// Expect retcode = 0

// 编译器自身日志（区别于 diag：diag 负责带源码位置的诊断）。
// 输出到 stderr，格式稳定：[LEVEL] name: message\n。
// 消息为借用；Logger 不拥有 name。fatal 打印后终止进程（退出码 1）。
// write 返回 Status；OOM 归类为 .Overflow（无独立内存耗尽错误码）。

type .{ .Status, .make } = @import("error.spl");
type .{ .ByteView } = @import("byte_view.spl");
type .{ .ByteBuffer } = @import("byte_buffer.spl");
type .{ .format } = @import("fmt.spl");
type .{ .Value, .int, .str } = @import("value.spl");
type .{ .eprint } = @import("io.spl");
type Exit = @import("../sys/exit.spl");

type Level = enum { Debug, Info, Warn, Error, Fatal }

fn level_name(level: Level): []u8 {
    match level {
        .Debug => { ret "DEBUG"; },
        .Info => { ret "INFO "; },
        .Warn => { ret "WARN "; },
        .Error => { ret "ERROR"; },
        .Fatal => { ret "FATAL"; },
    }
    ret "NOTSET";
}

type Logger = @self;

name: ByteView,
min_level: Level,

fn new(name: ByteView): Logger {
    ret Logger { .name = name, .min_level = .Debug };
}

fn set_level(self: *Logger, level: Level) {
    self.min_level = level;
}

fn enabled(self: Logger, level: Level): bool {
    ret @enum2int(level) >= @enum2int(self.min_level);
}

// 追加成功返回 true；失败（仅 OOM）返回 false。
fn push(line: *ByteBuffer, text: []u8): bool {
    match ByteBuffer.append(line, text) {
        .Ok => { ret true; },
        .Err(error) => { ret false; },
    }
    ret false;
}

// 低于 min_level 的日志不写出，直接成功。
fn write(self: *Logger, level: Level, message: []u8): Status {
    if !enabled(self.*, level) { ret .Ok; }
    var line = ByteBuffer.new();
    defer { ByteBuffer.drop(&line); }
    if !push(&line, "[") { ret .Err(make(.Overflow)); }
    if !push(&line, level_name(level)) { ret .Err(make(.Overflow)); }
    if !push(&line, "] ") { ret .Err(make(.Overflow)); }
    if !push(&line, ByteView.as_slice(self.name)) { ret .Err(make(.Overflow)); }
    if !push(&line, ": ") { ret .Err(make(.Overflow)); }
    if !push(&line, message) { ret .Err(make(.Overflow)); }
    if !push(&line, "\n") { ret .Err(make(.Overflow)); }
    ret eprint(ByteBuffer.as_slice(line));
}

fn debug(self: *Logger, message: []u8): Status {
    ret write(self, .Debug, message);
}

fn info(self: *Logger, message: []u8): Status {
    ret write(self, .Info, message);
}

fn warn(self: *Logger, message: []u8): Status {
    ret write(self, .Warn, message);
}

fn error(self: *Logger, message: []u8): Status {
    ret write(self, .Error, message);
}

// 尽力写出后终止；写失败无法挽回，直接退出。
fn fatal(self: *Logger, message: []u8) {
    write(self, .Fatal, message);
    Exit.fail();
}

// ---- 格式化入口（显式装箱，见 value.spl / fmt.format）----

// 先格式化到临时缓冲；格式错误在写出前返回 Err(.InvalidFormat)。
fn logf(self: *Logger, level: Level, fmt: []u8, args: []Value): Status {
    if !enabled(self.*, level) { ret .Ok; }
    var message = ByteBuffer.new();
    defer { ByteBuffer.drop(&message); }
    match format(&message, fmt, args) {
        .Ok => {},
        .Err(error) => { ret .Err(error); },
    }
    ret write(self, level, ByteBuffer.as_slice(message));
}

fn debugf(self: *Logger, fmt: []u8, args: []Value): Status {
    ret logf(self, .Debug, fmt, args);
}

fn infof(self: *Logger, fmt: []u8, args: []Value): Status {
    ret logf(self, .Info, fmt, args);
}

fn warnf(self: *Logger, fmt: []u8, args: []Value): Status {
    ret logf(self, .Warn, fmt, args);
}

fn errorf(self: *Logger, fmt: []u8, args: []Value): Status {
    ret logf(self, .Error, fmt, args);
}

// 格式化后终止；格式化失败也要退出（避免吞掉致命错误）。
fn fatalf(self: *Logger, fmt: []u8, args: []Value) {
    logf(self, .Fatal, fmt, args);
    Exit.fail();
}

// ---- 测试 ----

fn expect_name(level: Level, expected: []u8) {
    @assert(ByteView.eq(ByteView.from_slice(level_name(level)),
                        ByteView.from_slice(expected)),
            "level name");
}

fn expect_ok(result: Status) {
    match result {
        .Ok => {},
        .Err(error) => { @assert(false, "unexpected log error"); },
    }
}

fn test_level_names() {
    expect_name(.Debug, "DEBUG");
    expect_name(.Info, "INFO ");
    expect_name(.Warn, "WARN ");
    expect_name(.Error, "ERROR");
    expect_name(.Fatal, "FATAL");

    var debug: Level = .Debug;
    var info: Level = .Info;
    var warn: Level = .Warn;
    var err: Level = .Error;
    var fatal: Level = .Fatal;
    @assert(@enum2int(fatal) > @enum2int(err), "fatal above error");
    @assert(@enum2int(err) > @enum2int(warn), "error above warn");
    @assert(@enum2int(warn) > @enum2int(info), "warn above info");
    @assert(@enum2int(info) > @enum2int(debug), "info above debug");
}

fn test_filter_and_write() {
    var log = new(ByteView.from_slice("splc1"));
    @assert(enabled(log, .Debug), "default shows debug");
    @assert(enabled(log, .Fatal), "default shows fatal");

    set_level(&log, .Warn);
    @assert(!enabled(log, .Debug), "filtered debug");
    @assert(!enabled(log, .Info), "filtered info");
    @assert(enabled(log, .Warn), "warn passes");
    @assert(enabled(log, .Error), "error passes");

    // 被过滤的写入不产生输出，且返回成功。
    expect_ok(debug(&log, "hidden"));
    expect_ok(write(&log, .Info, "hidden too"));
    expect_ok(error(&log, "visible"));
}

fn test_logf() {
    var log = new(ByteView.from_slice("splc1"));
    set_level(&log, .Error);

    var args: [2]Value = .[int(3), str("x")];

    // 被过滤的级别不写出，直接成功。
    expect_ok(infof(&log, "n={} s={}", args[0..2]));
    // 通过级别正常写出。
    expect_ok(errorf(&log, "n={} s={}", args[0..2]));

    // 格式化失败向上传播，且不产出消息。
    match errorf(&log, "{} {}", args[0..1]) {
        .Ok => { @assert(false, "expected invalid format"); },
        .Err(error) => {
            match error.kind {
                .InvalidFormat => {},
                _ => { @assert(false, "expected InvalidFormat"); },
            }
        },
    }
}

fn main() {
    test_level_names();
    test_filter_and_write();
    test_logf();
}