package buildfile

import (
	"strings"
)

type instruction_type byte

const (
	// INSTALL one or more package(s)
	INSTALL instruction_type = iota
	// UPDATE all installed packages candidates
	UPDATE
	// REMOVE one or more package(s)
	REMOVE
	// SERVICE management (enable, disable, start, stop, restart, reload)
	SERVICE
	// CONF edits configuration files
	CONF
)

// instruction is self-explanatory
type instruction struct {
	Type instruction_type
	// Sub command instruction-type-specific
	Sub  []string
	Args string
}

// createInstruction from a raw line
func createInstruction(raw string) (*instruction, error) {

	// 1. fail if invalid base syntax 'cmd args...'
	// where command is 3 letters
	if len(raw) < 5 || len(strings.Trim(raw[0:3], " ")) < 3 || raw[1] == ' ' || raw[3] != ' ' {
		return nil, ErrInvalidSyntax
	}

	// 2. prepare instruction
	inst := &instruction{
		Type: INSTALL,
		Sub:  make([]string, 0),
		Args: raw[4:],
	}

	// 3. Extract instruction type
	switch raw[0:3] {
	case "ins":
		inst.Type = INSTALL
	case "upd":
		inst.Type = UPDATE
	case "del":
		inst.Type = REMOVE
	case "ser":
		inst.Type = SERVICE
	case "cnf":
		inst.Type = CONF
	default:
		return nil, ErrUnknownInstruction
	}

	return inst, nil
}