package db0305

import (
	"encoding/json"
	"errors"
)

type DB struct {
	KV     KV
	tables map[string]Schema
}

func (db *DB) Open() error {
	db.tables = map[string]Schema{}
	return db.KV.Open()
}

func (db *DB) Close() error { return db.KV.Close() }

func (db *DB) Select(schema *Schema, row Row) (ok bool, err error) {
	key := row.EncodeKey(schema)
	val, ok, err := db.KV.Get(key)
	if err != nil || !ok {
		return ok, err
	}
	if err = row.DecodeVal(schema, val); err != nil {
		return false, err
	}
	return true, nil
}

func (db *DB) Insert(schema *Schema, row Row) (updated bool, err error) {
	key := row.EncodeKey(schema)
	val := row.EncodeVal(schema)
	return db.KV.SetEx(key, val, ModeInsert)
}

func (db *DB) Upsert(schema *Schema, row Row) (updated bool, err error) {
	key := row.EncodeKey(schema)
	val := row.EncodeVal(schema)
	return db.KV.SetEx(key, val, ModeUpsert)
}

func (db *DB) Update(schema *Schema, row Row) (updated bool, err error) {
	key := row.EncodeKey(schema)
	val := row.EncodeVal(schema)
	return db.KV.SetEx(key, val, ModeUpdate)
}

func (db *DB) Delete(schema *Schema, row Row) (deleted bool, err error) {
	key := row.EncodeKey(schema)
	return db.KV.Del(key)
}

type SQLResult struct {
	Updated int
	Header  []string
	Values  []Row
}

func (db *DB) ExecStmt(stmt interface{}) (r SQLResult, err error) {
	switch ptr := stmt.(type) {
	case *StmtCreatTable:
		err = db.execCreateTable(ptr)
	case *StmtSelect:
		r.Header = ptr.cols
		r.Values, err = db.execSelect(ptr)
	case *StmtInsert:
		r.Updated, err = db.execInsert(ptr)
	case *StmtUpdate:
		r.Updated, err = db.execUpdate(ptr)
	case *StmtDelete:
		r.Updated, err = db.execDelete(ptr)
	default:
		panic("unreachable")
	}
	return
}

func (db *DB) execCreateTable(stmt *StmtCreatTable) (err error)

func (db *DB) GetSchema(table string) (Schema, error) {
	schema, ok := db.tables[table]
	if !ok {
		val, ok, err := db.KV.Get([]byte("@schema_" + table))
		if err == nil && ok {
			err = json.Unmarshal(val, &schema)
		}
		if err != nil {
			return Schema{}, err
		}
		if !ok {
			return Schema{}, errors.New("table is not found")
		}
		db.tables[table] = schema
	}
	return schema, nil
}

func (db *DB) execSelect(stmt *StmtSelect) ([]Row, error)

func (db *DB) execInsert(stmt *StmtInsert) (count int, err error)

func (db *DB) execUpdate(stmt *StmtUpdate) (count int, err error)

func (db *DB) execDelete(stmt *StmtDelete) (count int, err error)

// QzBQWVJJOUhU https://trialofcode.org/