// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements.  See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You 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 plugin

import (
	"errors"
	"fmt"
	"net/http"

	hrc "github.com/api7/ext-plugin-proto/go/A6/HTTPReqCall"
	flatbuffers "github.com/google/flatbuffers/go"

	inHTTP "github.com/apache/apisix-go-plugin-runner/internal/http"
	"github.com/apache/apisix-go-plugin-runner/internal/log"
	"github.com/apache/apisix-go-plugin-runner/internal/util"
	pkgHTTP "github.com/apache/apisix-go-plugin-runner/pkg/http"
)

type ParseConfFunc func(in []byte) (conf interface{}, err error)
type FilterFunc func(conf interface{}, w http.ResponseWriter, r pkgHTTP.Request)

type pluginOpts struct {
	ParseConf ParseConfFunc
	Filter    FilterFunc
}

type ErrPluginRegistered struct {
	name string
}

func (err ErrPluginRegistered) Error() string {
	return fmt.Sprintf("plugin %s registered", err.name)
}

var (
	pluginRegistry = map[string]*pluginOpts{}

	ErrMissingName            = errors.New("missing name")
	ErrMissingParseConfMethod = errors.New("missing ParseConf method")
	ErrMissingFilterMethod    = errors.New("missing Filter method")
)

func RegisterPlugin(name string, pc ParseConfFunc, sv FilterFunc) error {
	if name == "" {
		return ErrMissingName
	}
	if pc == nil {
		return ErrMissingParseConfMethod
	}
	if sv == nil {
		return ErrMissingFilterMethod
	}

	opt := &pluginOpts{
		ParseConf: pc,
		Filter:    sv,
	}
	if _, found := pluginRegistry[name]; found {
		return ErrPluginRegistered{name}
	}
	pluginRegistry[name] = opt
	return nil
}

func findPlugin(name string) *pluginOpts {
	if opt, found := pluginRegistry[name]; found {
		return opt
	}
	return nil
}

func filter(conf RuleConf, w *inHTTP.Response, r pkgHTTP.Request) error {
	for _, c := range conf {
		plugin := findPlugin(c.Name)
		if plugin == nil {
			log.Warnf("can't find plugin %s, skip", c.Name)
			continue
		}

		log.Infof("run plugin %s", c.Name)

		plugin.Filter(c.Value, w, r)

		if w.HasChange() {
			// response is generated, no need to continue
			break
		}
	}
	return nil
}

func reportAction(id uint32, req *inHTTP.Request, resp *inHTTP.Response) *flatbuffers.Builder {
	builder := util.GetBuilder()

	if resp != nil && resp.FetchChanges(id, builder) {
		return builder
	}

	if req != nil && req.FetchChanges(id, builder) {
		return builder
	}

	hrc.RespStart(builder)
	hrc.RespAddId(builder, id)
	res := hrc.RespEnd(builder)
	builder.Finish(res)
	return builder
}

func HTTPReqCall(buf []byte) (*flatbuffers.Builder, error) {
	req := inHTTP.CreateRequest(buf)
	defer inHTTP.ReuseRequest(req)

	resp := inHTTP.CreateResponse()
	defer inHTTP.ReuseResponse(resp)

	token := req.ConfToken()
	conf, err := GetRuleConf(token)
	if err != nil {
		return nil, err
	}

	err = filter(conf, resp, req)
	if err != nil {
		return nil, err
	}

	id := req.ID()
	builder := reportAction(id, req, resp)
	return builder, nil
}