package dsl

import (
	"reflect"
	"regexp"
	"strconv"

	"goa.design/goa/v3/eval"
	"goa.design/goa/v3/expr"
)

const (
	// FormatDate describes RFC3339 date values.
	FormatDate = expr.FormatDate

	// FormatDateTime describes RFC3339 date time values.
	FormatDateTime = expr.FormatDateTime

	// FormatUUID describes RFC4122 UUID values.
	FormatUUID = expr.FormatUUID

	// FormatEmail describes RFC5322 email addresses.
	FormatEmail = expr.FormatEmail

	// FormatHostname describes RFC1035 Internet hostnames.
	FormatHostname = expr.FormatHostname

	// FormatIPv4 describes RFC2373 IPv4 address values.
	FormatIPv4 = expr.FormatIPv4

	// FormatIPv6 describes RFC2373 IPv6 address values.
	FormatIPv6 = expr.FormatIPv6

	// FormatIP describes RFC2373 IPv4 or IPv6 address values.
	FormatIP = expr.FormatIP

	// FormatURI describes RFC3986 URI values.
	FormatURI = expr.FormatURI

	// FormatMAC describes IEEE 802 MAC-48, EUI-48 or EUI-64 MAC address values.
	FormatMAC = expr.FormatMAC

	// FormatCIDR describes RFC4632 and RFC4291 CIDR notation IP address values.
	FormatCIDR = expr.FormatCIDR

	// FormatRegexp describes regular expression syntax accepted by RE2.
	FormatRegexp = expr.FormatRegexp

	// FormatJSON describes JSON text.
	FormatJSON = expr.FormatJSON

	// FormatRFC1123 describes RFC1123 date time values.
	FormatRFC1123 = expr.FormatRFC1123
)

// Enum adds a "enum" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor76.
//
// Example:
//
//    Attribute("string", String, func() {
//        Enum("this", "that", "and this")
//    })
//
//    Attribute("array", ArrayOf(Int), func() {
//        Elem(func() {
//            Enum(1, 2, 3, 4, 5)  // Sets possible values for array elements
//        })
//    })
//
func Enum(vals ...interface{}) {
	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
		for i, v := range vals {
			// When can a.Type be nil? glad you asked
			// There are two ways to write an Attribute declaration with the DSL that
			// don't set the type: with one argument - just the name - in which case the type
			// is set to String or with two arguments - the name and DSL. In this latter form
			// the type can end up being either String - if the DSL does not define any
			// attribute - or object if it does.
			// Why allowing this? because it's not always possible to specify the type of an
			// object - an object may just be declared inline to represent a substructure.
			// OK then why not assuming object and not allowing for string? because the DSL
			// where there's only one argument and the type is string implicitly is very
			// useful and common, for example to list attributes that refer to other attributes
			// such as responses that refer to responses defined at the API level or links that
			// refer to the result type attributes. So if the form that takes a DSL always ended
			// up defining an object we'd have a weird situation where one arg is string and
			// two args is object. Breaks the least surprise principle. Soooo long story
			// short the lesser evil seems to be to allow the ambiguity. Also tests like the
			// one below are really a convenience to the user and not a fundamental feature
			// - not checking in the case the type is not known yet is OK.
			if a.Type != nil && !a.Type.IsCompatible(v) {
				eval.ReportError("value %#v at index %d is incompatible with attribute of type %s",
					v, i, a.Type.Name())
				ok = false
			}
		}
		if ok {
			if a.Validation == nil {
				a.Validation = &expr.ValidationExpr{}
			}
			a.Validation.Values = make([]interface{}, len(vals))
			for i, v := range vals {
				switch actual := v.(type) {
				case expr.MapVal:
					a.Validation.Values[i] = actual.ToMap()
				case expr.ArrayVal:
					a.Validation.Values[i] = actual.ToSlice()
				default:
					a.Validation.Values[i] = actual
				}
			}
		}
	}
}

// Format adds a "format" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor104.
// The formats supported by goa are:
//
// FormatDate: RFC3339 date
//
// FormatDateTime: RFC3339 date time
//
// FormatUUID: RFC4122 uuid
//
// FormatEmail: RFC5322 email address
//
// FormatHostname: RFC1035 internet host name
//
// FormatIPv4, FormatIPv6, FormatIP: RFC2373 IPv4, IPv6 address or either
//
// FormatURI: RFC3986 URI
//
// FormatMAC: IEEE 802 MAC-48, EUI-48 or EUI-64 MAC address
//
// FormatCIDR: RFC4632 or RFC4291 CIDR notation IP address
//
// FormatRegexp: RE2 regular expression
//
// FormatJSON: JSON text
//
// FormatRFC1123: RFC1123 date time
//
// Example:
//
//    Attribute("created_at", String, func() {
//        Format(FormatDateTime)
//    })
func Format(f expr.ValidationFormat) {
	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
		if !a.IsSupportedValidationFormat(f) {
			eval.ReportError("invalid validation format %q", f)
		}
		if a.Type != nil && a.Type.Kind() != expr.StringKind {
			incompatibleAttributeType("format", a.Type.Name(), "a string")
		} else {
			if a.Validation == nil {
				a.Validation = &expr.ValidationExpr{}
			}
			a.Validation.Format = expr.ValidationFormat(f)
		}
	}
}

// Pattern adds a "pattern" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor33.
//
// Example:
//
//    Attribute("pattern", String, func() {
//        Pattern("^[A-Z].*[0-9]$")
//    })
//
func Pattern(p string) {
	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
		if a.Type != nil && a.Type.Kind() != expr.StringKind {
			incompatibleAttributeType("pattern", a.Type.Name(), "a string")
		} else {
			_, err := regexp.Compile(p)
			if err != nil {
				eval.ReportError("invalid pattern %#v, %s", p, err)
			} else {
				if a.Validation == nil {
					a.Validation = &expr.ValidationExpr{}
				}
				a.Validation.Pattern = p
			}
		}
	}
}

// Minimum adds a "minimum" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor21.
//
// Example:
//
//    Attribute("integer", Int, func() {
//        Minimum(100)
//    })
//
func Minimum(val interface{}) {
	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
		if a.Type != nil &&
			a.Type.Kind() != expr.IntKind && a.Type.Kind() != expr.UIntKind &&
			a.Type.Kind() != expr.Int32Kind && a.Type.Kind() != expr.UInt32Kind &&
			a.Type.Kind() != expr.Int64Kind && a.Type.Kind() != expr.UInt64Kind &&
			a.Type.Kind() != expr.Float32Kind && a.Type.Kind() != expr.Float64Kind {

			incompatibleAttributeType("minimum", a.Type.Name(), "an integer or a number")
		} else {
			var f float64
			switch v := val.(type) {
			case float32, float64, int, int8, int16, int32, int64, uint8, uint16, uint32, uint64:
				f = reflect.ValueOf(v).Convert(reflect.TypeOf(float64(0.0))).Float()
			case string:
				var err error
				f, err = strconv.ParseFloat(v, 64)
				if err != nil {
					eval.ReportError("invalid number value %#v", v)
					return
				}
			default:
				eval.ReportError("invalid number value %#v", v)
				return
			}
			if a.Validation == nil {
				a.Validation = &expr.ValidationExpr{}
			}
			a.Validation.Minimum = &f
		}
	}
}

// Maximum adds a "maximum" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor17.
//
// Example:
//
//    Attribute("integer", Int, func() {
//        Maximum(100)
//    })
//
func Maximum(val interface{}) {
	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
		if a.Type != nil &&
			a.Type.Kind() != expr.IntKind && a.Type.Kind() != expr.UIntKind &&
			a.Type.Kind() != expr.Int32Kind && a.Type.Kind() != expr.UInt32Kind &&
			a.Type.Kind() != expr.Int64Kind && a.Type.Kind() != expr.UInt64Kind &&
			a.Type.Kind() != expr.Float32Kind && a.Type.Kind() != expr.Float64Kind {

			incompatibleAttributeType("maximum", a.Type.Name(), "an integer or a number")
		} else {
			var f float64
			switch v := val.(type) {
			case float32, float64, int, int8, int16, int32, int64, uint8, uint16, uint32, uint64:
				f = reflect.ValueOf(v).Convert(reflect.TypeOf(float64(0.0))).Float()
			case string:
				var err error
				f, err = strconv.ParseFloat(v, 64)
				if err != nil {
					eval.ReportError("invalid number value %#v", v)
					return
				}
			default:
				eval.ReportError("invalid number value %#v", v)
				return
			}
			if a.Validation == nil {
				a.Validation = &expr.ValidationExpr{}
			}
			a.Validation.Maximum = &f
		}
	}
}

// MinLength adds a "minItems" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor45.
//
// Example:
//
//    Attribute("map", MapOf(String, String), func() {
//        MinLength(10)      // min key-values in map
//        Key(func() {
//            MinLength(1)   // min length of map key
//        })
//        Elem(func() {
//            MinLength(5)   // min length of map elements
//        })
//    })
//
func MinLength(val int) {
	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
		if a.Type != nil {
			kind := a.Type.Kind()
			if kind != expr.BytesKind &&
				kind != expr.StringKind &&
				kind != expr.ArrayKind &&
				kind != expr.MapKind {

				incompatibleAttributeType("minimum length", a.Type.Name(), "a string or an array")
				return
			}
		}
		if a.Validation == nil {
			a.Validation = &expr.ValidationExpr{}
		}
		a.Validation.MinLength = &val
	}
}

// MaxLength adds a "maxItems" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor42.
//
// Example:
//
//    Attribute("array", ArrayOf(String), func() {
//        MaxLength(200)    // max array length
//        Elem(func() {
//            MaxLength(5)  // max length of each array element
//        })
//    })
//
func MaxLength(val int) {
	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
		if a.Type != nil {
			kind := a.Type.Kind()
			if kind != expr.BytesKind &&
				kind != expr.StringKind &&
				kind != expr.ArrayKind &&
				kind != expr.MapKind {

				incompatibleAttributeType("maximum length", a.Type.Name(), "a string or an array")
				return
			}
		}
		if a.Validation == nil {
			a.Validation = &expr.ValidationExpr{}
		}
		a.Validation.MaxLength = &val
	}
}

// Required adds a "required" validation to the attribute.
// See http://json-schema.org/latest/json-schema-validation.html#anchor61.
//
// Example:
//
//    var _ = Type("MyType", func() {
//        Attribute("string", String)
//        Attribute("int", Integer)
//        Required("string", "int")
//    })
//
func Required(names ...string) {
	var at *expr.AttributeExpr

	switch def := eval.Current().(type) {
	case *expr.AttributeExpr:
		at = def
	case *expr.ResultTypeExpr:
		at = def.AttributeExpr
	case *expr.MappedAttributeExpr:
		at = def.AttributeExpr
	default:
		eval.IncompatibleDSL()
		return
	}

	if at.Type != nil && !expr.IsObject(at.Type) {
		incompatibleAttributeType("required", at.Type.Name(), "an object")
	} else {
		if at.Validation == nil {
			at.Validation = &expr.ValidationExpr{}
		}
		at.Validation.AddRequired(names...)
	}
}

// incompatibleAttributeType reports an error for validations defined on
// incompatible attributes (e.g. max value on string).
func incompatibleAttributeType(validation, actual, expected string) {
	eval.ReportError("invalid %s validation definition: attribute must be %s (but type is %s)",
		validation, expected, actual)
}