//
// goamz - Go packages to interact with the Amazon Web Services.
//
//   https://wiki.ubuntu.com/goamz
//
// Copyright (c) 2011 Memeo Inc.
//
// Written by Prudhvi Krishna Surapaneni <me@prudhvi.net>

// This package is in an experimental state, and does not currently
// follow conventions and style of the rest of goamz or common
// Go conventions. It must be polished before it's considered a
// first-class package in goamz.
package sns

// BUG(niemeyer): Package needs documentation.

import (
	"encoding/xml"
	"net/http"
	"net/url"
	"time"

	"github.com/goamz/goamz/aws"
)

// The SNS type encapsulates operation with an SNS region.
type SNS struct {
	aws.Auth
	aws.Region
	private byte // Reserve the right of using private data.
}

type AttributeEntry struct {
	Key   string `xml:"key"`
	Value string `xml:"value"`
}

type ResponseMetadata struct {
	RequestId string  `xml:"ResponseMetadata>RequestId"`
	BoxUsage  float64 `xml:"ResponseMetadata>BoxUsage"`
}

func New(auth aws.Auth, region aws.Region) *SNS {
	return &SNS{auth, region, 0}
}

func makeParams(action string) map[string]string {
	params := make(map[string]string)
	params["Action"] = action
	return params
}

type Error struct {
	StatusCode int
	Code       string
	Message    string
	RequestId  string
}

func (err *Error) Error() string {
	return err.Message
}

type xmlErrors struct {
	RequestId string
	Errors    []Error `xml:"Errors>Error"`
}

func (sns *SNS) query(params map[string]string, resp interface{}) error {
	params["Timestamp"] = time.Now().UTC().Format(time.RFC3339)
	u, err := url.Parse(sns.Region.SNSEndpoint)
	if err != nil {
		return err
	}

	sign(sns.Auth, "GET", "/", params, u.Host)
	u.RawQuery = multimap(params).Encode()
	r, err := http.Get(u.String())
	if err != nil {
		return err
	}
	defer r.Body.Close()

	if r.StatusCode != 200 {
		return buildError(r)
	}
	err = xml.NewDecoder(r.Body).Decode(resp)
	return err
}

func buildError(r *http.Response) error {
	errors := xmlErrors{}
	xml.NewDecoder(r.Body).Decode(&errors)
	var err Error
	if len(errors.Errors) > 0 {
		err = errors.Errors[0]
	}
	err.RequestId = errors.RequestId
	err.StatusCode = r.StatusCode
	if err.Message == "" {
		err.Message = r.Status
	}
	return &err
}

func multimap(p map[string]string) url.Values {
	q := make(url.Values, len(p))
	for k, v := range p {
		q[k] = []string{v}
	}
	return q
}