package db

import (
	"context"
	"database/sql"
	"fmt"
	"io/ioutil"
	"regexp"
	"sort"
	"time"

	"git.example.com/example/goserv/assets/configfs"
	"github.com/jmoiron/sqlx"

	// pq injects itself into sql as 'postgres'
	_ "github.com/lib/pq"
)

// DB is a concurrency-safe db connection instance
var DB *sqlx.DB
var firstDBURL PleaseDoubleCheckTheDatabaseURLDontDropProd

// Init initializes the database
func Init(pgURL string) error {
	// https://godoc.org/github.com/lib/pq

	firstDBURL = PleaseDoubleCheckTheDatabaseURLDontDropProd(pgURL)
	dbtype := "postgres"

	ctx, done := context.WithDeadline(context.Background(), time.Now().Add(5*time.Second))
	defer done()
	db, err := sql.Open(dbtype, pgURL)
	if err := db.PingContext(ctx); nil != err {
		return err
	}

	// basic stuff
	f, err := configfs.Assets.Open("./postgres/init.sql")
	if nil != err {
		return err
	}
	sqlBytes, err := ioutil.ReadAll(f)
	if nil != err {
		return err
	}
	if _, err := db.ExecContext(ctx, string(sqlBytes)); nil != err {
		return err
	}

	// project-specific stuff
	f, err = configfs.Assets.Open("./postgres/tables.sql")
	if nil != err {
		return err
	}
	sqlBytes, err = ioutil.ReadAll(f)
	if nil != err {
		return err
	}
	if _, err := db.ExecContext(ctx, string(sqlBytes)); nil != err {
		return err
	}

	DB = sqlx.NewDb(db, dbtype)

	return nil
}

// PleaseDoubleCheckTheDatabaseURLDontDropProd is just a friendly,
// hopefully helpful reminder, not to only use this in test files,
// and to not drop the production database
type PleaseDoubleCheckTheDatabaseURLDontDropProd string

// DropAllTables runs drop.sql, which is intended only for tests
func DropAllTables(dbURL PleaseDoubleCheckTheDatabaseURLDontDropProd) error {
	if err := CanDropAllTables(string(dbURL)); nil != err {
		return err
	}

	// drop stuff
	f, err := configfs.Assets.Open("./postgres/drop.sql")
	if nil != err {
		return err
	}
	sqlBytes, err := ioutil.ReadAll(f)
	if nil != err {
		return err
	}
	ctx, done := context.WithDeadline(context.Background(), time.Now().Add(1*time.Second))
	defer done()
	if _, err := DB.ExecContext(ctx, string(sqlBytes)); nil != err {
		return err
	}

	return nil
}

// CanDropAllTables returns an error if the dbURL does not contain the words "test" or
// "demo" at a letter boundary
func CanDropAllTables(dbURL string) error {
	var isDemo bool
	nonalpha := regexp.MustCompile(`[^a-zA-Z]`)
	haystack := nonalpha.Split(dbURL, -1)
	sort.Strings(haystack)
	for _, needle := range []string{"test", "demo"} {
		// the index to insert x if x is not present (it could be len(a))
		// (meaning that it is the index at which it exists, if it exists)
		i := sort.SearchStrings(haystack, needle)
		if i < len(haystack) && haystack[i] == needle {
			isDemo = true
			break
		}
	}
	if isDemo {
		return nil
	}
	return fmt.Errorf(
		"test and demo database URLs must contain the word 'test' or 'demo' "+
			"separated by a non-alphabet character, such as /test2/db_demo1\n%q\n",
		dbURL,
	)
}