/*
 Copyright 2021 The CloudEvents Authors
 SPDX-License-Identifier: Apache-2.0
*/

package http

import (
	"fmt"
	"net"
	nethttp "net/http"
	"net/url"
	"strings"
	"time"
)

// Option is the function signature required to be considered an http.Option.
type Option func(*Protocol) error

// WithTarget sets the outbound recipient of cloudevents when using an HTTP
// request.
func WithTarget(targetUrl string) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http target option can not set nil protocol")
		}
		targetUrl = strings.TrimSpace(targetUrl)
		if targetUrl != "" {
			var err error
			var target *url.URL
			target, err = url.Parse(targetUrl)
			if err != nil {
				return fmt.Errorf("http target option failed to parse target url: %s", err.Error())
			}

			p.Target = target

			if p.RequestTemplate == nil {
				p.RequestTemplate = &nethttp.Request{
					Method: nethttp.MethodPost,
				}
			}
			p.RequestTemplate.URL = target

			return nil
		}
		return fmt.Errorf("http target option was empty string")
	}
}

// WithHeader sets an additional default outbound header for all cloudevents
// when using an HTTP request.
func WithHeader(key, value string) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http header option can not set nil protocol")
		}
		key = strings.TrimSpace(key)
		if key != "" {
			if p.RequestTemplate == nil {
				p.RequestTemplate = &nethttp.Request{
					Method: nethttp.MethodPost,
				}
			}
			if p.RequestTemplate.Header == nil {
				p.RequestTemplate.Header = nethttp.Header{}
			}
			p.RequestTemplate.Header.Add(key, value)
			return nil
		}
		return fmt.Errorf("http header option was empty string")
	}
}

// WithShutdownTimeout sets the shutdown timeout when the http server is being shutdown.
func WithShutdownTimeout(timeout time.Duration) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http shutdown timeout option can not set nil protocol")
		}
		p.ShutdownTimeout = timeout
		return nil
	}
}

func checkListen(p *Protocol, prefix string) error {
	switch {
	case p.listener.Load() != nil:
		return fmt.Errorf("error setting %v: listener already set", prefix)
	}
	return nil
}

// WithPort sets the listening port for StartReceiver.
// Only one of WithListener or WithPort is allowed.
func WithPort(port int) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http port option can not set nil protocol")
		}
		if port < 0 || port > 65535 {
			return fmt.Errorf("http port option was given an invalid port: %d", port)
		}
		if err := checkListen(p, "http port option"); err != nil {
			return err
		}
		p.Port = port
		return nil
	}
}

// WithListener sets the listener for StartReceiver.
// Only one of WithListener or WithPort is allowed.
func WithListener(l net.Listener) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http listener option can not set nil protocol")
		}
		if err := checkListen(p, "http listener"); err != nil {
			return err
		}
		p.listener.Store(l)
		return nil
	}
}

// WithPath sets the path to receive cloudevents on for HTTP transports.
func WithPath(path string) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http path option can not set nil protocol")
		}
		path = strings.TrimSpace(path)
		if len(path) == 0 {
			return fmt.Errorf("http path option was given an invalid path: %q", path)
		}
		p.Path = path
		return nil
	}
}

// WithMethod sets the HTTP verb (GET, POST, PUT, etc.) to use
// when using an HTTP request.
func WithMethod(method string) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http method option can not set nil protocol")
		}
		method = strings.TrimSpace(method)
		if method != "" {
			if p.RequestTemplate == nil {
				p.RequestTemplate = &nethttp.Request{}
			}
			p.RequestTemplate.Method = method
			return nil
		}
		return fmt.Errorf("http method option was empty string")
	}
}

// Middleware is a function that takes an existing http.Handler and wraps it in middleware,
// returning the wrapped http.Handler.
type Middleware func(next nethttp.Handler) nethttp.Handler

// WithMiddleware adds an HTTP middleware to the transport. It may be specified multiple times.
// Middleware is applied to everything before it. For example
// `NewClient(WithMiddleware(foo), WithMiddleware(bar))` would result in `bar(foo(original))`.
func WithMiddleware(middleware Middleware) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http middleware option can not set nil protocol")
		}
		p.middleware = append(p.middleware, middleware)
		return nil
	}
}

// WithRoundTripper sets the HTTP RoundTripper.
func WithRoundTripper(roundTripper nethttp.RoundTripper) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http round tripper option can not set nil protocol")
		}
		p.roundTripper = roundTripper
		return nil
	}
}

// WithRoundTripperDecorator decorates the default HTTP RoundTripper chosen.
func WithRoundTripperDecorator(decorator func(roundTripper nethttp.RoundTripper) nethttp.RoundTripper) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http round tripper option can not set nil protocol")
		}
		if p.roundTripper == nil {
			if p.Client == nil {
				p.roundTripper = nethttp.DefaultTransport
			} else {
				p.roundTripper = p.Client.Transport
			}
		}
		p.roundTripper = decorator(p.roundTripper)
		return nil
	}
}

// WithClient sets the protocol client
func WithClient(client nethttp.Client) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("client option can not set nil protocol")
		}
		p.Client = &client
		return nil
	}
}

// WithGetHandlerFunc sets the http GET handler func
func WithGetHandlerFunc(fn nethttp.HandlerFunc) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http GET handler func can not set nil protocol")
		}
		p.GetHandlerFn = fn
		return nil
	}
}

// WithOptionsHandlerFunc sets the http OPTIONS handler func
func WithOptionsHandlerFunc(fn nethttp.HandlerFunc) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http OPTIONS handler func can not set nil protocol")
		}
		p.OptionsHandlerFn = fn
		return nil
	}
}

// WithDefaultOptionsHandlerFunc sets the options handler to be the built in handler and configures the options.
// methods: the supported methods reported to OPTIONS caller.
// rate: the rate limit reported to OPTIONS caller.
// origins: the prefix of the accepted origins, or "*".
// callback: preform the callback to ACK the OPTIONS request.
func WithDefaultOptionsHandlerFunc(methods []string, rate int, origins []string, callback bool) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http OPTIONS handler func can not set nil protocol")
		}
		p.OptionsHandlerFn = p.OptionsHandler
		p.WebhookConfig = &WebhookConfig{
			AllowedMethods:  methods,
			AllowedRate:     &rate,
			AllowedOrigins:  origins,
			AutoACKCallback: callback,
		}
		return nil
	}
}

// IsRetriable is a custom function that can be used to override the
// default retriable status codes.
type IsRetriable func(statusCode int) bool

// WithIsRetriableFunc sets the function that gets called to determine if an
// error should be retried. If not set, the defaultIsRetriableFunc is used.
func WithIsRetriableFunc(isRetriable IsRetriable) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("isRetriable handler func can not set nil protocol")
		}
		if isRetriable == nil {
			return fmt.Errorf("isRetriable handler can not be nil")
		}
		p.isRetriableFunc = isRetriable
		return nil
	}
}

func WithRateLimiter(rl RateLimiter) Option {
	return func(p *Protocol) error {
		if p == nil {
			return fmt.Errorf("http OPTIONS handler func can not set nil protocol")
		}
		p.limiter = rl
		return nil
	}
}

// WithRequestDataAtContextMiddleware adds to the Context RequestData.
// This enables a user's dispatch handler to inspect HTTP request information by
// retrieving it from the Context.
func WithRequestDataAtContextMiddleware() Option {
	return WithMiddleware(func(next nethttp.Handler) nethttp.Handler {
		return nethttp.HandlerFunc(func(w nethttp.ResponseWriter, r *nethttp.Request) {
			ctx := WithRequestDataAtContext(r.Context(), r)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	})
}