// 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 bigquery

import (
	"time"

	"cloud.google.com/go/internal/optional"

	"golang.org/x/net/context"
	"google.golang.org/api/iterator"
)

// Dataset is a reference to a BigQuery dataset.
type Dataset struct {
	ProjectID string
	DatasetID string
	c         *Client
}

// DatasetMetadata contains information about a BigQuery dataset.
type DatasetMetadata struct {
	// These fields can be set when creating a dataset.
	Name                   string            // The user-friendly name for this dataset.
	Description            string            // The user-friendly description of this dataset.
	Location               string            // The geo location of the dataset.
	DefaultTableExpiration time.Duration     // The default expiration time for new tables.
	Labels                 map[string]string // User-provided labels.

	// These fields are read-only.
	CreationTime     time.Time
	LastModifiedTime time.Time // When the dataset or any of its tables were modified.
	FullID           string    // The full dataset ID in the form projectID:datasetID.

	// ETag is the ETag obtained when reading metadata. Pass it to Dataset.Update to
	// ensure that the metadata hasn't changed since it was read.
	ETag string
	// TODO(jba): access rules
}

// DatasetMetadataToUpdate is used when updating a dataset's metadata.
// Only non-nil fields will be updated.
type DatasetMetadataToUpdate struct {
	Description optional.String // The user-friendly description of this table.
	Name        optional.String // The user-friendly name for this dataset.
	// DefaultTableExpiration is the the default expiration time for new tables.
	// If set to time.Duration(0), new tables never expire.
	DefaultTableExpiration optional.Duration

	setLabels    map[string]string
	deleteLabels map[string]bool
}

// SetLabel causes a label to be added or modified when dm is used
// in a call to Dataset.Update.
func (dm *DatasetMetadataToUpdate) SetLabel(name, value string) {
	if dm.setLabels == nil {
		dm.setLabels = map[string]string{}
	}
	dm.setLabels[name] = value
}

// DeleteLabel causes a label to be deleted when dm is used in a
// call to Dataset.Update.
func (dm *DatasetMetadataToUpdate) DeleteLabel(name string) {
	if dm.deleteLabels == nil {
		dm.deleteLabels = map[string]bool{}
	}
	dm.deleteLabels[name] = true
}

// Dataset creates a handle to a BigQuery dataset in the client's project.
func (c *Client) Dataset(id string) *Dataset {
	return c.DatasetInProject(c.projectID, id)
}

// DatasetInProject creates a handle to a BigQuery dataset in the specified project.
func (c *Client) DatasetInProject(projectID, datasetID string) *Dataset {
	return &Dataset{
		ProjectID: projectID,
		DatasetID: datasetID,
		c:         c,
	}
}

// Create creates a dataset in the BigQuery service. An error will be returned if the
// dataset already exists. Pass in a DatasetMetadata value to configure the dataset.
func (d *Dataset) Create(ctx context.Context, md *DatasetMetadata) error {
	return d.c.service.insertDataset(ctx, d.DatasetID, d.ProjectID, md)
}

// Delete deletes the dataset.
func (d *Dataset) Delete(ctx context.Context) error {
	return d.c.service.deleteDataset(ctx, d.DatasetID, d.ProjectID)
}

// Metadata fetches the metadata for the dataset.
func (d *Dataset) Metadata(ctx context.Context) (*DatasetMetadata, error) {
	return d.c.service.getDatasetMetadata(ctx, d.ProjectID, d.DatasetID)
}

// Update modifies specific Dataset metadata fields.
// To perform a read-modify-write that protects against intervening reads,
// set the etag argument to the DatasetMetadata.ETag field from the read.
// Pass the empty string for etag for a "blind write" that will always succeed.
func (d *Dataset) Update(ctx context.Context, dm DatasetMetadataToUpdate, etag string) (*DatasetMetadata, error) {
	return d.c.service.patchDataset(ctx, d.ProjectID, d.DatasetID, &dm, etag)
}

// Table creates a handle to a BigQuery table in the dataset.
// To determine if a table exists, call Table.Metadata.
// If the table does not already exist, use Table.Create to create it.
func (d *Dataset) Table(tableID string) *Table {
	return &Table{ProjectID: d.ProjectID, DatasetID: d.DatasetID, TableID: tableID, c: d.c}
}

// Tables returns an iterator over the tables in the Dataset.
func (d *Dataset) Tables(ctx context.Context) *TableIterator {
	it := &TableIterator{
		ctx:     ctx,
		dataset: d,
	}
	it.pageInfo, it.nextFunc = iterator.NewPageInfo(
		it.fetch,
		func() int { return len(it.tables) },
		func() interface{} { b := it.tables; it.tables = nil; return b })
	return it
}

// A TableIterator is an iterator over Tables.
type TableIterator struct {
	ctx      context.Context
	dataset  *Dataset
	tables   []*Table
	pageInfo *iterator.PageInfo
	nextFunc func() error
}

// Next returns the next result. Its second return value is Done if there are
// no more results. Once Next returns Done, all subsequent calls will return
// Done.
func (it *TableIterator) Next() (*Table, error) {
	if err := it.nextFunc(); err != nil {
		return nil, err
	}
	t := it.tables[0]
	it.tables = it.tables[1:]
	return t, nil
}

// PageInfo supports pagination. See the google.golang.org/api/iterator package for details.
func (it *TableIterator) PageInfo() *iterator.PageInfo { return it.pageInfo }

func (it *TableIterator) fetch(pageSize int, pageToken string) (string, error) {
	tables, tok, err := it.dataset.c.service.listTables(it.ctx, it.dataset.ProjectID, it.dataset.DatasetID, pageSize, pageToken)
	if err != nil {
		return "", err
	}
	for _, t := range tables {
		t.c = it.dataset.c
		it.tables = append(it.tables, t)
	}
	return tok, nil
}

// Datasets returns an iterator over the datasets in a project.
// The Client's project is used by default, but that can be
// changed by setting ProjectID on the returned iterator before calling Next.
func (c *Client) Datasets(ctx context.Context) *DatasetIterator {
	return c.DatasetsInProject(ctx, c.projectID)
}

// DatasetsInProject returns an iterator over the datasets in the provided project.
//
// Deprecated: call Client.Datasets, then set ProjectID on the returned iterator.
func (c *Client) DatasetsInProject(ctx context.Context, projectID string) *DatasetIterator {
	it := &DatasetIterator{
		ctx:       ctx,
		c:         c,
		ProjectID: projectID,
	}
	it.pageInfo, it.nextFunc = iterator.NewPageInfo(
		it.fetch,
		func() int { return len(it.items) },
		func() interface{} { b := it.items; it.items = nil; return b })
	return it
}

// DatasetIterator iterates over the datasets in a project.
type DatasetIterator struct {
	// ListHidden causes hidden datasets to be listed when set to true.
	// Set before the first call to Next.
	ListHidden bool

	// Filter restricts the datasets returned by label. The filter syntax is described in
	// https://cloud.google.com/bigquery/docs/labeling-datasets#filtering_datasets_using_labels
	// Set before the first call to Next.
	Filter string

	// The project ID of the listed datasets.
	// Set before the first call to Next.
	ProjectID string

	ctx      context.Context
	c        *Client
	pageInfo *iterator.PageInfo
	nextFunc func() error
	items    []*Dataset
}

// PageInfo supports pagination. See the google.golang.org/api/iterator package for details.
func (it *DatasetIterator) PageInfo() *iterator.PageInfo { return it.pageInfo }

func (it *DatasetIterator) Next() (*Dataset, error) {
	if err := it.nextFunc(); err != nil {
		return nil, err
	}
	item := it.items[0]
	it.items = it.items[1:]
	return item, nil
}

func (it *DatasetIterator) fetch(pageSize int, pageToken string) (string, error) {
	datasets, nextPageToken, err := it.c.service.listDatasets(it.ctx, it.ProjectID,
		pageSize, pageToken, it.ListHidden, it.Filter)
	if err != nil {
		return "", err
	}
	for _, d := range datasets {
		d.c = it.c
		it.items = append(it.items, d)
	}
	return nextPageToken, nil
}