// 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 codegen

import (
	"bufio"
	"bytes"
	"fmt"
	"strings"
	"text/template"
	"unicode"

	"github.com/getkin/kin-openapi/openapi3"
	"github.com/pkg/errors"
)

type ParameterDefinition struct {
	ParamName string // The original json parameter name, eg param_name
	In        string // Where the parameter is defined - path, header, cookie, query
	Required  bool   // Is this a required parameter?
	Spec      *openapi3.Parameter
	Schema    Schema
}

// This function is here as an adapter after a large refactoring so that I don't
// have to update all the templates. It returns the type definition for a parameter,
// without the leading '*' for optional ones.
func (pd ParameterDefinition) TypeDef() string {
	typeDecl := pd.Schema.TypeDecl()
	return typeDecl
}

// Generate the JSON annotation to map GoType to json type name. If Parameter
// Foo is marshaled to json as "foo", this will create the annotation
// 'json:"foo"'
func (pd *ParameterDefinition) JsonTag() string {
	if pd.Required {
		return fmt.Sprintf("`json:\"%s\"`", pd.ParamName)
	} else {
		return fmt.Sprintf("`json:\"%s,omitempty\"`", pd.ParamName)
	}
}

func (pd *ParameterDefinition) IsJson() bool {
	p := pd.Spec
	if len(p.Content) == 1 {
		_, found := p.Content["application/json"]
		return found
	}
	return false
}

func (pd *ParameterDefinition) IsPassThrough() bool {
	p := pd.Spec
	if len(p.Content) > 1 {
		return true
	}
	if len(p.Content) == 1 {
		return !pd.IsJson()
	}
	return false
}

func (pd *ParameterDefinition) IsStyled() bool {
	p := pd.Spec
	return p.Schema != nil
}

func (pd *ParameterDefinition) Style() string {
	style := pd.Spec.Style
	if style == "" {
		in := pd.Spec.In
		switch in {
		case "path", "header":
			return "simple"
		case "query", "cookie":
			return "form"
		default:
			panic("unknown parameter format")
		}
	}
	return style
}

func (pd *ParameterDefinition) Explode() bool {
	if pd.Spec.Explode == nil {
		in := pd.Spec.In
		switch in {
		case "path", "header":
			return false
		case "query", "cookie":
			return true
		default:
			panic("unknown parameter format")
		}
	}
	return *pd.Spec.Explode
}

func (pd ParameterDefinition) GoVariableName() string {
	name := LowercaseFirstCharacter(pd.GoName())
	if IsGoKeyword(name) {
		name = "p" + UppercaseFirstCharacter(name)
	}
	if unicode.IsNumber([]rune(name)[0]) {
		name = "n" + name
	}
	return name
}

func (pd ParameterDefinition) GoName() string {
	return ToCamelCase(pd.ParamName)
}

func (pd ParameterDefinition) IndirectOptional() bool {
	return !pd.Required && !pd.Schema.SkipOptionalPointer
}

type ParameterDefinitions []ParameterDefinition

func (p ParameterDefinitions) FindByName(name string) *ParameterDefinition {
	for _, param := range p {
		if param.ParamName == name {
			return &param
		}
	}
	return nil
}

// This function walks the given parameters dictionary, and generates the above
// descriptors into a flat list. This makes it a lot easier to traverse the
// data in the template engine.
func DescribeParameters(params openapi3.Parameters, path []string) ([]ParameterDefinition, error) {
	outParams := make([]ParameterDefinition, 0)
	for _, paramOrRef := range params {
		param := paramOrRef.Value

		goType, err := paramToGoType(param, append(path, param.Name))
		if err != nil {
			return nil, fmt.Errorf("error generating type for param (%s): %s",
				param.Name, err)
		}

		pd := ParameterDefinition{
			ParamName: param.Name,
			In:        param.In,
			Required:  param.Required,
			Spec:      param,
			Schema:    goType,
		}

		// If this is a reference to a predefined type, simply use the reference
		// name as the type. $ref: "#/components/schemas/custom_type" becomes
		// "CustomType".
		if paramOrRef.Ref != "" {
			goType, err := RefPathToGoType(paramOrRef.Ref)
			if err != nil {
				return nil, fmt.Errorf("error dereferencing (%s) for param (%s): %s",
					paramOrRef.Ref, param.Name, err)
			}
			pd.Schema.GoType = goType
		}
		outParams = append(outParams, pd)
	}
	return outParams, nil
}

type SecurityDefinition struct {
	ProviderName string
	Scopes       []string
}

func DescribeSecurityDefinition(securityRequirements openapi3.SecurityRequirements) []SecurityDefinition {
	outDefs := make([]SecurityDefinition, 0)

	for _, sr := range securityRequirements {
		for k, v := range sr {
			outDefs = append(outDefs, SecurityDefinition{ProviderName: k, Scopes: v})
		}
	}

	return outDefs
}

// This structure describes an Operation
type OperationDefinition struct {
	OperationId string // The operation_id description from Swagger, used to generate function names

	PathParams          []ParameterDefinition // Parameters in the path, eg, /path/:param
	HeaderParams        []ParameterDefinition // Parameters in HTTP headers
	QueryParams         []ParameterDefinition // Parameters in the query, /path?param
	CookieParams        []ParameterDefinition // Parameters in cookies
	TypeDefinitions     []TypeDefinition      // These are all the types we need to define for this operation
	SecurityDefinitions []SecurityDefinition  // These are the security providers
	BodyRequired        bool
	Bodies              []RequestBodyDefinition // The list of bodies for which to generate handlers.
	Summary             string                  // Summary string from Swagger, used to generate a comment
	Method              string                  // GET, POST, DELETE, etc.
	Path                string                  // The Swagger path for the operation, like /resource/{id}
	Spec                *openapi3.Operation
}

// Returns the list of all parameters except Path parameters. Path parameters
// are handled differently from the rest, since they're mandatory.
func (o *OperationDefinition) Params() []ParameterDefinition {
	result := append(o.QueryParams, o.HeaderParams...)
	result = append(result, o.CookieParams...)
	return result
}

// Returns all parameters
func (o *OperationDefinition) AllParams() []ParameterDefinition {
	result := append(o.QueryParams, o.HeaderParams...)
	result = append(result, o.CookieParams...)
	result = append(result, o.PathParams...)
	return result
}

// If we have parameters other than path parameters, they're bundled into an
// object. Returns true if we have any of those. This is used from the template
// engine.
func (o *OperationDefinition) RequiresParamObject() bool {
	return len(o.Params()) > 0
}

// This is called by the template engine to determine whether to generate body
// marshaling code on the client. This is true for all body types, whether or
// not we generate types for them.
func (o *OperationDefinition) HasBody() bool {
	return o.Spec.RequestBody != nil
}

// This returns the Operations summary as a multi line comment
func (o *OperationDefinition) SummaryAsComment() string {
	if o.Summary == "" {
		return ""
	}
	trimmed := strings.TrimSuffix(o.Summary, "\n")
	parts := strings.Split(trimmed, "\n")
	for i, p := range parts {
		parts[i] = "// " + p
	}
	return strings.Join(parts, "\n")
}

// Produces a list of type definitions for a given Operation for the response
// types which we know how to parse. These will be turned into fields on a
// response object for automatic deserialization of responses in the generated
// Client code. See "client-with-responses.tmpl".
func (o *OperationDefinition) GetResponseTypeDefinitions() ([]TypeDefinition, error) {
	var tds []TypeDefinition

	responses := o.Spec.Responses
	sortedResponsesKeys := SortedResponsesKeys(responses)
	for _, responseName := range sortedResponsesKeys {
		responseRef := responses[responseName]

		// We can only generate a type if we have a value:
		if responseRef.Value != nil {
			sortedContentKeys := SortedContentKeys(responseRef.Value.Content)
			for _, contentTypeName := range sortedContentKeys {
				contentType := responseRef.Value.Content[contentTypeName]
				// We can only generate a type if we have a schema:
				if contentType.Schema != nil {
					responseSchema, err := GenerateGoSchema(contentType.Schema, []string{responseName})
					if err != nil {
						return nil, errors.Wrap(err, fmt.Sprintf("Unable to determine Go type for %s.%s", o.OperationId, contentTypeName))
					}

					var typeName string
					switch {
					case StringInArray(contentTypeName, contentTypesJSON):
						typeName = fmt.Sprintf("JSON%s", ToCamelCase(responseName))
					// YAML:
					case StringInArray(contentTypeName, contentTypesYAML):
						typeName = fmt.Sprintf("YAML%s", ToCamelCase(responseName))
					// XML:
					case StringInArray(contentTypeName, contentTypesXML):
						typeName = fmt.Sprintf("XML%s", ToCamelCase(responseName))
					default:
						continue
					}

					td := TypeDefinition{
						TypeName:     typeName,
						Schema:       responseSchema,
						ResponseName: responseName,
					}
					if contentType.Schema.Ref != "" {
						refType, err := RefPathToGoType(contentType.Schema.Ref)
						if err != nil {
							return nil, errors.Wrap(err, "error dereferencing response Ref")
						}
						td.Schema.RefType = refType
					}
					tds = append(tds, td)
				}
			}
		}
	}
	return tds, nil
}

// This describes a request body
type RequestBodyDefinition struct {
	// Is this body required, or optional?
	Required bool

	// This is the schema describing this body
	Schema Schema

	// When we generate type names, we need a Tag for it, such as JSON, in
	// which case we will produce "JSONBody".
	NameTag string

	// This is the content type corresponding to the body, eg, application/json
	ContentType string

	// Whether this is the default body type. For an operation named OpFoo, we
	// will not add suffixes like OpFooJSONBody for this one.
	Default bool
}

// Returns the Go type definition for a request body
func (r RequestBodyDefinition) TypeDef() string {
	return r.Schema.TypeDecl()
}

// Returns whether the body is a custom inline type, or pre-defined. This is
// poorly named, but it's here for compatibility reasons post-refactoring
// TODO: clean up the templates code, it can be simpler.
func (r RequestBodyDefinition) CustomType() bool {
	return r.Schema.RefType == ""
}

// When we're generating multiple functions which relate to request bodies,
// this generates the suffix. Such as Operation DoFoo would be suffixed with
// DoFooWithXMLBody.
func (r RequestBodyDefinition) Suffix() string {
	// The default response is never suffixed.
	if r.Default {
		return ""
	}
	return "With" + r.NameTag + "Body"
}

// This function returns the subset of the specified parameters which are of the
// specified type.
func FilterParameterDefinitionByType(params []ParameterDefinition, in string) []ParameterDefinition {
	var out []ParameterDefinition
	for _, p := range params {
		if p.In == in {
			out = append(out, p)
		}
	}
	return out
}

// OperationDefinitions returns all operations for a swagger definition.
func OperationDefinitions(swagger *openapi3.Swagger) ([]OperationDefinition, error) {
	var operations []OperationDefinition

	for _, requestPath := range SortedPathsKeys(swagger.Paths) {
		pathItem := swagger.Paths[requestPath]
		// These are parameters defined for all methods on a given path. They
		// are shared by all methods.
		globalParams, err := DescribeParameters(pathItem.Parameters, nil)
		if err != nil {
			return nil, fmt.Errorf("error describing global parameters for %s: %s",
				requestPath, err)
		}

		// Each path can have a number of operations, POST, GET, OPTIONS, etc.
		pathOps := pathItem.Operations()
		for _, opName := range SortedOperationsKeys(pathOps) {
			op := pathOps[opName]
			// We rely on OperationID to generate function names, it's required
			if op.OperationID == "" {
				op.OperationID, err = generateDefaultOperationID(opName, requestPath)
				if err != nil {
					return nil, fmt.Errorf("error generating default OperationID for %s/%s: %s",
						opName, requestPath, err)
				}
				op.OperationID = op.OperationID
			} else {
				op.OperationID = ToCamelCase(op.OperationID)
			}

			// These are parameters defined for the specific path method that
			// we're iterating over.
			localParams, err := DescribeParameters(op.Parameters, []string{op.OperationID + "Params"})
			if err != nil {
				return nil, fmt.Errorf("error describing global parameters for %s/%s: %s",
					opName, requestPath, err)
			}
			// All the parameters required by a handler are the union of the
			// global parameters and the local parameters.
			allParams := append(globalParams, localParams...)

			// Order the path parameters to match the order as specified in
			// the path, not in the swagger spec, and validate that the parameter
			// names match, as downstream code depends on that.
			pathParams := FilterParameterDefinitionByType(allParams, "path")
			pathParams, err = SortParamsByPath(requestPath, pathParams)
			if err != nil {
				return nil, err
			}

			bodyDefinitions, typeDefinitions, err := GenerateBodyDefinitions(op.OperationID, op.RequestBody)
			if err != nil {
				return nil, errors.Wrap(err, "error generating body definitions")
			}

			opDef := OperationDefinition{
				PathParams:   pathParams,
				HeaderParams: FilterParameterDefinitionByType(allParams, "header"),
				QueryParams:  FilterParameterDefinitionByType(allParams, "query"),
				CookieParams: FilterParameterDefinitionByType(allParams, "cookie"),
				OperationId:  ToCamelCase(op.OperationID),
				// Replace newlines in summary.
				Summary:         op.Summary,
				Method:          opName,
				Path:            requestPath,
				Spec:            op,
				Bodies:          bodyDefinitions,
				TypeDefinitions: typeDefinitions,
			}

			// check for overrides of SecurityDefinitions.
			// See: "Step 2. Applying security:" from the spec:
			// https://swagger.io/docs/specification/authentication/
			if op.Security != nil {
				opDef.SecurityDefinitions = DescribeSecurityDefinition(*op.Security)
			} else {
				// use global securityDefinitions
				// globalSecurityDefinitions contains the top-level securityDefinitions.
				// They are the default securityPermissions which are injected into each
				// path, except for the case where a path explicitly overrides them.
				opDef.SecurityDefinitions = DescribeSecurityDefinition(swagger.Security)

			}

			if op.RequestBody != nil {
				opDef.BodyRequired = op.RequestBody.Value.Required
			}

			// Generate all the type definitions needed for this operation
			opDef.TypeDefinitions = append(opDef.TypeDefinitions, GenerateTypeDefsForOperation(opDef)...)

			operations = append(operations, opDef)
		}
	}
	return operations, nil
}

func generateDefaultOperationID(opName string, requestPath string) (string, error) {
	var operationId string = strings.ToLower(opName)

	if opName == "" {
		return "", fmt.Errorf("operation name cannot be an empty string")
	}

	if requestPath == "" {
		return "", fmt.Errorf("request path cannot be an empty string")
	}

	for _, part := range strings.Split(requestPath, "/") {
		if part != "" {
			operationId = operationId + "-" + part
		}
	}

	return ToCamelCase(operationId), nil
}

// This function turns the Swagger body definitions into a list of our body
// definitions which will be used for code generation.
func GenerateBodyDefinitions(operationID string, bodyOrRef *openapi3.RequestBodyRef) ([]RequestBodyDefinition, []TypeDefinition, error) {
	if bodyOrRef == nil {
		return nil, nil, nil
	}
	body := bodyOrRef.Value

	var bodyDefinitions []RequestBodyDefinition
	var typeDefinitions []TypeDefinition

	for contentType, content := range body.Content {
		var tag string
		var defaultBody bool

		switch contentType {
		case "application/json":
			tag = "JSON"
			defaultBody = true
		default:
			continue
		}

		bodyTypeName := operationID + tag + "Body"
		bodySchema, err := GenerateGoSchema(content.Schema, []string{bodyTypeName})
		if err != nil {
			return nil, nil, errors.Wrap(err, "error generating request body definition")
		}

		// If the body is a pre-defined type
		if bodyOrRef.Ref != "" {
			// Convert the reference path to Go type
			refType, err := RefPathToGoType(bodyOrRef.Ref)
			if err != nil {
				return nil, nil, errors.Wrap(err, fmt.Sprintf("error turning reference (%s) into a Go type", bodyOrRef.Ref))
			}
			bodySchema.RefType = refType
		}

		// If the request has a body, but it's not a user defined
		// type under #/components, we'll define a type for it, so
		// that we have an easy to use type for marshaling.
		if bodySchema.RefType == "" {
			td := TypeDefinition{
				TypeName: bodyTypeName,
				Schema:   bodySchema,
			}
			typeDefinitions = append(typeDefinitions, td)
			// The body schema now is a reference to a type
			bodySchema.RefType = bodyTypeName
		}

		bd := RequestBodyDefinition{
			Required:    body.Required,
			Schema:      bodySchema,
			NameTag:     tag,
			ContentType: contentType,
			Default:     defaultBody,
		}
		bodyDefinitions = append(bodyDefinitions, bd)
	}
	return bodyDefinitions, typeDefinitions, nil
}

func GenerateTypeDefsForOperation(op OperationDefinition) []TypeDefinition {
	var typeDefs []TypeDefinition
	// Start with the params object itself
	if len(op.Params()) != 0 {
		typeDefs = append(typeDefs, GenerateParamsTypes(op)...)
	}

	// Now, go through all the additional types we need to declare.
	for _, param := range op.AllParams() {
		typeDefs = append(typeDefs, param.Schema.GetAdditionalTypeDefs()...)
	}

	for _, body := range op.Bodies {
		typeDefs = append(typeDefs, body.Schema.GetAdditionalTypeDefs()...)
	}
	return typeDefs
}

// This defines the schema for a parameters definition object which encapsulates
// all the query, header and cookie parameters for an operation.
func GenerateParamsTypes(op OperationDefinition) []TypeDefinition {
	var typeDefs []TypeDefinition

	objectParams := op.QueryParams
	objectParams = append(objectParams, op.HeaderParams...)
	objectParams = append(objectParams, op.CookieParams...)

	typeName := op.OperationId + "Params"

	s := Schema{}
	for _, param := range objectParams {
		pSchema := param.Schema
		if pSchema.HasAdditionalProperties {
			propRefName := strings.Join([]string{typeName, param.GoName()}, "_")
			pSchema.RefType = propRefName
			typeDefs = append(typeDefs, TypeDefinition{
				TypeName: propRefName,
				Schema:   param.Schema,
			})
		}
		prop := Property{
			Description:   param.Spec.Description,
			JsonFieldName: param.ParamName,
			Required:      param.Required,
			Schema:        pSchema,
		}
		s.Properties = append(s.Properties, prop)
	}

	s.GoType = GenStructFromSchema(s)

	td := TypeDefinition{
		TypeName: typeName,
		Schema:   s,
	}
	return append(typeDefs, td)
}

// Generates code for all types produced
func GenerateTypesForOperations(t *template.Template, ops []OperationDefinition) (string, error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)

	err := t.ExecuteTemplate(w, "param-types.tmpl", ops)
	if err != nil {
		return "", errors.Wrap(err, "error generating types for params objects")
	}

	err = t.ExecuteTemplate(w, "request-bodies.tmpl", ops)
	if err != nil {
		return "", errors.Wrap(err, "error generating request bodies for operations")
	}

	// Generate boiler plate for all additional types.
	var td []TypeDefinition
	for _, op := range ops {
		td = append(td, op.TypeDefinitions...)
	}

	addProps, err := GenerateAdditionalPropertyBoilerplate(t, td)
	if err != nil {
		return "", errors.Wrap(err, "error generating additional properties boilerplate for operations")
	}

	_, err = w.WriteString("\n")
	if err != nil {
		return "", errors.Wrap(err, "error generating additional properties boilerplate for operations")
	}

	_, err = w.WriteString(addProps)
	if err != nil {
		return "", errors.Wrap(err, "error generating additional properties boilerplate for operations")
	}

	err = w.Flush()
	if err != nil {
		return "", errors.Wrap(err, "error flushing output buffer for server interface")
	}

	return buf.String(), nil
}

// GenerateChiServer This function generates all the go code for the ServerInterface as well as
// all the wrapper functions around our handlers.
func GenerateChiServer(t *template.Template, operations []OperationDefinition) (string, error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)

	err := t.ExecuteTemplate(w, "chi-interface.tmpl", operations)
	if err != nil {
		return "", errors.Wrap(err, "error generating server interface")
	}

	err = t.ExecuteTemplate(w, "chi-middleware.tmpl", operations)
	if err != nil {
		return "", errors.Wrap(err, "error generating server middleware")
	}

	err = t.ExecuteTemplate(w, "chi-handler.tmpl", operations)
	if err != nil {
		return "", errors.Wrap(err, "error generating server http handler")
	}

	err = w.Flush()
	if err != nil {
		return "", errors.Wrap(err, "error flushing output buffer for server")
	}

	return buf.String(), nil
}

// GenerateEchoServer This function generates all the go code for the ServerInterface as well as
// all the wrapper functions around our handlers.
func GenerateEchoServer(t *template.Template, operations []OperationDefinition) (string, error) {
	si, err := GenerateServerInterface(t, operations)
	if err != nil {
		return "", fmt.Errorf("Error generating server types and interface: %s", err)
	}

	wrappers, err := GenerateWrappers(t, operations)
	if err != nil {
		return "", fmt.Errorf("Error generating handler wrappers: %s", err)
	}

	register, err := GenerateRegistration(t, operations)
	if err != nil {
		return "", fmt.Errorf("Error generating handler registration: %s", err)
	}
	return strings.Join([]string{si, wrappers, register}, "\n"), nil
}

// Uses the template engine to generate the server interface
func GenerateServerInterface(t *template.Template, ops []OperationDefinition) (string, error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)

	err := t.ExecuteTemplate(w, "server-interface.tmpl", ops)

	if err != nil {
		return "", fmt.Errorf("error generating server interface: %s", err)
	}
	err = w.Flush()
	if err != nil {
		return "", fmt.Errorf("error flushing output buffer for server interface: %s", err)
	}
	return buf.String(), nil
}

// Uses the template engine to generate all the wrappers which wrap our simple
// interface functions and perform marshallin/unmarshalling from HTTP
// request objects.
func GenerateWrappers(t *template.Template, ops []OperationDefinition) (string, error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)

	err := t.ExecuteTemplate(w, "wrappers.tmpl", ops)

	if err != nil {
		return "", fmt.Errorf("error generating server interface: %s", err)
	}
	err = w.Flush()
	if err != nil {
		return "", fmt.Errorf("error flushing output buffer for server interface: %s", err)
	}
	return buf.String(), nil
}

// Uses the template engine to generate the function which registers our wrappers
// as Echo path handlers.
func GenerateRegistration(t *template.Template, ops []OperationDefinition) (string, error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)

	err := t.ExecuteTemplate(w, "register.tmpl", ops)

	if err != nil {
		return "", fmt.Errorf("error generating route registration: %s", err)
	}
	err = w.Flush()
	if err != nil {
		return "", fmt.Errorf("error flushing output buffer for route registration: %s", err)
	}
	return buf.String(), nil
}

// Uses the template engine to generate the function which registers our wrappers
// as Echo path handlers.
func GenerateClient(t *template.Template, ops []OperationDefinition) (string, error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)

	err := t.ExecuteTemplate(w, "client.tmpl", ops)

	if err != nil {
		return "", fmt.Errorf("error generating client bindings: %s", err)
	}
	err = w.Flush()
	if err != nil {
		return "", fmt.Errorf("error flushing output buffer for client: %s", err)
	}
	return buf.String(), nil
}

// This generates a client which extends the basic client which does response
// unmarshaling.
func GenerateClientWithResponses(t *template.Template, ops []OperationDefinition) (string, error) {
	var buf bytes.Buffer
	w := bufio.NewWriter(&buf)

	err := t.ExecuteTemplate(w, "client-with-responses.tmpl", ops)

	if err != nil {
		return "", fmt.Errorf("error generating client bindings: %s", err)
	}
	err = w.Flush()
	if err != nil {
		return "", fmt.Errorf("error flushing output buffer for client: %s", err)
	}
	return buf.String(), nil
}