// Expect retcode = 0
// I/O 便利层（构建在 sys/file 之上）：
//   - C 字符串路径/模式的 open 包装
//   - 整块读写（write_all / read_all）
//   - stdout/stderr 打印
// 说明：read_all 会按文件大小一次性读入 ByteBuffer；不处理增长中的文件。

type .{ .Error, .Status, .make } = @import("error.spl");
type .{ .ByteView } = @import("byte_view.spl");
type .{ .ByteBuffer } = @import("byte_buffer.spl");
type File = @import("../sys/file.spl");

// 把 view 复制到以 NUL 结尾的临时缓冲，返回其 data（归属 tmp，调用后勿再用）。
fn cstr(tmp: *ByteBuffer, view: ByteView): *u8 {
    ByteBuffer.clear(tmp);
    if view.len != 0 {
        match ByteBuffer.append(tmp, ByteView.as_slice(view)) {
            .Ok => {},
            .Err(error) => { ret null; },
        }
    }
    match ByteBuffer.append_byte(tmp, '\0') {
        .Ok => {},
        .Err(error) => { ret null; },
    }
    ret tmp.storage.data;
}

fn open_cstr(path: ByteView, mode: ByteView): File {
    var pbuf = ByteBuffer.new();
    var mbuf = ByteBuffer.new();
    var p = cstr(&pbuf, path);
    var m = cstr(&mbuf, mode);
    var f = File.open(p, m);
    ByteBuffer.drop(&pbuf);
    ByteBuffer.drop(&mbuf);
    ret f;
}

// 反复写入直到写完；返回实际写入字节数（!= bytes.len 表示中途失败）。
fn write_all(f: *File, bytes: []u8): u64 {
    var total: u64 = 0;
    var want = bytes.len as u64;
    while total < want {
        var offset = total as usize;
        var w = File.write(f, bytes.ptr + offset, want - total);
        if w == 0 { break; }
        total = total + w;
    }
    ret total;
}

fn print(bytes: []u8) {
    var out = File.stdout();
    write_all(&out, bytes);
}

fn println(bytes: []u8) {
    print(bytes);
    print("\n");
}

fn eprint(bytes: []u8) {
    var err = File.stderr();
    write_all(&err, bytes);
}

// 读取整个文件到 out（先清空）。打开失败或不完整返回 Err(.Io)。
fn read_all(path: ByteView, out: *ByteBuffer): Status {
    var f = open_cstr(path, ByteView.from_slice("rb"));
    if !File.valid(&f) { ret .Err(make(.Io)); }

    var sz = File.size(&f);
    ByteBuffer.clear(out);
    if sz != 0 {
        match ByteBuffer.reserve(out, sz as usize) {
            .Ok => {},
            .Err(error) => { File.close(&f); ret .Err(error); },
        }
        var got = File.read(&f, out.storage.data, sz);
        out.storage.len = got as usize;
        File.close(&f);
        if got != sz { ret .Err(make(.Io)); }
        ret .Ok;
    }
    File.close(&f);
    ret .Ok;
}

// ---- 测试辅助 ----

fn view(text: []u8): ByteView {
    ret ByteView.from_slice(text);
}

fn test_roundtrip() {
    var path = view("build/_io_roundtrip.tmp");

    var f = open_cstr(path, view("wb"));
    @assert(File.valid(&f), "open wb");
    var w = write_all(&f, "hello\nworld");
    @assert(w == 11, "write_all length");
    File.close(&f);

    var out = ByteBuffer.new();
    match read_all(path, &out) {
        .Ok => {},
        .Err(error) => { @assert(false, "read_all"); },
    }
    var got = ByteBuffer.as_slice(out);
    @assert(got.len == 11, "roundtrip length");
    @assert(got.ptr[0] == 'h' && got.ptr[5] == '\n' && got.ptr[10] == 'd', "roundtrip bytes");
    ByteBuffer.drop(&out);
}

fn test_append_and_missing() {
    var path = view("build/_io_append.tmp");

    var f = open_cstr(path, view("wb"));
    @assert(File.valid(&f), "open wb");
    write_all(&f, "ab");
    File.close(&f);

    f = open_cstr(path, view("ab"));
    @assert(File.valid(&f), "open ab");
    var w2 = write_all(&f, "cd");
    File.close(&f);
    @assert(w2 == 2, "append length");

    var out = ByteBuffer.new();
    match read_all(path, &out) {
        .Ok => {},
        .Err(error) => { @assert(false, "read append"); },
    }
    var got = ByteBuffer.as_slice(out);
    @assert(got.len == 4 && got.ptr[2] == 'c' && got.ptr[3] == 'd', "append content");

    // 不存在的文件
    match read_all(view("build/_io_no_such_file.tmp"), &out) {
        .Ok => { @assert(false, "missing should fail"); },
        .Err(error) => {
            match error.kind { .Io => {}, _ => { @assert(false, "error kind"); } }
        },
    }
    ByteBuffer.drop(&out);
}

fn main() {
    test_roundtrip();
    test_append_and_missing();
    println("io: ok");
}