Add route53 plugin (#1390)

* Update vendor

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add route53 plugin

This fix adds route53 plugin so that it is possible to
query route53 record through CoreDNS.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

vendor/github.com/jmespath/go-jmespath/util.go

@@ -0,0 +1,185 @@
+package jmespath
+
+import (
+	"errors"
+	"reflect"
+)
+
+// IsFalse determines if an object is false based on the JMESPath spec.
+// JMESPath defines false values to be any of:
+// - An empty string array, or hash.
+// - The boolean value false.
+// - nil
+func isFalse(value interface{}) bool {
+	switch v := value.(type) {
+	case bool:
+		return !v
+	case []interface{}:
+		return len(v) == 0
+	case map[string]interface{}:
+		return len(v) == 0
+	case string:
+		return len(v) == 0
+	case nil:
+		return true
+	}
+	// Try the reflection cases before returning false.
+	rv := reflect.ValueOf(value)
+	switch rv.Kind() {
+	case reflect.Struct:
+		// A struct type will never be false, even if
+		// all of its values are the zero type.
+		return false
+	case reflect.Slice, reflect.Map:
+		return rv.Len() == 0
+	case reflect.Ptr:
+		if rv.IsNil() {
+			return true
+		}
+		// If it's a pointer type, we'll try to deref the pointer
+		// and evaluate the pointer value for isFalse.
+		element := rv.Elem()
+		return isFalse(element.Interface())
+	}
+	return false
+}
+
+// ObjsEqual is a generic object equality check.
+// It will take two arbitrary objects and recursively determine
+// if they are equal.
+func objsEqual(left interface{}, right interface{}) bool {
+	return reflect.DeepEqual(left, right)
+}
+
+// SliceParam refers to a single part of a slice.
+// A slice consists of a start, a stop, and a step, similar to
+// python slices.
+type sliceParam struct {
+	N         int
+	Specified bool
+}
+
+// Slice supports [start:stop:step] style slicing that's supported in JMESPath.
+func slice(slice []interface{}, parts []sliceParam) ([]interface{}, error) {
+	computed, err := computeSliceParams(len(slice), parts)
+	if err != nil {
+		return nil, err
+	}
+	start, stop, step := computed[0], computed[1], computed[2]
+	result := []interface{}{}
+	if step > 0 {
+		for i := start; i < stop; i += step {
+			result = append(result, slice[i])
+		}
+	} else {
+		for i := start; i > stop; i += step {
+			result = append(result, slice[i])
+		}
+	}
+	return result, nil
+}
+
+func computeSliceParams(length int, parts []sliceParam) ([]int, error) {
+	var start, stop, step int
+	if !parts[2].Specified {
+		step = 1
+	} else if parts[2].N == 0 {
+		return nil, errors.New("Invalid slice, step cannot be 0")
+	} else {
+		step = parts[2].N
+	}
+	var stepValueNegative bool
+	if step < 0 {
+		stepValueNegative = true
+	} else {
+		stepValueNegative = false
+	}
+
+	if !parts[0].Specified {
+		if stepValueNegative {
+			start = length - 1
+		} else {
+			start = 0
+		}
+	} else {
+		start = capSlice(length, parts[0].N, step)
+	}
+
+	if !parts[1].Specified {
+		if stepValueNegative {
+			stop = -1
+		} else {
+			stop = length
+		}
+	} else {
+		stop = capSlice(length, parts[1].N, step)
+	}
+	return []int{start, stop, step}, nil
+}
+
+func capSlice(length int, actual int, step int) int {
+	if actual < 0 {
+		actual += length
+		if actual < 0 {
+			if step < 0 {
+				actual = -1
+			} else {
+				actual = 0
+			}
+		}
+	} else if actual >= length {
+		if step < 0 {
+			actual = length - 1
+		} else {
+			actual = length
+		}
+	}
+	return actual
+}
+
+// ToArrayNum converts an empty interface type to a slice of float64.
+// If any element in the array cannot be converted, then nil is returned
+// along with a second value of false.
+func toArrayNum(data interface{}) ([]float64, bool) {
+	// Is there a better way to do this with reflect?
+	if d, ok := data.([]interface{}); ok {
+		result := make([]float64, len(d))
+		for i, el := range d {
+			item, ok := el.(float64)
+			if !ok {
+				return nil, false
+			}
+			result[i] = item
+		}
+		return result, true
+	}
+	return nil, false
+}
+
+// ToArrayStr converts an empty interface type to a slice of strings.
+// If any element in the array cannot be converted, then nil is returned
+// along with a second value of false.  If the input data could be entirely
+// converted, then the converted data, along with a second value of true,
+// will be returned.
+func toArrayStr(data interface{}) ([]string, bool) {
+	// Is there a better way to do this with reflect?
+	if d, ok := data.([]interface{}); ok {
+		result := make([]string, len(d))
+		for i, el := range d {
+			item, ok := el.(string)
+			if !ok {
+				return nil, false
+			}
+			result[i] = item
+		}
+		return result, true
+	}
+	return nil, false
+}
+
+func isSliceType(v interface{}) bool {
+	if v == nil {
+		return false
+	}
+	return reflect.TypeOf(v).Kind() == reflect.Slice
+}