// Copyright 2019 CUE 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.

// Package http provides tasks related to the HTTP protocol.
package http

import (
	"io"
	"io/ioutil"
	"net/http"

	"cuelang.org/go/cue"
	"cuelang.org/go/internal/task"
)

func init() {
	task.Register("tool/http.Do", newHTTPCmd)

	// For backwards compatibility.
	task.Register("http", newHTTPCmd)
}

type httpCmd struct{}

func newHTTPCmd(v cue.Value) (task.Runner, error) {
	return &httpCmd{}, nil
}

func lookupString(obj cue.Value, key string) string {
	str, err := obj.Lookup(key).String()
	if err != nil {
		return ""
	}
	return str
}

func (c *httpCmd) Run(ctx *task.Context, v cue.Value) (res interface{}, err error) {
	var header, trailer http.Header
	method := lookupString(v, "method")
	u := lookupString(v, "url")
	var r io.Reader
	if obj := v.Lookup("request"); v.Exists() {
		if v := obj.Lookup("body"); v.Exists() {
			r, err = v.Reader()
			if err != nil {
				return nil, err
			}
		}
		if header, err = parseHeaders(obj, "header"); err != nil {
			return nil, err
		}
		if trailer, err = parseHeaders(obj, "trailer"); err != nil {
			return nil, err
		}
	}
	req, err := http.NewRequest(method, u, r)
	if err != nil {
		return nil, err
	}
	req.Header = header
	req.Trailer = trailer

	// TODO:
	//  - retry logic
	//  - TLS certs
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	b, err := ioutil.ReadAll(resp.Body)
	// parse response body and headers
	return map[string]interface{}{
		"response": map[string]interface{}{
			"body":    string(b),
			"header":  resp.Header,
			"trailer": resp.Trailer,
		},
	}, err
}

func parseHeaders(obj cue.Value, label string) (http.Header, error) {
	m := obj.Lookup(label)
	if !m.Exists() {
		return nil, nil
	}
	iter, err := m.Fields()
	if err != nil {
		return nil, err
	}
	var h http.Header
	for iter.Next() {
		str, err := iter.Value().String()
		if err != nil {
			return nil, err
		}
		h.Add(iter.Label(), str)
	}
	return h, nil
}