package transaction

import "testing"

// TestStateTransitions 验证状态机的正常推进、跳过前向状态、回滚与终态等转换规则。
//
// 覆盖场景：CREATED 到 COMMITTED 的逐级前向推进均被允许；跳过中间状态（CREATED
// 直接到 PREPARED）被拒绝；SWITCHING 允许进入回滚、ROLLING_BACK 允许到 ROLLED_BACK；
// 终态 COMMITTED 不再接受任何后续转换。
func TestStateTransitions(t *testing.T) {
	t.Parallel()
	forward := []State{
		StateCreated,
		StateValidating,
		StatePrepared,
		StateStarting,
		StateSwitching,
		StateVerifying,
		StateDraining,
		StateCommitted,
	}
	for index := 0; index < len(forward)-1; index++ {
		if !forward[index].CanTransitionTo(forward[index+1]) {
			t.Fatalf("expected transition %s -> %s", forward[index], forward[index+1])
		}
	}
	if StateCreated.CanTransitionTo(StatePrepared) {
		t.Fatal("state machine accepted a skipped forward state")
	}
	if !StateSwitching.CanTransitionTo(StateRollingBack) {
		t.Fatal("state machine rejected rollback")
	}
	if !StateRollingBack.CanTransitionTo(StateRolledBack) {
		t.Fatal("state machine rejected rollback completion")
	}
	if StateCommitted.CanTransitionTo(StateRollingBack) {
		t.Fatal("terminal state accepted another transition")
	}
}