package generic

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/Rican7/retry/backoff"
	"github.com/Rican7/retry/strategy"
	"github.com/k3s-io/kine/pkg/server"
	"github.com/sirupsen/logrus"
)

const (
	defaultMaxIdleConns = 2 // copied from database/sql
)

// explicit interface check
var _ server.Dialect = (*Generic)(nil)

var (
	columns = "kv.id AS theid, kv.name, kv.created, kv.deleted, kv.create_revision, kv.prev_revision, kv.lease, kv.value, kv.old_value"
	revSQL  = `
		SELECT MAX(rkv.id) AS id
		FROM kine AS rkv`

	compactRevSQL = `
		SELECT MAX(crkv.prev_revision) AS prev_revision
		FROM kine AS crkv
		WHERE crkv.name = 'compact_rev_key'`

	idOfKey = `
		AND
		mkv.id <= ? AND
		mkv.id > (
			SELECT MAX(ikv.id) AS id
			FROM kine AS ikv
			WHERE
				ikv.name = ? AND
				ikv.id <= ?)`

	listSQL = fmt.Sprintf(`
		SELECT (%s), (%s), %s
		FROM kine AS kv
		JOIN (
			SELECT MAX(mkv.id) AS id
			FROM kine AS mkv
			WHERE
				mkv.name LIKE ?
				%%s
			GROUP BY mkv.name) maxkv
	    ON maxkv.id = kv.id
		WHERE
			  (kv.deleted = 0 OR ?)
		ORDER BY kv.id ASC
		`, revSQL, compactRevSQL, columns)
)

type Stripped string

func (s Stripped) String() string {
	str := strings.ReplaceAll(string(s), "\n", "")
	return regexp.MustCompile("[\t ]+").ReplaceAllString(str, " ")
}

type ErrRetry func(error) bool
type TranslateErr func(error) error

type ConnectionPoolConfig struct {
	MaxIdle     int           // zero means defaultMaxIdleConns; negative means 0
	MaxOpen     int           // <= 0 means unlimited
	MaxLifetime time.Duration // maximum amount of time a connection may be reused
}

type Generic struct {
	sync.Mutex

	LockWrites            bool
	LastInsertID          bool
	DB                    *sql.DB
	GetCurrentSQL         string
	GetRevisionSQL        string
	RevisionSQL           string
	ListRevisionStartSQL  string
	GetRevisionAfterSQL   string
	CountSQL              string
	AfterSQL              string
	DeleteSQL             string
	CompactSQL            string
	UpdateCompactSQL      string
	InsertSQL             string
	FillSQL               string
	InsertLastInsertIDSQL string
	GetSizeSQL            string
	Retry                 ErrRetry
	TranslateErr          TranslateErr
}

func q(sql, param string, numbered bool) string {
	if param == "?" && !numbered {
		return sql
	}

	regex := regexp.MustCompile(`\?`)
	n := 0
	return regex.ReplaceAllStringFunc(sql, func(string) string {
		if numbered {
			n++
			return param + strconv.Itoa(n)
		}
		return param
	})
}

func (d *Generic) Migrate(ctx context.Context) {
	var (
		count     = 0
		countKV   = d.queryRow(ctx, "SELECT COUNT(*) FROM key_value")
		countKine = d.queryRow(ctx, "SELECT COUNT(*) FROM kine")
	)

	if err := countKV.Scan(&count); err != nil || count == 0 {
		return
	}

	if err := countKine.Scan(&count); err != nil || count != 0 {
		return
	}

	logrus.Infof("Migrating content from old table")
	_, err := d.execute(ctx,
		`INSERT INTO kine(deleted, create_revision, prev_revision, name, value, created, lease)
					SELECT 0, 0, 0, kv.name, kv.value, 1, CASE WHEN kv.ttl > 0 THEN 15 ELSE 0 END
					FROM key_value kv
						WHERE kv.id IN (SELECT MAX(kvd.id) FROM key_value kvd GROUP BY kvd.name)`)
	if err != nil {
		logrus.Errorf("Migration failed: %v", err)
	}
}

func configureConnectionPooling(connPoolConfig ConnectionPoolConfig, db *sql.DB, driverName string) {
	// behavior copied from database/sql - zero means defaultMaxIdleConns; negative means 0
	if connPoolConfig.MaxIdle < 0 {
		connPoolConfig.MaxIdle = 0
	} else if connPoolConfig.MaxIdle == 0 {
		connPoolConfig.MaxIdle = defaultMaxIdleConns
	}

	logrus.Infof("Configuring %s database connection pooling: maxIdleConns=%d, maxOpenConns=%d, connMaxLifetime=%s", driverName, connPoolConfig.MaxIdle, connPoolConfig.MaxOpen, connPoolConfig.MaxLifetime)
	db.SetMaxIdleConns(connPoolConfig.MaxIdle)
	db.SetMaxOpenConns(connPoolConfig.MaxOpen)
	db.SetConnMaxLifetime(connPoolConfig.MaxLifetime)
}

func openAndTest(driverName, dataSourceName string) (*sql.DB, error) {
	db, err := sql.Open(driverName, dataSourceName)
	if err != nil {
		return nil, err
	}

	for i := 0; i < 3; i++ {
		if err := db.Ping(); err != nil {
			db.Close()
			return nil, err
		}
	}

	return db, nil
}

func Open(ctx context.Context, driverName, dataSourceName string, connPoolConfig ConnectionPoolConfig, paramCharacter string, numbered bool) (*Generic, error) {
	var (
		db  *sql.DB
		err error
	)

	for i := 0; i < 300; i++ {
		db, err = openAndTest(driverName, dataSourceName)
		if err == nil {
			break
		}

		logrus.Errorf("failed to ping connection: %v", err)
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		case <-time.After(time.Second):
		}
	}

	configureConnectionPooling(connPoolConfig, db, driverName)

	return &Generic{
		DB: db,

		GetRevisionSQL: q(fmt.Sprintf(`
			SELECT
			0, 0, %s
			FROM kine AS kv
			WHERE kv.id = ?`, columns), paramCharacter, numbered),

		GetCurrentSQL:        q(fmt.Sprintf(listSQL, ""), paramCharacter, numbered),
		ListRevisionStartSQL: q(fmt.Sprintf(listSQL, "AND mkv.id <= ?"), paramCharacter, numbered),
		GetRevisionAfterSQL:  q(fmt.Sprintf(listSQL, idOfKey), paramCharacter, numbered),

		CountSQL: q(fmt.Sprintf(`
			SELECT (%s), COUNT(c.theid)
			FROM (
				%s
			) c`, revSQL, fmt.Sprintf(listSQL, "")), paramCharacter, numbered),

		AfterSQL: q(fmt.Sprintf(`
			SELECT (%s), (%s), %s
			FROM kine AS kv
			WHERE
				kv.name LIKE ? AND
				kv.id > ?
			ORDER BY kv.id ASC`, revSQL, compactRevSQL, columns), paramCharacter, numbered),

		DeleteSQL: q(`
			DELETE FROM kine AS kv
			WHERE kv.id = ?`, paramCharacter, numbered),

		UpdateCompactSQL: q(`
			UPDATE kine
			SET prev_revision = ?
			WHERE name = 'compact_rev_key'`, paramCharacter, numbered),

		InsertLastInsertIDSQL: q(`INSERT INTO kine(name, created, deleted, create_revision, prev_revision, lease, value, old_value)
			values(?, ?, ?, ?, ?, ?, ?, ?)`, paramCharacter, numbered),

		InsertSQL: q(`INSERT INTO kine(name, created, deleted, create_revision, prev_revision, lease, value, old_value)
			values(?, ?, ?, ?, ?, ?, ?, ?) RETURNING id`, paramCharacter, numbered),

		FillSQL: q(`INSERT INTO kine(id, name, created, deleted, create_revision, prev_revision, lease, value, old_value)
			values(?, ?, ?, ?, ?, ?, ?, ?, ?)`, paramCharacter, numbered),
	}, err
}

func (d *Generic) query(ctx context.Context, sql string, args ...interface{}) (*sql.Rows, error) {
	logrus.Tracef("QUERY %v : %s", args, Stripped(sql))
	return d.DB.QueryContext(ctx, sql, args...)
}

func (d *Generic) queryRow(ctx context.Context, sql string, args ...interface{}) *sql.Row {
	logrus.Tracef("QUERY ROW %v : %s", args, Stripped(sql))
	return d.DB.QueryRowContext(ctx, sql, args...)
}

func (d *Generic) execute(ctx context.Context, sql string, args ...interface{}) (result sql.Result, err error) {
	if d.LockWrites {
		d.Lock()
		defer d.Unlock()
	}

	wait := strategy.Backoff(backoff.Linear(100 + time.Millisecond))
	for i := uint(0); i < 20; i++ {
		logrus.Tracef("EXEC (try: %d) %v : %s", i, args, Stripped(sql))
		result, err = d.DB.ExecContext(ctx, sql, args...)
		if err != nil && d.Retry != nil && d.Retry(err) {
			wait(i)
			continue
		}
		return result, err
	}
	return
}

func (d *Generic) GetCompactRevision(ctx context.Context) (int64, error) {
	var id int64
	row := d.queryRow(ctx, compactRevSQL)
	err := row.Scan(&id)
	if err == sql.ErrNoRows {
		return 0, nil
	}
	return id, err
}

func (d *Generic) SetCompactRevision(ctx context.Context, revision int64) error {
	logrus.Tracef("SETCOMPACTREVISION %v", revision)
	_, err := d.execute(ctx, d.UpdateCompactSQL, revision)
	return err
}

func (d *Generic) Compact(ctx context.Context, revision int64) (int64, error) {
	logrus.Tracef("COMPACT %v", revision)
	res, err := d.execute(ctx, d.CompactSQL, revision, revision)
	if err != nil {
		return 0, err
	}
	return res.RowsAffected()
}

func (d *Generic) GetRevision(ctx context.Context, revision int64) (*sql.Rows, error) {
	return d.query(ctx, d.GetRevisionSQL, revision)
}

func (d *Generic) DeleteRevision(ctx context.Context, revision int64) error {
	logrus.Tracef("DELETEREVISION %v", revision)
	_, err := d.execute(ctx, d.DeleteSQL, revision)
	return err
}

func (d *Generic) ListCurrent(ctx context.Context, prefix string, limit int64, includeDeleted bool) (*sql.Rows, error) {
	sql := d.GetCurrentSQL
	if limit > 0 {
		sql = fmt.Sprintf("%s LIMIT %d", sql, limit)
	}
	return d.query(ctx, sql, prefix, includeDeleted)
}

func (d *Generic) List(ctx context.Context, prefix, startKey string, limit, revision int64, includeDeleted bool) (*sql.Rows, error) {
	if startKey == "" {
		sql := d.ListRevisionStartSQL
		if limit > 0 {
			sql = fmt.Sprintf("%s LIMIT %d", sql, limit)
		}
		return d.query(ctx, sql, prefix, revision, includeDeleted)
	}

	sql := d.GetRevisionAfterSQL
	if limit > 0 {
		sql = fmt.Sprintf("%s LIMIT %d", sql, limit)
	}
	return d.query(ctx, sql, prefix, revision, startKey, revision, includeDeleted)
}

func (d *Generic) Count(ctx context.Context, prefix string) (int64, int64, error) {
	var (
		rev sql.NullInt64
		id  int64
	)

	row := d.queryRow(ctx, d.CountSQL, prefix, false)
	err := row.Scan(&rev, &id)
	return rev.Int64, id, err
}

func (d *Generic) CurrentRevision(ctx context.Context) (int64, error) {
	var id int64
	row := d.queryRow(ctx, revSQL)
	err := row.Scan(&id)
	if err == sql.ErrNoRows {
		return 0, nil
	}
	return id, err
}

func (d *Generic) After(ctx context.Context, prefix string, rev, limit int64) (*sql.Rows, error) {
	sql := d.AfterSQL
	if limit > 0 {
		sql = fmt.Sprintf("%s LIMIT %d", sql, limit)
	}
	return d.query(ctx, sql, prefix, rev)
}

func (d *Generic) Fill(ctx context.Context, revision int64) error {
	_, err := d.execute(ctx, d.FillSQL, revision, fmt.Sprintf("gap-%d", revision), 0, 1, 0, 0, 0, nil, nil)
	return err
}

func (d *Generic) IsFill(key string) bool {
	return strings.HasPrefix(key, "gap-")
}

func (d *Generic) Insert(ctx context.Context, key string, create, delete bool, createRevision, previousRevision int64, ttl int64, value, prevValue []byte) (id int64, err error) {
	if d.TranslateErr != nil {
		defer func() {
			if err != nil {
				err = d.TranslateErr(err)
			}
		}()
	}

	cVal := 0
	dVal := 0
	if create {
		cVal = 1
	}
	if delete {
		dVal = 1
	}

	if d.LastInsertID {
		row, err := d.execute(ctx, d.InsertLastInsertIDSQL, key, cVal, dVal, createRevision, previousRevision, ttl, value, prevValue)
		if err != nil {
			return 0, err
		}
		return row.LastInsertId()
	}

	row := d.queryRow(ctx, d.InsertSQL, key, cVal, dVal, createRevision, previousRevision, ttl, value, prevValue)
	err = row.Scan(&id)
	return id, err
}

func (d *Generic) GetSize(ctx context.Context) (int64, error) {
	if d.GetSizeSQL == "" {
		return 0, errors.New("driver does not support size reporting")
	}
	var size int64
	row := d.queryRow(ctx, d.GetSizeSQL)
	if err := row.Scan(&size); err != nil {
		return 0, err
	}
	return size, nil
}