package kvrepl

import (
	"fmt"
	"os"
	"strings"
)

// Parse decides what commands to run and returns a string containing the
// value of a read or an error if one occurred.
func Parse(s string, d *DB) (string, error) {
	args := strings.Split(s, " ")

	switch strings.ToLower(args[0]) {
	case "read":
		return read(args[1:], whichDB(d))
	case "write":
		return "", write(args[1:], whichDB(d))
	case "delete":
		return "", del(args[1:], whichDB(d))
	case "start":
		if len(args) != 1 {
			return "", fmt.Errorf("incorrect usage: START")
		}
		d.nest++
		d.PKV = false

		// copy contents of KV1 to KV2
		d.KV2 = make(map[string]string)
		for k, v := range d.KV1 {
			d.KV2[k] = v
		}
	case "commit":
		if len(args) != 1 {
			return "", fmt.Errorf("incorrect usage: COMMIT")
		}
		if d.PKV {
			return "", fmt.Errorf("not in a transaction")
		}
		if d.nest == 0 {
			d.PKV = true
			// copy contents of KV2 to KV1
			d.KV1 = make(map[string]string)
			for k, v := range d.KV2 {
				d.KV1[k] = v
			}
		}

	case "abort":
		if len(args) != 1 {
			return "", fmt.Errorf("incorrect usage: ABORT")
		}
		d.PKV = true
	case "quit":
		fmt.Println("goodbye")
		os.Exit(0)
	default:
		fmt.Println("not known command")
	}
	return "", nil
}