package kvrepl

import "fmt"

// DB is struct defining two maps, pkv (points to kv) and nest, which
// aids figuring out how nested the commits are for current transaction
type DB struct {
	KV1  map[string]string
	KV2  map[string]string
	PKV  bool
	nest int
}

// read reads a key out of a map and checks for parsing errors
func read(args []string, kv map[string]string) (string, error) {
	if len(args) != 1 {
		return "", fmt.Errorf("incorrect usage: READ <key>")
	}
	i, ok := kv[args[0]]
	if !ok {
		return "", fmt.Errorf("key does not exist")
	}
	return i, nil
}

// write writes key/value to map and checks for parsing errors
func write(args []string, kv map[string]string) error {
	if len(args) != 2 {
		return fmt.Errorf("incorrect usage: WRITE <key> <value>")
	}
	kv[args[0]] = args[1]
	return nil
}

// del deletes a key from map and checks for parsing errors
func del(args []string, kv map[string]string) error {
	if len(args) != 1 {
		return fmt.Errorf("incorrect usage: DELETE <key>")
	}
	_, ok := kv[args[0]]
	if !ok {
		return fmt.Errorf("key does not exist")
	}
	delete(kv, args[0])
	return nil
}

// whichDB returns which db is currently being written to
func whichDB(d *DB) map[string]string {
	if d.PKV {
		return d.KV1
	}
	return d.KV2
}