// Copyright 2015 Google Inc. All Rights Reserved.
//
// 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 gcs

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"

	"github.com/jacobsa/gcloud/httputil"
	"golang.org/x/net/context"
	"google.golang.org/api/googleapi"
	storagev1 "google.golang.org/api/storage/v1"
)

// Bucket represents a GCS bucket, pre-bound with a bucket name and necessary
// authorization information.
//
// Each method that may block accepts a context object that is used for
// deadlines and cancellation. Users need not package authorization information
// into the context object (using cloud.WithContext or similar).
//
// All methods are safe for concurrent access.
type Bucket interface {
	Name() string

	// Create a reader for the contents of a particular generation of an object.
	// On a nil error, the caller must arrange for the reader to be closed when
	// it is no longer needed.
	//
	// Non-existent objects cause either this method or the first read from the
	// resulting reader to return an error of type *NotFoundError.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/get
	NewReader(
		ctx context.Context,
		req *ReadObjectRequest) (io.ReadCloser, error)

	// Create or overwrite an object according to the supplied request. The new
	// object is guaranteed to exist immediately for the purposes of reading (and
	// eventually for listing) after this method returns a nil error. It is
	// guaranteed not to exist before req.Contents returns io.EOF.
	//
	// If the request fails due to a precondition not being met, the error will
	// be of type *PreconditionError.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/insert
	//     https://cloud.google.com/storage/docs/json_api/v1/how-tos/upload
	CreateObject(
		ctx context.Context,
		req *CreateObjectRequest) (*Object, error)

	// Copy an object to a new name, preserving all metadata. Any existing
	// generation of the destination name will be overwritten.
	//
	// Returns a record for the new object.
	//
	// If the source object doesn't exist, err will be of type *NotFoundError.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/copy
	CopyObject(
		ctx context.Context,
		req *CopyObjectRequest) (*Object, error)

	// Compose zero or more source objects into a single destination object by
	// concatenating. Any existing generation of the destination name will be
	// overwritten.
	//
	// Returns a record for the new object.
	//
	// If any of the sources don't exist, err will be of type *NotFoundError. If
	// the request fails due to a precondition not being met, the error will be
	// of type *PreconditionError.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/compose
	ComposeObjects(
		ctx context.Context,
		req *ComposeObjectsRequest) (*Object, error)

	// Return current information about the object with the given name.
	//
	// If the object doesn't exist, err will be of type *NotFoundError.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/get
	StatObject(
		ctx context.Context,
		req *StatObjectRequest) (*Object, error)

	// List the objects in the bucket that meet the criteria defined by the
	// request, returning a result object that contains the results and
	// potentially a cursor for retrieving the next portion of the larger set of
	// results.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/list
	ListObjects(
		ctx context.Context,
		req *ListObjectsRequest) (*Listing, error)

	// Update the object specified by newAttrs.Name, patching using the non-zero
	// fields of newAttrs.
	//
	// If the object doesn't exist, err will be of type *NotFoundError.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/patch
	UpdateObject(
		ctx context.Context,
		req *UpdateObjectRequest) (*Object, error)

	// Delete an object. Non-existence of the object is not treated as an error.
	//
	// Official documentation:
	//     https://cloud.google.com/storage/docs/json_api/v1/objects/delete
	DeleteObject(
		ctx context.Context,
		req *DeleteObjectRequest) error
}

type bucket struct {
	client    *http.Client
	userAgent string
	name      string
}

func (b *bucket) Name() string {
	return b.name
}

func (b *bucket) ListObjects(
	ctx context.Context,
	req *ListObjectsRequest) (listing *Listing, err error) {
	// Construct an appropriate URL (cf. http://goo.gl/aVSAhT).
	opaque := fmt.Sprintf(
		"//www.googleapis.com/storage/v1/b/%s/o",
		httputil.EncodePathSegment(b.Name()))

	query := make(url.Values)
	query.Set("projection", "full")

	if req.Prefix != "" {
		query.Set("prefix", req.Prefix)
	}

	if req.Delimiter != "" {
		query.Set("delimiter", req.Delimiter)
	}

	if req.ContinuationToken != "" {
		query.Set("pageToken", req.ContinuationToken)
	}

	if req.MaxResults != 0 {
		query.Set("maxResults", fmt.Sprintf("%v", req.MaxResults))
	}

	url := &url.URL{
		Scheme:   "https",
		Host:     "www.googleapis.com",
		Opaque:   opaque,
		RawQuery: query.Encode(),
	}

	// Create an HTTP request.
	httpReq, err := httputil.NewRequest("GET", url, nil, b.userAgent)
	if err != nil {
		err = fmt.Errorf("httputil.NewRequest: %v", err)
		return
	}

	// Call the server.
	httpRes, err := httputil.Do(ctx, b.client, httpReq)
	if err != nil {
		return
	}

	defer googleapi.CloseBody(httpRes)

	// Check for HTTP-level errors.
	if err = googleapi.CheckResponse(httpRes); err != nil {
		return
	}

	// Parse the response.
	var rawListing *storagev1.Objects
	if err = json.NewDecoder(httpRes.Body).Decode(&rawListing); err != nil {
		return
	}

	// Convert the response.
	if listing, err = toListing(rawListing); err != nil {
		return
	}

	return
}

func (b *bucket) StatObject(
	ctx context.Context,
	req *StatObjectRequest) (o *Object, err error) {
	// Construct an appropriate URL (cf. http://goo.gl/MoITmB).
	opaque := fmt.Sprintf(
		"//www.googleapis.com/storage/v1/b/%s/o/%s",
		httputil.EncodePathSegment(b.Name()),
		httputil.EncodePathSegment(req.Name))

	query := make(url.Values)
	query.Set("projection", "full")

	url := &url.URL{
		Scheme:   "https",
		Host:     "www.googleapis.com",
		Opaque:   opaque,
		RawQuery: query.Encode(),
	}

	// Create an HTTP request.
	httpReq, err := httputil.NewRequest("GET", url, nil, b.userAgent)
	if err != nil {
		err = fmt.Errorf("httputil.NewRequest: %v", err)
		return
	}

	// Execute the HTTP request.
	httpRes, err := httputil.Do(ctx, b.client, httpReq)
	if err != nil {
		return
	}

	defer googleapi.CloseBody(httpRes)

	// Check for HTTP-level errors.
	if err = googleapi.CheckResponse(httpRes); err != nil {
		// Special case: handle not found errors.
		if typed, ok := err.(*googleapi.Error); ok {
			if typed.Code == http.StatusNotFound {
				err = &NotFoundError{Err: typed}
			}
		}

		return
	}

	// Parse the response.
	var rawObject *storagev1.Object
	if err = json.NewDecoder(httpRes.Body).Decode(&rawObject); err != nil {
		return
	}

	// Convert the response.
	if o, err = toObject(rawObject); err != nil {
		err = fmt.Errorf("toObject: %v", err)
		return
	}

	return
}

func (b *bucket) DeleteObject(
	ctx context.Context,
	req *DeleteObjectRequest) (err error) {
	// Construct an appropriate URL (cf. http://goo.gl/TRQJjZ).
	opaque := fmt.Sprintf(
		"//www.googleapis.com/storage/v1/b/%s/o/%s",
		httputil.EncodePathSegment(b.Name()),
		httputil.EncodePathSegment(req.Name))

	query := make(url.Values)
	if req.Generation != 0 {
		query.Set("generation", fmt.Sprintf("%d", req.Generation))
	}

	url := &url.URL{
		Scheme:   "https",
		Host:     "www.googleapis.com",
		Opaque:   opaque,
		RawQuery: query.Encode(),
	}

	// Create an HTTP request.
	httpReq, err := httputil.NewRequest("DELETE", url, nil, b.userAgent)
	if err != nil {
		err = fmt.Errorf("httputil.NewRequest: %v", err)
		return
	}

	// Execute the HTTP request.
	httpRes, err := httputil.Do(ctx, b.client, httpReq)
	if err != nil {
		return
	}

	defer googleapi.CloseBody(httpRes)

	// Check for HTTP-level errors.
	err = googleapi.CheckResponse(httpRes)

	// Special case: we want deletes to be idempotent.
	if typed, ok := err.(*googleapi.Error); ok {
		if typed.Code == http.StatusNotFound {
			err = nil
		}
	}

	// Propagate other errors.
	if err != nil {
		return
	}

	return
}

func newBucket(
	client *http.Client,
	userAgent string,
	name string) Bucket {
	return &bucket{
		client:    client,
		userAgent: userAgent,
		name:      name,
	}
}