,email or source-tag options/range", name)
		}
	}
	return checkBounds(s)
}

func parseScalar(raw string, t reflect.Type) (any, error) {
	switch t.Kind() {
	case reflect.String:
		return raw, nil
	case reflect.Bool:
		if raw == "true" {
			return true, nil
		}
		if raw == "false" {
			return false, nil
		}
		return nil, errors.New("expected true or false")
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		v, err := strconv.ParseInt(raw, 10, t.Bits())
		if err != nil {
			return nil, errors.New("invalid integer")
		}
		return json.Number(strconv.FormatInt(v, 10)), nil
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		v, err := strconv.ParseUint(raw, 10, t.Bits())
		if err != nil {
			return nil, errors.New("invalid unsigned integer")
		}
		return json.Number(strconv.FormatUint(v, 10)), nil
	case reflect.Float32, reflect.Float64:
		v, err := strconv.ParseFloat(raw, t.Bits())
		if err != nil || math.IsInf(v, 0) || math.IsNaN(v) {
			return nil, errors.New("invalid finite number")
		}
		return json.Number(strconv.FormatFloat(v, 'g', -1, t.Bits())), nil
	}
	return nil, errors.New("expected scalar")
}

func checkField(f field, v reflect.Value) error {
	if v.Kind() == reflect.Pointer {
		if v.IsNil() {
			if strings.Contains(","+f.binding+",", ",required,") {
				return errors.New("must not be null")
			}
			return nil
		}
		v = v.Elem()
	}
	if strings.Contains(","+f.binding+",", ",required,") && v.IsZero() {
		return errors.New("must not be zero or empty")
	}
	s := f.value.schema
	if s.Format == "email" && valuesValidator.Var(v.Interface(), "email") != nil {
		return errors.New("invalid email")
	}
	if len(s.Enum) > 0 {
		found := false
		for _, item := range s.Enum {
			option := reflect.New(v.Type()).Elem()
			if setValue(base(f.value), option, item) == nil && reflect.DeepEqual(option.Interface(), v.Interface()) {
				found = true
				break
			}
		}
		if !found {
			return errors.New("not an allowed option")
		}
	}
	if isNumber(v.Kind()) {
		var number float64
		switch v.Kind() {
		case reflect.Float32, reflect.Float64:
			number = v.Float()
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			number = float64(v.Uint())
			if v.Uint() > 1<<53 {
				number = math.Inf(1)
			}
		default:
			number = float64(v.Int())
			if v.Int() > 1<<53 {
				number = math.Inf(1)
			} else if v.Int() < -(1 << 53) {
				number = math.Inf(-1)
			}
		}
		if s.Minimum != nil && (number < *s.Minimum || (s.ExclusiveMinimum && number == *s.Minimum)) {
			return errors.New("below minimum")
		}
		if s.Maximum != nil && (number > *s.Maximum || (s.ExclusiveMaximum && number == *s.Maximum)) {
			return errors.New("above maximum")
		}
	}
	if v.Kind() == reflect.String {
		size := utf8.RuneCountInString(v.String())
		if s.MinLength != nil && size < *s.MinLength {
			return errors.New("string too short")
		}
		if s.MaxLength != nil && size > *s.MaxLength {
			return errors.New("string too long")
		}
	}
	if v.Kind() == reflect.Slice {
		size := v.Len()
		if s.MinItems != nil && size < *s.MinItems {
			return errors.New("too few items")
		}
		if s.MaxItems != nil && size > *s.MaxItems {
			return errors.New("too many items")
		}
	}
	return nil
}