// 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 memorydb

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"regexp"
	"strings"

	"github.com/go-kivik/kivik/v4"
	"github.com/go-kivik/kivik/v4/driver"
)

var notYetImplemented = statusError{status: http.StatusNotImplemented, error: errors.New("kivik: not yet implemented in memory driver")}

// database is an in-memory database representation.
type db struct {
	*client
	dbName string
	db     *database
}

func (d *db) Query(context.Context, string, string, driver.Options) (driver.Rows, error) {
	// FIXME: Unimplemented
	return nil, notYetImplemented
}

func (d *db) Get(ctx context.Context, docID string, options driver.Options) (*driver.Document, error) {
	if exists, _ := d.client.DBExists(ctx, d.dbName, nil); !exists {
		return nil, statusError{status: http.StatusPreconditionFailed, error: errors.New("database does not exist")}
	}
	if !d.db.docExists(docID) {
		return nil, statusError{status: http.StatusNotFound, error: errors.New("missing")}
	}
	opts := map[string]interface{}{}
	options.Apply(opts)
	if rev, ok := opts["rev"].(string); ok {
		if doc, found := d.db.getRevision(docID, rev); found {
			return &driver.Document{
				Rev:  rev,
				Body: io.NopCloser(bytes.NewReader(doc.data)),
			}, nil
		}
		return nil, statusError{status: http.StatusNotFound, error: errors.New("missing")}
	}
	last, _ := d.db.latestRevision(docID)
	if last.Deleted {
		return nil, statusError{status: http.StatusNotFound, error: errors.New("missing")}
	}
	return &driver.Document{
		Rev:  fmt.Sprintf("%d-%s", last.ID, last.Rev),
		Body: io.NopCloser(bytes.NewReader(last.data)),
	}, nil
}

func (d *db) Put(ctx context.Context, docID string, doc interface{}, _ driver.Options) (rev string, err error) {
	if exists, _ := d.client.DBExists(ctx, d.dbName, nil); !exists {
		return "", statusError{status: http.StatusPreconditionFailed, error: errors.New("database does not exist")}
	}
	isLocal := strings.HasPrefix(docID, "_local/")
	if !isLocal && docID[0] == '_' && !strings.HasPrefix(docID, "_design/") {
		return "", statusError{status: http.StatusBadRequest, error: errors.New("only reserved document ids may start with underscore")}
	}
	couchDoc, err := toCouchDoc(doc)
	if err != nil {
		return "", err
	}
	couchDoc["_id"] = docID
	// TODO: Add support for storing attachments.
	delete(couchDoc, "_attachments")

	if last, ok := d.db.latestRevision(docID); ok {
		if !last.Deleted && !isLocal && couchDoc.Rev() != fmt.Sprintf("%d-%s", last.ID, last.Rev) {
			return "", statusError{status: http.StatusConflict, error: errors.New("document update conflict")}
		}
		return d.db.addRevision(couchDoc), nil
	}

	if couchDoc.Rev() != "" {
		// Rev should not be set for a new document
		return "", statusError{status: http.StatusConflict, error: errors.New("document update conflict")}
	}
	return d.db.addRevision(couchDoc), nil
}

var revRE = regexp.MustCompile("^[0-9]+-[a-f0-9]{32}$")

func validRev(rev string) bool {
	return revRE.MatchString(rev)
}

func (d *db) Delete(ctx context.Context, docID string, options driver.Options) (newRev string, err error) {
	if exists, _ := d.client.DBExists(ctx, d.dbName, kivik.Params(nil)); !exists {
		return "", statusError{status: http.StatusPreconditionFailed, error: errors.New("database does not exist")}
	}
	opts := map[string]interface{}{}
	options.Apply(opts)
	rev, _ := opts["rev"].(string)
	if !strings.HasPrefix(docID, "_local/") && !validRev(rev) {
		return "", statusError{status: http.StatusBadRequest, error: errors.New("invalid rev format")}
	}
	if !d.db.docExists(docID) {
		return "", statusError{status: http.StatusNotFound, error: errors.New("missing")}
	}
	return d.Put(ctx, docID, map[string]interface{}{
		"_id":      docID,
		"_rev":     rev,
		"_deleted": true,
	}, nil)
}

func (d *db) Stats(_ context.Context) (*driver.DBStats, error) {
	return &driver.DBStats{
		Name: d.dbName,
		// DocCount:     0,
		// DeletedCount: 0,
		// UpdateSeq:    "",
		// DiskSize:     0,
		// ActiveSize:   0,
		// ExternalSize: 0,
	}, nil
}

func (c *client) Compact(_ context.Context) error {
	// FIXME: Unimplemented
	return notYetImplemented
}

func (d *db) CompactView(_ context.Context, _ string) error {
	// FIXME: Unimplemented
	return notYetImplemented
}

func (d *db) ViewCleanup(_ context.Context) error {
	// FIXME: Unimplemented
	return notYetImplemented
}

func (d *db) Changes(context.Context, driver.Options) (driver.Changes, error) {
	// FIXME: Unimplemented
	return nil, notYetImplemented
}

func (d *db) PutAttachment(context.Context, string, *driver.Attachment, driver.Options) (string, error) {
	// FIXME: Unimplemented
	return "", notYetImplemented
}

func (d *db) GetAttachment(context.Context, string, string, driver.Options) (*driver.Attachment, error) {
	// FIXME: Unimplemented
	return nil, notYetImplemented
}

func (d *db) DeleteAttachment(context.Context, string, string, driver.Options) (newRev string, err error) {
	// FIXME: Unimplemented
	return "", notYetImplemented
}

func (d *db) Close() error { return nil }