Redis 事务与 Lua：中途失败后，哪些修改还在

import java.util.*;
public class Main {
    record Command(String op,String key,String value) {}
    record Result(String status,List<String> items) {}
    static class Store {
        final Map<String,String> values=new HashMap<>();
        final Map<String,Long> versions=new HashMap<>();
        long clock;
        void set(String key,String value) {
            clock=Math.addExact(clock,1);
            values.put(key,value); versions.put(key,clock);
        }
        long version(String key) { return versions.getOrDefault(key,0L); }
        Result exec(List<Command> commands,Map<String,Long> watched) {
            for (Command c:commands) {
                // 排队格式错误在任何命令执行之前拒绝。
                if (c.key()==null||!("SET".equals(c.op())||"INCR".equals(c.op()))||
                        ("SET".equals(c.op())&&c.value()==null))
                    return new Result("QUEUE_ERROR",List.of());
            }
            for (var w:watched.entrySet())
                if (version(w.getKey())!=w.getValue())
                    return new Result("WATCH_ABORT",List.of());
            List<String> results=new ArrayList<>();
            for (Command c:commands) {
                if ("SET".equals(c.op())) { set(c.key(),c.value()); results.add("OK"); }
                else {
                    try {
                        long old=Long.parseLong(values.getOrDefault(c.key(),"0"));
                        long next=Math.addExact(old,1);
                        set(c.key(),Long.toString(next)); results.add(Long.toString(next));
                    } catch (NumberFormatException | ArithmeticException error) {
                        results.add("ERR"); // 运行错误不撤销此前写入，也不终止后续命令。
                    }
                }
            }
            return new Result("EXECUTED",List.copyOf(results));
        }
    }
    static Command set(String k,String v) { return new Command("SET",k,v); }
    static Command incr(String k) { return new Command("INCR",k,null); }
    static void eq(Object expected,Object actual) {
        if (!Objects.equals(expected,actual)) throw new AssertionError(actual);
    }
    public static void main(String[] args) {
        Store s=new Store();
        eq(List.of("OK","6"),s.exec(List.of(set("n","5"),incr("n")),Map.of()).items());
        eq(List.of("OK","ERR","OK"),s.exec(List.of(set("n","hello"),incr("n"),set("after","done")),Map.of()).items());
        eq("hello",s.values.get("n")); eq("done",s.values.get("after"));
        eq("QUEUE_ERROR",s.exec(List.of(set("x","1"),new Command("BAD","z",null)),Map.of()).status());
        eq(false,s.values.containsKey("x"));
        Map<String,Long> watch=Map.of("n",s.version("n"));
        s.set("n","changed"); // 模拟WATCH与EXEC之间另一个客户端修改。
        eq("WATCH_ABORT",s.exec(List.of(set("x","1")),watch).status());
        eq(false,s.values.containsKey("x"));
        eq(new Result("EXECUTED",List.of()),s.exec(List.of(),Map.of()));
        System.out.println("PASS 9 Redis transaction assertions");
    }
}