// Expect retcode = 0
// 拥有型字节字符串：在 ByteBuffer 之上提供字符串常用操作。
// 普通赋值复制句柄（共享存储），所有权转移用 take；失败不产生部分状态。

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

type Str = @self;

storage: ByteBuffer,

type StrResult = enum {
    Ok: Str,
    Err: Error,
}

fn new(): Str {
    ret Str { .storage = ByteBuffer.new() };
}

// 复制 view 指向的字节。
fn from_view(view: ByteView): StrResult {
    var s = new();
    match append_view(&s, view) {
        .Ok => {},
        .Err(error) => { drop(&s); ret .Err(error); },
    }
    ret .Ok(s);
}

fn from_slice(bytes: []u8): StrResult {
    ret from_view(ByteView.from_slice(bytes));
}

fn size(self: Str): usize {
    ret ByteBuffer.size(self.storage);
}

fn is_empty(self: Str): bool {
    ret ByteBuffer.is_empty(self.storage);
}

fn as_view(self: *Str): ByteView {
    ret ByteView.from_slice(ByteBuffer.as_slice(self.storage));
}

fn as_slice(self: *Str): []u8 {
    ret ByteBuffer.as_slice(self.storage);
}

fn reserve(self: *Str, capacity: usize): Status {
    ret ByteBuffer.reserve(&self.storage, capacity);
}

fn append_view(self: *Str, view: ByteView): Status {
    ret ByteBuffer.append(&self.storage, ByteView.as_slice(view));
}

fn append(self: *Str, bytes: []u8): Status {
    ret ByteBuffer.append(&self.storage, bytes);
}

fn append_str(self: *Str, other: Str): Status {
    var o = other;
    ret append_view(self, as_view(&o));
}

fn append_byte(self: *Str, byte: u8): Status {
    ret ByteBuffer.append_byte(&self.storage, byte);
}

fn clear(self: *Str) {
    ByteBuffer.clear(&self.storage);
}

fn eq(a: Str, b: Str): bool {
    var x = a;
    var y = b;
    ret ByteView.eq(as_view(&x), as_view(&y));
}

fn eq_slice(a: Str, bytes: []u8): bool {
    var x = a;
    ret ByteView.eq(as_view(&x), ByteView.from_slice(bytes));
}

fn cmp(a: Str, b: Str): i32 {
    var x = a;
    var y = b;
    ret ByteView.cmp(as_view(&x), as_view(&y));
}

fn starts_with(self: Str, prefix: Str): bool {
    var x = self;
    var p = prefix;
    ret ByteView.starts_with(as_view(&x), as_view(&p));
}

fn ends_with(self: Str, suffix: Str): bool {
    var x = self;
    var s = suffix;
    ret ByteView.ends_with(as_view(&x), as_view(&s));
}

fn find(self: Str, needle: Str): FindResult {
    var x = self;
    var n = needle;
    ret ByteView.find(as_view(&x), as_view(&n));
}

// 深复制；允许 out 与 source 为同一对象。
fn clone(out: *Str, source: Str): Status {
    ret ByteBuffer.clone(&out.storage, source.storage);
}

fn take(source: *Str): Str {
    ret Str { .storage = ByteBuffer.take(&source.storage) };
}

fn drop(self: *Str) {
    ByteBuffer.drop(&self.storage);
}

// ---- 测试辅助 ----

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

fn expect_text(s: *Str, expected: []u8) {
    var view = as_view(s);
    @assert(ByteView.eq(view, ByteView.from_slice(expected)), "str text");
}

fn test_construction() {
    var s = new();
    @assert(is_empty(s) && size(s) == 0, "empty new");
    expect_ok(append(&s, "hello"));
    expect_ok(append_byte(&s, ' '));
    expect_ok(append(&s, "world"));
    expect_text(&s, "hello world");
    @assert(size(s) == 11, "size");

    var r = from_slice("copy");
    match r {
        .Ok(copy) => {
            expect_text(&copy, "copy");
            @assert(eq(copy, copy), "self eq");
            drop(&copy);
        },
        .Err(error) => { @assert(false, "from_slice"); },
    }
    drop(&s);
}

fn test_compare_and_search() {
    var hello_r = from_slice("hello");
    var hello: Str = new();
    match hello_r {
        .Ok(v) => { hello = v; },
        .Err(error) => { @assert(false, "hello"); },
    }
    var help_r = from_slice("help");
    var help: Str = new();
    match help_r {
        .Ok(v) => { help = v; },
        .Err(error) => { @assert(false, "help"); },
    }

    @assert(eq(hello, hello), "eq");
    @assert(!eq(hello, help), "ne");
    @assert(eq_slice(hello, "hello"), "eq_slice");
    @assert(cmp(hello, help) < 0, "cmp lt");
    @assert(cmp(help, hello) > 0, "cmp gt");

    @assert(starts_with(hello, hello), "starts_with");
    @assert(ends_with(hello, hello), "ends_with");
    var pre_r = from_slice("he");
    var pre: Str = new();
    match pre_r { .Ok(v) => { pre = v; }, .Err(e) => { @assert(false, "pre"); } }
    @assert(starts_with(hello, pre), "starts he");
    @assert(!ends_with(hello, pre), "!ends he");

    var needle_r = from_slice("ll");
    var needle: Str = new();
    match needle_r { .Ok(v) => { needle = v; }, .Err(e) => { @assert(false, "needle"); } }
    match find(hello, needle) {
        .Found(index) => { @assert(index == 2, "find ll"); },
        .NotFound => { @assert(false, "ll not found"); },
    }
    match find(hello, pre) {
        .Found(index) => { @assert(index == 0, "find he"); },
        .NotFound => { @assert(false, "he not found"); },
    }

    drop(&needle);
    drop(&pre);
    drop(&help);
    drop(&hello);
}

fn test_clone_take_and_failures() {
    var source = new();
    expect_ok(append(&source, "owned"));

    var copy = new();
    expect_ok(clone(&copy, source));
    expect_text(&copy, "owned");
    expect_ok(append_byte(&source, '!')); // '!'
    expect_text(&copy, "owned");         // 独立

    var before = ByteBuffer.as_slice(copy.storage).ptr;
    expect_ok(clone(&copy, copy));
    @assert(ByteBuffer.as_slice(copy.storage).ptr != before, "self clone replaces allocation");
    expect_text(&copy, "owned");

    var moved = take(&copy);
    @assert(ByteBuffer.size(copy.storage) == 0 && ByteBuffer.capacity(copy.storage) == 0,
            "take empties source");
    expect_text(&moved, "owned");

    clear(&moved);
    @assert(is_empty(moved) && ByteBuffer.capacity(moved.storage) != 0, "clear keeps capacity");

    drop(&moved);
    drop(&copy);
    drop(&source);
}

fn main() {
    test_construction();
    test_compare_and_search();
    test_clone_take_and_failures();
}