/*
Copyright 2020 The Kubernetes 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.
*/

// Copyright 2019 DeepMap, Inc.
//
// 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 runtime

import (
	"encoding/json"
	"fmt"
	"net/url"
	"reflect"
	"strings"
	"time"

	"github.com/pkg/errors"

	"k8s.io/autoscaler/cluster-autoscaler/cloudprovider/exoscale/internal/github.com/deepmap/oapi-codegen/pkg/types"
)

// This function binds a parameter as described in the Path Parameters
// section here to a Go object:
// https://swagger.io/docs/specification/serialization/
func BindStyledParameter(style string, explode bool, paramName string,
	value string, dest interface{}) error {

	if value == "" {
		return fmt.Errorf("parameter '%s' is empty, can't bind its value", paramName)
	}

	// Everything comes in by pointer, dereference it
	v := reflect.Indirect(reflect.ValueOf(dest))

	// This is the basic type of the destination object.
	t := v.Type()

	if t.Kind() == reflect.Struct {
		// We've got a destination object, we'll create a JSON representation
		// of the input value, and let the json library deal with the unmarshaling
		parts, err := splitStyledParameter(style, explode, true, paramName, value)
		if err != nil {
			return err
		}

		return bindSplitPartsToDestinationStruct(paramName, parts, explode, dest)
	}

	if t.Kind() == reflect.Slice {
		// Chop up the parameter into parts based on its style
		parts, err := splitStyledParameter(style, explode, false, paramName, value)
		if err != nil {
			return fmt.Errorf("error splitting input '%s' into parts: %s", value, err)
		}

		return bindSplitPartsToDestinationArray(parts, dest)
	}

	// Try to bind the remaining types as a base type.
	return BindStringToObject(value, dest)
}

// This is a complex set of operations, but each given parameter style can be
// packed together in multiple ways, using different styles of separators, and
// different packing strategies based on the explode flag. This function takes
// as input any parameter format, and unpacks it to a simple list of strings
// or key-values which we can then treat generically.
// Why, oh why, great Swagger gods, did you have to make this so complicated?
func splitStyledParameter(style string, explode bool, object bool, paramName string, value string) ([]string, error) {
	switch style {
	case "simple":
		// In the simple case, we always split on comma
		parts := strings.Split(value, ",")
		return parts, nil
	case "label":
		// In the label case, it's more tricky. In the no explode case, we have
		// /users/.3,4,5 for arrays
		// /users/.role,admin,firstName,Alex for objects
		// in the explode case, we have:
		// /users/.3.4.5
		// /users/.role=admin.firstName=Alex
		if explode {
			// In the exploded case, split everything on periods.
			parts := strings.Split(value, ".")
			// The first part should be an empty string because we have a
			// leading period.
			if parts[0] != "" {
				return nil, fmt.Errorf("invalid format for label parameter '%s', should start with '.'", paramName)
			}
			return parts[1:], nil

		} else {
			// In the unexploded case, we strip off the leading period.
			if value[0] != '.' {
				return nil, fmt.Errorf("invalid format for label parameter '%s', should start with '.'", paramName)
			}
			// The rest is comma separated.
			return strings.Split(value[1:], ","), nil
		}

	case "matrix":
		if explode {
			// In the exploded case, we break everything up on semicolon
			parts := strings.Split(value, ";")
			// The first part should always be empty string, since we started
			// with ;something
			if parts[0] != "" {
				return nil, fmt.Errorf("invalid format for matrix parameter '%s', should start with ';'", paramName)
			}
			parts = parts[1:]
			// Now, if we have an object, we just have a list of x=y statements.
			// for a non-object, like an array, we have id=x, id=y. id=z, etc,
			// so we need to strip the prefix from each of them.
			if !object {
				prefix := paramName + "="
				for i := range parts {
					parts[i] = strings.TrimPrefix(parts[i], prefix)
				}
			}
			return parts, nil
		} else {
			// In the unexploded case, parameters will start with ;paramName=
			prefix := ";" + paramName + "="
			if !strings.HasPrefix(value, prefix) {
				return nil, fmt.Errorf("expected parameter '%s' to start with %s", paramName, prefix)
			}
			str := strings.TrimPrefix(value, prefix)
			return strings.Split(str, ","), nil
		}
	case "form":
		var parts []string
		if explode {
			parts = strings.Split(value, "&")
			if !object {
				prefix := paramName + "="
				for i := range parts {
					parts[i] = strings.TrimPrefix(parts[i], prefix)
				}
			}
			return parts, nil
		} else {
			parts = strings.Split(value, ",")
			prefix := paramName + "="
			for i := range parts {
				parts[i] = strings.TrimPrefix(parts[i], prefix)
			}
		}
		return parts, nil
	}

	return nil, fmt.Errorf("unhandled parameter style: %s", style)
}

// Given a set of values as a slice, create a slice to hold them all, and
// assign to each one by one.
func bindSplitPartsToDestinationArray(parts []string, dest interface{}) error {
	// Everything comes in by pointer, dereference it
	v := reflect.Indirect(reflect.ValueOf(dest))

	// This is the basic type of the destination object.
	t := v.Type()

	// We've got a destination array, bind each object one by one.
	// This generates a slice of the correct element type and length to
	// hold all the parts.
	newArray := reflect.MakeSlice(t, len(parts), len(parts))
	for i, p := range parts {
		err := BindStringToObject(p, newArray.Index(i).Addr().Interface())
		if err != nil {
			return fmt.Errorf("error setting array element: %s", err)
		}
	}
	v.Set(newArray)
	return nil
}

// Given a set of chopped up parameter parts, bind them to a destination
// struct. The exploded parameter controls whether we send key value pairs
// in the exploded case, or a sequence of values which are interpreted as
// tuples.
// Given the struct Id { firstName string, role string }, as in the canonical
// swagger examples, in the exploded case, we would pass
// ["firstName=Alex", "role=admin"], where in the non-exploded case, we would
// pass "firstName", "Alex", "role", "admin"]
//
// We punt the hard work of binding these values to the object to the json
// library. We'll turn those arrays into JSON strings, and unmarshal
// into the struct.
func bindSplitPartsToDestinationStruct(paramName string, parts []string, explode bool, dest interface{}) error {
	// We've got a destination object, we'll create a JSON representation
	// of the input value, and let the json library deal with the unmarshaling
	var fields []string
	if explode {
		fields = make([]string, len(parts))
		for i, property := range parts {
			propertyParts := strings.Split(property, "=")
			if len(propertyParts) != 2 {
				return fmt.Errorf("parameter '%s' has invalid exploded format", paramName)
			}
			fields[i] = "\"" + propertyParts[0] + "\":\"" + propertyParts[1] + "\""
		}
	} else {
		if len(parts)%2 != 0 {
			return fmt.Errorf("parameter '%s' has invalid format, property/values need to be pairs", paramName)
		}
		fields = make([]string, len(parts)/2)
		for i := 0; i < len(parts); i += 2 {
			key := parts[i]
			value := parts[i+1]
			fields[i/2] = "\"" + key + "\":\"" + value + "\""
		}
	}
	jsonParam := "{" + strings.Join(fields, ",") + "}"
	err := json.Unmarshal([]byte(jsonParam), dest)
	if err != nil {
		return fmt.Errorf("error binding parameter %s fields: %s", paramName, err)
	}
	return nil
}

// This works much like BindStyledParameter, however it takes a query argument
// input array from the url package, since query arguments come through a
// different path than the styled arguments. They're also exceptionally fussy.
// For example, consider the exploded and unexploded form parameter examples:
// (exploded) /users?role=admin&firstName=Alex
// (unexploded) /users?id=role,admin,firstName,Alex
//
// In the first case, we can pull the "id" parameter off the context,
// and unmarshal via json as an intermediate. Easy. In the second case, we
// don't have the id QueryParam present, but must find "role", and "firstName".
// what if there is another parameter similar to "ID" named "role"? We can't
// tell them apart. This code tries to fail, but the moral of the story is that
// you shouldn't pass objects via form styled query arguments, just use
// the Content parameter form.
func BindQueryParameter(style string, explode bool, required bool, paramName string,
	queryParams url.Values, dest interface{}) error {

	// dv = destination value.
	dv := reflect.Indirect(reflect.ValueOf(dest))

	// intermediate value form which is either dv or dv dereferenced.
	v := dv

	// inner code will bind the string's value to this interface.
	var output interface{}

	if required {
		// If the parameter is required, then the generated code will pass us
		// a pointer to it: &int, &object, and so forth. We can directly set
		// them.
		output = dest
	} else {
		// For optional parameters, we have an extra indirect. An optional
		// parameter of type "int" will be *int on the struct. We pass that
		// in by pointer, and have **int.

		// If the destination, is a nil pointer, we need to allocate it.
		if v.IsNil() {
			t := v.Type()
			newValue := reflect.New(t.Elem())
			// for now, hang onto the output buffer separately from destination,
			// as we don't want to write anything to destination until we can
			// unmarshal successfully, and check whether a field is required.
			output = newValue.Interface()
		} else {
			// If the destination isn't nil, just use that.
			output = v.Interface()
		}

		// Get rid of that extra indirect as compared to the required case,
		// so the code below doesn't have to care.
		v = reflect.Indirect(reflect.ValueOf(output))
	}

	// This is the basic type of the destination object.
	t := v.Type()
	k := t.Kind()

	switch style {
	case "form":
		var parts []string
		if explode {
			// ok, the explode case in query arguments is very, very annoying,
			// because an exploded object, such as /users?role=admin&firstName=Alex
			// isn't actually present in the parameter array. We have to do
			// different things based on destination type.
			values, found := queryParams[paramName]
			var err error

			switch k {
			case reflect.Slice:
				// In the slice case, we simply use the arguments provided by
				// http library.
				if !found {
					if required {
						return fmt.Errorf("query parameter '%s' is required", paramName)
					} else {
						return nil
					}
				}
				err = bindSplitPartsToDestinationArray(values, output)
			case reflect.Struct:
				// This case is really annoying, and error prone, but the
				// form style object binding doesn't tell us which arguments
				// in the query string correspond to the object's fields. We'll
				// try to bind field by field.
				err = bindParamsToExplodedObject(paramName, queryParams, output)
			default:
				// Primitive object case. We expect to have 1 value to
				// unmarshal.
				if len(values) == 0 {
					if required {
						return fmt.Errorf("query parameter '%s' is required", paramName)
					} else {
						return nil
					}
				}
				if len(values) != 1 {
					return fmt.Errorf("multiple values for single value parameter '%s'", paramName)
				}
				err = BindStringToObject(values[0], output)
			}
			if err != nil {
				return err
			}
			// If the parameter is required, and we've successfully unmarshaled
			// it, this assigns the new object to the pointer pointer.
			if !required {
				dv.Set(reflect.ValueOf(output))
			}
			return nil
		} else {
			values, found := queryParams[paramName]
			if !found {
				if required {
					return fmt.Errorf("query parameter '%s' is required", paramName)
				} else {
					return nil
				}
			}
			if len(values) != 1 {
				return fmt.Errorf("parameter '%s' is not exploded, but is specified multiple times", paramName)
			}
			parts = strings.Split(values[0], ",")
		}
		var err error
		switch k {
		case reflect.Slice:
			err = bindSplitPartsToDestinationArray(parts, output)
		case reflect.Struct:
			err = bindSplitPartsToDestinationStruct(paramName, parts, explode, output)
		default:
			if len(parts) == 0 {
				if required {
					return fmt.Errorf("query parameter '%s' is required", paramName)
				} else {
					return nil
				}
			}
			if len(parts) != 1 {
				return fmt.Errorf("multiple values for single value parameter '%s'", paramName)
			}
			err = BindStringToObject(parts[0], output)
		}
		if err != nil {
			return err
		}
		if !required {
			dv.Set(reflect.ValueOf(output))
		}
		return nil
	case "deepObject":
		if !explode {
			return errors.New("deepObjects must be exploded")
		}
		return UnmarshalDeepObject(dest, paramName, queryParams)
	case "spaceDelimited", "pipeDelimited":
		return fmt.Errorf("query arguments of style '%s' aren't yet supported", style)
	default:
		return fmt.Errorf("style '%s' on parameter '%s' is invalid", style, paramName)

	}
}

// This function reflects the destination structure, and pulls the value for
// each settable field from the given parameters map. This is to deal with the
// exploded form styled object which may occupy any number of parameter names.
// We don't try to be smart here, if the field exists as a query argument,
// set its value.
func bindParamsToExplodedObject(paramName string, values url.Values, dest interface{}) error {
	// special handling for custom types
	switch dest.(type) {
	case *types.Date:
		return BindStringToObject(values.Get(paramName), dest)
	case *time.Time:
		return BindStringToObject(values.Get(paramName), dest)

	}

	v := reflect.Indirect(reflect.ValueOf(dest))
	if v.Type().Kind() != reflect.Struct {
		return fmt.Errorf("unmarshaling query arg '%s' into wrong type", paramName)
	}

	t := v.Type()

	for i := 0; i < t.NumField(); i++ {
		fieldT := t.Field(i)

		// Skip unsettable fields, such as internal ones.
		if !v.Field(i).CanSet() {
			continue
		}

		// Find the json annotation on the field, and use the json specified
		// name if available, otherwise, just the field name.
		tag := fieldT.Tag.Get("json")
		fieldName := fieldT.Name
		if tag != "" {
			tagParts := strings.Split(tag, ",")
			name := tagParts[0]
			if name != "" {
				fieldName = name
			}
		}

		// At this point, we look up field name in the parameter list.
		fieldVal, found := values[fieldName]
		if found {
			if len(fieldVal) != 1 {
				return fmt.Errorf("field '%s' specified multiple times for param '%s'", fieldName, paramName)
			}
			err := BindStringToObject(fieldVal[0], v.Field(i).Addr().Interface())
			if err != nil {
				return fmt.Errorf("could not bind query arg '%s' to request object: %s'", paramName, err)
			}
		}
	}
	return nil
}
