package mysql

import (
	"bytes"
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"net/url"

	"github.com/Sirupsen/logrus"
	"github.com/go-sql-driver/mysql"
	_ "github.com/go-sql-driver/mysql"
	"github.com/iron-io/functions/api/datastore/internal/datastoreutil"
	"github.com/iron-io/functions/api/models"
)

const routesTableCreate = `CREATE TABLE IF NOT EXISTS routes (
	app_name varchar(256) NOT NULL,
	path varchar(256) NOT NULL,
	image varchar(256) NOT NULL,
	format varchar(16) NOT NULL,
	maxc int NOT NULL,
	memory int NOT NULL,
	timeout int NOT NULL,
	type varchar(16) NOT NULL,
	headers text NOT NULL,
	config text NOT NULL,
	PRIMARY KEY (app_name, path)
);`

const appsTableCreate = `CREATE TABLE IF NOT EXISTS apps (
    name varchar(256) NOT NULL PRIMARY KEY,
	config text NOT NULL
);`

const extrasTableCreate = `CREATE TABLE IF NOT EXISTS extras (
    id varchar(256) NOT NULL PRIMARY KEY,
	value varchar(256) NOT NULL
);`

const routeSelector = `SELECT app_name, path, image, format, maxc, memory, type, timeout, headers, config FROM routes`

type rowScanner interface {
	Scan(dest ...interface{}) error
}

type rowQuerier interface {
	QueryRow(query string, args ...interface{}) *sql.Row
}

/*
MySQLDatastore defines a basic MySQL Datastore struct.
*/
type MySQLDatastore struct {
	db *sql.DB
}

/*
New creates a new MySQL Datastore.
*/
func New(url *url.URL) (models.Datastore, error) {
	u := fmt.Sprintf("%s@%s%s", url.User.String(), url.Host, url.Path)
	db, err := sql.Open("mysql", u)
	if err != nil {
		return nil, err
	}

	err = db.Ping()
	if err != nil {
		return nil, err
	}

	maxIdleConns := 30
	db.SetMaxIdleConns(maxIdleConns)
	logrus.WithFields(logrus.Fields{"max_idle_connections": maxIdleConns}).Info("MySQL dialed")

	pg := &MySQLDatastore{
		db: db,
	}

	for _, v := range []string{routesTableCreate, appsTableCreate, extrasTableCreate} {
		_, err = db.Exec(v)
		if err != nil {
			return nil, err
		}
	}

	return datastoreutil.NewValidator(pg), nil
}

/*
InsertApp inserts an app to MySQL.
*/
func (ds *MySQLDatastore) InsertApp(ctx context.Context, app *models.App) (*models.App, error) {
	var cbyte []byte
	var err error

	if app.Config != nil {
		cbyte, err = json.Marshal(app.Config)
		if err != nil {
			return nil, err
		}
	}
	stmt, err := ds.db.Prepare("INSERT apps SET name=?,config=?")

	if err != nil {
		return nil, err
	}

	_, err = stmt.Exec(app.Name, string(cbyte))

	if err != nil {
		mysqlErr := err.(*mysql.MySQLError)
		if mysqlErr.Number == 1062 {
			return nil, models.ErrAppsAlreadyExists
		}
		return nil, err
	}

	return app, nil
}

/*
UpdateApp updates an existing app on MySQL.
*/
func (ds *MySQLDatastore) UpdateApp(ctx context.Context, newapp *models.App) (*models.App, error) {
	app := &models.App{Name: newapp.Name}
	err := ds.Tx(func(tx *sql.Tx) error {
		row := ds.db.QueryRow(`SELECT config FROM apps WHERE name=?`, app.Name)

		var config string
		if err := row.Scan(&config); err != nil {
			if err == sql.ErrNoRows {
				return models.ErrAppsNotFound
			}
			return err
		}

		if config != "" {
			err := json.Unmarshal([]byte(config), &app.Config)
			if err != nil {
				return err
			}
		}

		app.UpdateConfig(newapp.Config)

		cbyte, err := json.Marshal(app.Config)
		if err != nil {
			return err
		}

		stmt, err := ds.db.Prepare(`UPDATE apps SET config=? WHERE name=?`)

		if err != nil {
			return err
		}

		res, err := stmt.Exec(string(cbyte), app.Name)

		if err != nil {
			return err
		}

		if n, err := res.RowsAffected(); err != nil {
			return err
		} else if n == 0 {
			return models.ErrAppsNotFound
		}
		return nil
	})

	if err != nil {
		return nil, err
	}

	return app, nil
}

/*
RemoveApp removes an existing app on MySQL.
*/
func (ds *MySQLDatastore) RemoveApp(ctx context.Context, appName string) error {
	_, err := ds.db.Exec(`
	  DELETE FROM apps
	  WHERE name = ?
	`, appName)

	if err != nil {
		return err
	}

	return nil
}

/*
GetApp retrieves an app from MySQL.
*/
func (ds *MySQLDatastore) GetApp(ctx context.Context, name string) (*models.App, error) {
	row := ds.db.QueryRow(`SELECT name, config FROM apps WHERE name=?`, name)

	var resName string
	var config string
	err := row.Scan(&resName, &config)

	res := &models.App{
		Name: resName,
	}

	json.Unmarshal([]byte(config), &res.Config)

	if err != nil {
		if err == sql.ErrNoRows {
			return nil, models.ErrAppsNotFound
		}
		return nil, err
	}

	return res, nil
}

func scanApp(scanner rowScanner, app *models.App) error {
	var configStr string

	err := scanner.Scan(
		&app.Name,
		&configStr,
	)

	json.Unmarshal([]byte(configStr), &app.Config)

	return err
}

/*
GetApps retrieves an array of apps according to a specific filter.
*/
func (ds *MySQLDatastore) GetApps(ctx context.Context, filter *models.AppFilter) ([]*models.App, error) {
	res := []*models.App{}
	filterQuery, args := buildFilterAppQuery(filter)
	rows, err := ds.db.Query(fmt.Sprintf("SELECT DISTINCT name, config FROM apps %s", filterQuery), args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var app models.App
		err := scanApp(rows, &app)

		if err != nil {
			break
		}
		res = append(res, &app)
	}

	if err := rows.Err(); err != nil {
		return res, err
	}
	return res, nil
}

/*
InsertRoute inserts an route to MySQL.
*/
func (ds *MySQLDatastore) InsertRoute(ctx context.Context, route *models.Route) (*models.Route, error) {
	hbyte, err := json.Marshal(route.Headers)
	if err != nil {
		return nil, err
	}

	cbyte, err := json.Marshal(route.Config)
	if err != nil {
		return nil, err
	}

	err = ds.Tx(func(tx *sql.Tx) error {
		r := tx.QueryRow(`SELECT 1 FROM apps WHERE name=?`, route.AppName)
		if err := r.Scan(new(int)); err != nil {
			if err == sql.ErrNoRows {
				return models.ErrAppsNotFound
			}
		}
		same, err := tx.Query(`SELECT 1 FROM routes WHERE app_name=? AND path=?`,
			route.AppName, route.Path)
		if err != nil {
			return err
		}
		defer same.Close()
		if same.Next() {
			return models.ErrRoutesAlreadyExists
		}

		_, err = tx.Exec(`
		INSERT INTO routes (
			app_name,
			path,
			image,
			format,
			maxc,
			memory,
			type,
			timeout,
			headers,
			config
		)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?);`,
			route.AppName,
			route.Path,
			route.Image,
			route.Format,
			route.MaxConcurrency,
			route.Memory,
			route.Type,
			route.Timeout,
			string(hbyte),
			string(cbyte),
		)
		return err
	})

	if err != nil {
		return nil, err
	}
	return route, nil
}

/*
UpdateRoute updates an existing route on MySQL.
*/
func (ds *MySQLDatastore) UpdateRoute(ctx context.Context, newroute *models.Route) (*models.Route, error) {
	var route models.Route
	err := ds.Tx(func(tx *sql.Tx) error {
		row := ds.db.QueryRow(fmt.Sprintf("%s WHERE app_name=? AND path=?", routeSelector), newroute.AppName, newroute.Path)
		if err := scanRoute(row, &route); err == sql.ErrNoRows {
			return models.ErrRoutesNotFound
		} else if err != nil {
			return err
		}

		route.Update(newroute)

		hbyte, err := json.Marshal(route.Headers)
		if err != nil {
			return err
		}

		cbyte, err := json.Marshal(route.Config)
		if err != nil {
			return err
		}

		res, err := tx.Exec(`
		UPDATE routes SET
			image = ?,
			format = ?,
			maxc = ?,
			memory = ?,
			type = ?,
			timeout = ?,
			headers = ?,
			config = ?
		WHERE app_name = ? AND path = ?;`,
			route.Image,
			route.Format,
			route.MaxConcurrency,
			route.Memory,
			route.Type,
			route.Timeout,
			string(hbyte),
			string(cbyte),
			route.AppName,
			route.Path,
		)

		if err != nil {
			return err
		}

		if n, err := res.RowsAffected(); err != nil {
			return err
		} else if n == 0 {
			return models.ErrRoutesNotFound
		}

		return nil
	})

	if err != nil {
		return nil, err
	}
	return &route, nil
}

/*
RemoveRoute removes an existing route on MySQL.
*/
func (ds *MySQLDatastore) RemoveRoute(ctx context.Context, appName, routePath string) error {
	res, err := ds.db.Exec(`
		DELETE FROM routes
		WHERE path = ? AND app_name = ?
	`, routePath, appName)

	if err != nil {
		return err
	}

	n, err := res.RowsAffected()
	if err != nil {
		return err
	}

	if n == 0 {
		return models.ErrRoutesRemoving
	}

	return nil
}

func scanRoute(scanner rowScanner, route *models.Route) error {
	var headerStr string
	var configStr string

	err := scanner.Scan(
		&route.AppName,
		&route.Path,
		&route.Image,
		&route.Format,
		&route.MaxConcurrency,
		&route.Memory,
		&route.Type,
		&route.Timeout,
		&headerStr,
		&configStr,
	)
	if err != nil {
		return err
	}

	if headerStr == "" {
		return models.ErrRoutesNotFound
	}

	if err := json.Unmarshal([]byte(headerStr), &route.Headers); err != nil {
		return err
	}
	return json.Unmarshal([]byte(configStr), &route.Config)
}

/*
GetRoute retrieves a route from MySQL.
*/
func (ds *MySQLDatastore) GetRoute(ctx context.Context, appName, routePath string) (*models.Route, error) {
	var route models.Route

	row := ds.db.QueryRow(fmt.Sprintf("%s WHERE app_name=? AND path=?", routeSelector), appName, routePath)
	err := scanRoute(row, &route)

	if err == sql.ErrNoRows {
		return nil, models.ErrRoutesNotFound
	} else if err != nil {
		return nil, err
	}
	return &route, nil
}

/*
GetRoutes retrieves an array of routes according to a specific filter.
*/
func (ds *MySQLDatastore) GetRoutes(ctx context.Context, filter *models.RouteFilter) ([]*models.Route, error) {
	res := []*models.Route{}
	filterQuery, args := buildFilterRouteQuery(filter)
	rows, err := ds.db.Query(fmt.Sprintf("%s %s", routeSelector, filterQuery), args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var route models.Route
		err := scanRoute(rows, &route)
		if err != nil {
			continue
		}
		res = append(res, &route)

	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return res, nil
}

/*
GetRoutesByApp retrieves a route with a specific app name.
*/
func (ds *MySQLDatastore) GetRoutesByApp(ctx context.Context, appName string, filter *models.RouteFilter) ([]*models.Route, error) {
	res := []*models.Route{}

	var filterQuery string
	var args []interface{}
	if filter == nil {
		filterQuery = "WHERE app_name = ?"
		args = []interface{}{appName}
	} else {
		filter.AppName = appName
		filterQuery, args = buildFilterRouteQuery(filter)
	}
	rows, err := ds.db.Query(fmt.Sprintf("%s %s", routeSelector, filterQuery), args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var route models.Route
		err := scanRoute(rows, &route)
		if err != nil {
			continue
		}
		res = append(res, &route)

	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	return res, nil
}

func buildFilterAppQuery(filter *models.AppFilter) (string, []interface{}) {
	if filter == nil {
		return "", nil
	}

	if filter.Name != "" {
		return "WHERE name LIKE ?", []interface{}{filter.Name}
	}

	return "", nil
}

func buildFilterRouteQuery(filter *models.RouteFilter) (string, []interface{}) {
	if filter == nil {
		return "", nil
	}
	var b bytes.Buffer
	var args []interface{}

	where := func(colOp, val string) {
		if val != "" {
			args = append(args, val)
			if len(args) == 1 {
				fmt.Fprintf(&b, "WHERE %s ?", colOp)
			} else {
				fmt.Fprintf(&b, " AND %s ?", colOp)
			}
		}
	}

	where("path =", filter.Path)
	where("app_name =", filter.AppName)
	where("image =", filter.Image)

	return b.String(), args
}

/*
Put inserts an extra into MySQL.
*/
func (ds *MySQLDatastore) Put(ctx context.Context, key, value []byte) error {
	_, err := ds.db.Exec(`
	    INSERT INTO extras (
			id,
			value
		)
		VALUES (?, ?)
		ON DUPLICATE KEY UPDATE
			value = ?
		`, string(key), string(value), string(value))

	if err != nil {
		return err
	}

	return nil
}

/*
Get retrieves the value of a specific extra from MySQL.
*/
func (ds *MySQLDatastore) Get(ctx context.Context, key []byte) ([]byte, error) {
	row := ds.db.QueryRow("SELECT value FROM extras WHERE id=?", key)

	var value string
	err := row.Scan(&value)
	if err == sql.ErrNoRows {
		return nil, nil
	} else if err != nil {
		return nil, err
	}

	return []byte(value), nil
}

/*
Tx Begins and commits a MySQL Transaction.
*/
func (ds *MySQLDatastore) Tx(f func(*sql.Tx) error) error {
	tx, err := ds.db.Begin()
	if err != nil {
		return err
	}
	err = f(tx)
	if err != nil {
		tx.Rollback()
		return err
	}
	return tx.Commit()
}