package pkg

/*
Copyright 2024 Jonas Kaninda

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.
*/
import (
	"context"
	"fmt"
	"github.com/jkaninda/goma-gateway/internal/logger"
	"github.com/jkaninda/goma-gateway/util"
	"github.com/spf13/cobra"
	"gopkg.in/yaml.v3"
	"os"
)

var cfg *Gateway

type Config struct {
	file string
}
type BasicRuleMiddleware struct {
	Username string `yaml:"username"`
	Password string `yaml:"password"`
}

type Cors struct {
	// Cors Allowed origins,
	//e.g:
	//
	// - http://localhost:80
	//
	// - https://example.com
	Origins []string `yaml:"origins"`
	//
	//e.g:
	//
	//Access-Control-Allow-Origin: '*'
	//
	//    Access-Control-Allow-Methods: 'GET, POST, PUT, DELETE, OPTIONS'
	//
	//    Access-Control-Allow-Cors: 'Content-Type, Authorization'
	Headers map[string]string `yaml:"headers"`
}

// JWTRuleMiddleware authentication using HTTP GET method
//
// JWTRuleMiddleware contains the authentication details
type JWTRuleMiddleware struct {
	// URL contains the authentication URL, it supports HTTP GET method only.
	URL string `yaml:"url"`
	// RequiredHeaders , contains required before sending request to the backend.
	RequiredHeaders []string `yaml:"requiredHeaders"`
	// Headers Add header to the backend from Authentication request's header, depending on your requirements.
	// Key is Http's response header Key, and value  is the backend Request's header Key.
	// In case you want to get headers from Authentication service and inject them to backend request's headers.
	Headers map[string]string `yaml:"headers"`
	// Params same as Headers, contains the request params.
	//
	// Gets authentication headers from authentication request and inject them as request params to the backend.
	//
	// Key is Http's response header Key, and value  is the backend Request's request param Key.
	//
	// In case you want to get headers from Authentication service and inject them to next request's params.
	//
	//e.g: Header X-Auth-UserId to query userId
	Params map[string]string `yaml:"params"`
}
type RateLimiter struct {
	// ipBased, tokenBased
	Type string  `yaml:"type"`
	Rate float64 `yaml:"rate"`
	Rule int     `yaml:"rule"`
}

type AccessRuleMiddleware struct {
	ResponseCode int `yaml:"responseCode"` // HTTP Response code
}

// Middleware defined the route middleware
type Middleware struct {
	//Path contains the name of middleware and must be unique
	Name string `yaml:"name"`
	// Type contains authentication types
	//
	// basic, jwt, auth0, rateLimit, access
	Type  string   `yaml:"type"`  // Middleware type [basic, jwt, auth0, rateLimit, access]
	Paths []string `yaml:"paths"` // Protected paths
	// Rule contains rule type of
	Rule interface{} `yaml:"rule"` // Middleware rule
}
type MiddlewareName struct {
	name string `yaml:"name"`
}

// Route defines gateway route
type Route struct {
	// Name defines route name
	Name string `yaml:"name"`
	//Host Domain/host based request routing
	Host string `yaml:"host"`
	// Path defines route path
	Path string `yaml:"path"`
	// Rewrite rewrites route path to desired path
	//
	// E.g. /cart to / => It will rewrite /cart path to /
	Rewrite string `yaml:"rewrite"`
	// Destination Defines backend URL
	Destination string `yaml:"destination"`
	// Cors contains the route cors headers
	Cors Cors `yaml:"cors"`
	// DisableHeaderXForward Disable X-forwarded header.
	//
	// [X-Forwarded-Host, X-Forwarded-For, Host, Scheme ]
	//
	// It will not match the backend route
	DisableHeaderXForward bool `yaml:"disableHeaderXForward"`
	// HealthCheck Defines the backend is health check PATH
	HealthCheck string `yaml:"healthCheck"`
	// InterceptErrors intercepts backend errors based on the status codes
	//
	// Eg: [ 403, 405, 500 ]
	InterceptErrors []int `yaml:"interceptErrors"`
	// Middlewares Defines route middleware from Middleware names
	Middlewares []string `yaml:"middlewares"`
}

// Gateway contains Goma Proxy Gateway's configs
type Gateway struct {
	// ListenAddr Defines the server listenAddr
	//
	//e.g: localhost:8080
	ListenAddr string `yaml:"listenAddr" env:"GOMA_LISTEN_ADDR, overwrite"`
	// WriteTimeout defines proxy write timeout
	WriteTimeout int `yaml:"writeTimeout" env:"GOMA_WRITE_TIMEOUT, overwrite"`
	// ReadTimeout defines proxy read timeout
	ReadTimeout int `yaml:"readTimeout" env:"GOMA_READ_TIMEOUT, overwrite"`
	// IdleTimeout defines proxy idle timeout
	IdleTimeout int `yaml:"idleTimeout" env:"GOMA_IDLE_TIMEOUT, overwrite"`
	// RateLimiter Defines number of request peer minute
	RateLimiter int    `yaml:"rateLimiter" env:"GOMA_RATE_LIMITER, overwrite"`
	AccessLog   string `yaml:"accessLog" env:"GOMA_ACCESS_LOG, overwrite"`
	ErrorLog    string `yaml:"errorLog" env:"GOMA_ERROR_LOG=, overwrite"`
	// DisableRouteHealthCheckError allows enabling and disabling backend healthcheck errors
	DisableRouteHealthCheckError bool `yaml:"disableRouteHealthCheckError"`
	//Disable allows enabling and disabling displaying routes on start
	DisableDisplayRouteOnStart bool `yaml:"disableDisplayRouteOnStart"`
	// DisableKeepAlive allows enabling and disabling KeepALive server
	DisableKeepAlive bool `yaml:"disableKeepAlive"`
	// InterceptErrors holds the status codes to intercept the error from backend
	InterceptErrors []int `yaml:"interceptErrors"`
	// Cors holds proxy global cors
	Cors Cors `yaml:"cors"`
	// Routes holds proxy routes
	Routes []Route `yaml:"routes"`
}
type GatewayConfig struct {
	// GatewayConfig holds Gateway config
	GatewayConfig Gateway `yaml:"gateway"`
	// Middlewares holds proxy middlewares
	Middlewares []Middleware `yaml:"middlewares"`
}

// ErrorResponse represents the structure of the JSON error response
type ErrorResponse struct {
	Success bool   `json:"success"`
	Code    int    `json:"code"`
	Message string `json:"message"`
}
type GatewayServer struct {
	ctx         context.Context
	gateway     Gateway
	middlewares []Middleware
}

// Config reads config file and returns Gateway
func (GatewayServer) Config(configFile string) (*GatewayServer, error) {
	if util.FileExists(configFile) {
		buf, err := os.ReadFile(configFile)
		if err != nil {
			return nil, err
		}
		util.SetEnv("GOMA_CONFIG_FILE", configFile)
		c := &GatewayConfig{}
		err = yaml.Unmarshal(buf, c)
		if err != nil {
			return nil, fmt.Errorf("error parsing yaml %q: %w", configFile, err)
		}
		return &GatewayServer{
			ctx:         nil,
			gateway:     c.GatewayConfig,
			middlewares: c.Middlewares,
		}, nil
	}
	logger.Error("Configuration file not found: %v", configFile)
	logger.Info("Generating new configuration file...")
	initConfig(ConfigFile)
	logger.Info("Server configuration file is available at %s", ConfigFile)
	util.SetEnv("GOMA_CONFIG_FILE", ConfigFile)
	buf, err := os.ReadFile(ConfigFile)
	if err != nil {
		return nil, err
	}
	c := &GatewayConfig{}
	err = yaml.Unmarshal(buf, c)
	if err != nil {
		return nil, fmt.Errorf("in file %q: %w", ConfigFile, err)
	}
	logger.Info("Generating new configuration file...done")
	logger.Info("Starting server with default configuration")
	return &GatewayServer{
		ctx:         nil,
		gateway:     c.GatewayConfig,
		middlewares: c.Middlewares,
	}, nil
}
func GetConfigPaths() string {
	return util.GetStringEnv("GOMAY_CONFIG_FILE", ConfigFile)
}
func InitConfig(cmd *cobra.Command) {
	configFile, _ := cmd.Flags().GetString("output")
	if configFile == "" {
		configFile = GetConfigPaths()
	}
	initConfig(configFile)
	return

}
func initConfig(configFile string) {
	if configFile == "" {
		configFile = GetConfigPaths()
	}
	conf := &GatewayConfig{
		GatewayConfig: Gateway{
			ListenAddr:                   "0.0.0.0:80",
			WriteTimeout:                 15,
			ReadTimeout:                  15,
			IdleTimeout:                  60,
			AccessLog:                    "/dev/Stdout",
			ErrorLog:                     "/dev/stderr",
			DisableRouteHealthCheckError: false,
			DisableDisplayRouteOnStart:   false,
			RateLimiter:                  0,
			InterceptErrors:              []int{405, 500},
			Cors: Cors{
				Origins: []string{"http://localhost:8080", "https://example.com"},
				Headers: map[string]string{
					"Access-Control-Allow-Headers":     "Origin, Authorization, Accept, Content-Type, Access-Control-Allow-Headers, X-Client-Id, X-Session-Id",
					"Access-Control-Allow-Credentials": "true",
					"Access-Control-Max-Age":           "1728000",
				},
			},
			Routes: []Route{
				{
					Name:        "Public",
					Path:        "/public",
					Destination: "https://example.com",
					Rewrite:     "/",
					HealthCheck: "",
					Middlewares: []string{"api-forbidden-paths"},
				},
				{
					Name:        "Basic auth",
					Path:        "/protected",
					Destination: "https://example.com",
					Rewrite:     "/",
					HealthCheck: "",
					Cors: Cors{
						Origins: []string{"http://localhost:3000", "https://dev.example.com"},
						Headers: map[string]string{
							"Access-Control-Allow-Headers":     "Origin, Authorization",
							"Access-Control-Allow-Credentials": "true",
							"Access-Control-Max-Age":           "1728000",
						},
					},
					Middlewares: []string{"basic-auth", "api-forbidden-paths"},
				},
				{
					Name:        "Hostname example",
					Path:        "/",
					Destination: "https://example.com",
					Rewrite:     "/",
					HealthCheck: "",
				},
			},
		},
		Middlewares: []Middleware{
			{
				Name: "basic-auth",
				Type: BasicAuth,
				Paths: []string{
					"/*",
				},
				Rule: BasicRuleMiddleware{
					Username: "admin",
					Password: "admin",
				},
			}, {
				Name: "jwt",
				Type: JWTAuth,
				Paths: []string{
					"/protected-access",
					"/example-of-jwt",
				},
				Rule: JWTRuleMiddleware{
					URL: "https://www.googleapis.com/auth/userinfo.email",
					RequiredHeaders: []string{
						"Authorization",
					},
					Headers: map[string]string{},
					Params:  map[string]string{},
				},
			},
			{
				Name: "api-forbidden-paths",
				Type: AccessMiddleware,
				Paths: []string{
					"/swagger-ui/*",
					"/v2/swagger-ui/*",
					"/api-docs/*",
					"/internal/*",
					"/actuator/*",
				},
			},
		},
	}
	yamlData, err := yaml.Marshal(&conf)
	if err != nil {
		logger.Fatal("Error serializing configuration %v", err.Error())
	}
	err = os.WriteFile(configFile, yamlData, 0644)
	if err != nil {
		logger.Fatal("Unable to write config file %s", err)
	}
	logger.Info("Configuration file has been initialized successfully")
}
func Get() *Gateway {
	if cfg == nil {
		c := &Gateway{}
		c.Setup(GetConfigPaths())
		cfg = c
	}
	return cfg
}
func (Gateway) Setup(conf string) *Gateway {
	if util.FileExists(conf) {
		buf, err := os.ReadFile(conf)
		if err != nil {
			return &Gateway{}
		}
		util.SetEnv("GOMA_CONFIG_FILE", conf)
		c := &GatewayConfig{}
		err = yaml.Unmarshal(buf, c)
		if err != nil {
			logger.Fatal("Error loading configuration %v", err.Error())
		}
		return &c.GatewayConfig
	}
	return &Gateway{}

}

// getJWTMiddleware returns JWTRuleMiddleware,error
func getJWTMiddleware(input interface{}) (JWTRuleMiddleware, error) {
	jWTRuler := new(JWTRuleMiddleware)
	var bytes []byte
	bytes, err := yaml.Marshal(input)
	if err != nil {
		return JWTRuleMiddleware{}, fmt.Errorf("error parsing yaml: %v", err)
	}
	err = yaml.Unmarshal(bytes, jWTRuler)
	if err != nil {
		return JWTRuleMiddleware{}, fmt.Errorf("error parsing yaml: %v", err)
	}
	if jWTRuler.URL == "" {
		return JWTRuleMiddleware{}, fmt.Errorf("error parsing yaml: empty url in jwt auth middleware")

	}
	return *jWTRuler, nil
}

// getBasicAuthMiddleware returns BasicRuleMiddleware,error
func getBasicAuthMiddleware(input interface{}) (BasicRuleMiddleware, error) {
	basicAuth := new(BasicRuleMiddleware)
	var bytes []byte
	bytes, err := yaml.Marshal(input)
	if err != nil {
		return BasicRuleMiddleware{}, fmt.Errorf("error parsing yaml: %v", err)
	}
	err = yaml.Unmarshal(bytes, basicAuth)
	if err != nil {
		return BasicRuleMiddleware{}, fmt.Errorf("error parsing yaml: %v", err)
	}
	if basicAuth.Username == "" || basicAuth.Password == "" {
		return BasicRuleMiddleware{}, fmt.Errorf("error parsing yaml: empty username/password in %s middleware", basicAuth)

	}
	return *basicAuth, nil
}