package boltdb

import (
        "encoding/json"
        "errors"
        "time"

        "go.etcd.io/bbolt"
)

// Generic error results
var (
        ErrNoResults        = errors.New("no results found") // ErrNoResults indicates query found no results
        ErrInvalidTableName = errors.New("invalid table")    // ErrInvalidTableName indicates that specified table does not exist
        ErrNoConnection     = errors.New("no db connection") //
        ErrExists           = errors.New("key existss")
        db                  *bbolt.DB
)

// Initialize sets up bbolt db using file path and creates tables if required
func Initialize(file string, tables []string) error {
        var err error
        db, err = bbolt.Open(file, 0666, &bbolt.Options{Timeout: 1 * time.Second})
        if err != nil {
                return err
        }
        return createTables(tables)
}

// Close closes the database
func Close() error {
        return db.Close()
}

// Connection returns the connection to the store for more advanced queries by caller
func Connection() *bbolt.DB {
        return db
}

func createTables(tables []string) error {
        var errs error
        for _, table := range tables {
                if err := createTable(table); err != nil {
                        errs = errors.Join(errs, err)
                }
        }
        return errs
}

func createTable(name string) error {
        if err := db.Update(func(tx *bbolt.Tx) error {
                if _, err := tx.CreateBucketIfNotExists([]byte(name)); err != nil {
                        return err
                }
                return nil
        }); err != nil {
                return err
        }
        return nil
}

// Save saves a value under key in the specified table
func Save(value any, key, table string) error {
        marshalled, err := json.Marshal(&value)
        if err != nil {
                return err
        }
        return db.Update(func(tx *bbolt.Tx) error {
                b := tx.Bucket([]byte(table))
                if b == nil {
                        return ErrInvalidTableName
                }
                return b.Put([]byte(key), marshalled)
        })
}

// Insert saves a value only if key does not exist
func Insert(value any, key, table string) error {
        _, err := Get[any](key, table)
        if err == nil {
                return ErrExists
        }
        if errors.Is(err, ErrNoResults) {
                return Save(value, key, table)
        }
        return err
}

// Update save a value only if key already exists
func Update(value any, key, table string) error {
        _, err := Get[any](key, table)
        if err == nil {
                return Save(value, key, table)
        }
        return ErrExists
}

// Get retrieves a value for key in specified table
func Get[T any](key, table string) (T, error) {
        var value T
        err := db.View(func(tx *bbolt.Tx) error {
                b := tx.Bucket([]byte(table))
                if b == nil {
                        return ErrInvalidTableName
                }
                v := b.Get([]byte(key))
                if v == nil {
                        return ErrNoResults
                }
                if err := json.Unmarshal(v, &value); err != nil {
                        return err
                }
                return nil
        })
        return value, err
}

// GetAll retrieves all values from table
func GetAll[T any](table string) ([]T, error) {
        var values []T
        err := db.View(func(tx *bbolt.Tx) error {
                b := tx.Bucket([]byte(table))
                if b == nil {
                        return ErrInvalidTableName
                }
                _ = b.ForEach(func(k, v []byte) error {
                        var value T
                        if err := json.Unmarshal(v, &value); err != nil {
                                return err
                        }
                        values = append(values, value)
                        return nil
                })
                return nil
        })
        return values, err
}

// Delete deletes the entry in table corresponding to key
func Delete[T any](key, table string) error {
        //verify table exists
        if _, err := Get[T](key, table); err != nil {
                return err
        }
        err := db.Update(func(tx *bbolt.Tx) error {
                return tx.Bucket([]byte(table)).Delete([]byte(key))
        })
        return err
}