// Phase 0 baseline (PLAN-FFI.md step 0.5): the three shapes that
// actually appear at the sx ↔ C boundary today:
//
//   1. Null-terminated `[:0]u8`  — passed by `.ptr` to a `const char *`.
//   2. Raw byte buffer `[*]u8`   — pointer + explicit length.
//   3. sx `string` value         — coerceArg's "fat-pointer decay" branch
//                                  pulls `.ptr` automatically for `*u8`/
//                                  `[:0]u8` params (string is `{ptr, len}`).
//   4. Pointer return from C     — round-trips back as `[*]u8` / `*u8`.

#import "modules/std.sx";

#import c {
    #source "ffi-05-string-args.c";
};

ffi_strlen          :: (s: [:0]u8)                    -> s32 #foreign;
ffi_first_byte      :: (s: [:0]u8)                    -> s32 #foreign;
ffi_sum_bytes       :: (buf: [*]u8, len: s32)         -> s32 #foreign;
ffi_write_byte      :: (buf: [*]u8, idx: s32, v: u8)  -> void #foreign;
ffi_static_greeting :: ()                             -> [*]u8 #foreign;

main :: () -> s32 {
    // ── [:0]u8 null-terminated literal ─────────────────────────────
    msg : [:0]u8 = "hello";
    print("strlen(\"hello\")     = {}\n", ffi_strlen(msg));
    print("first_byte           = {}\n", ffi_first_byte(msg));

    // ── sx `string` → C `const char *` (slice-decay through coerceArg) ─
    s : string = "sx string here";
    print("strlen(sx string)    = {}\n", ffi_strlen(xx s.ptr));

    // ── [*]u8 raw buffer + length ──────────────────────────────────
    bytes : [4]u8 = .[10, 20, 30, 40];
    bp : [*]u8 = xx @bytes[0];
    print("sum_bytes([10,20,30,40]) = {}\n", ffi_sum_bytes(bp, 4));

    // ── Mutate buffer via C, read back from sx ─────────────────────
    ffi_write_byte(bp, 1, 99);
    print("bytes[1] after write = {}\n", bytes[1]);

    // ── C returns a static string pointer; read it byte-by-byte ────
    g := ffi_static_greeting();
    n := ffi_strlen(xx g);
    print("static greeting len  = {}\n", n);
    print("static greeting [0]  = {}\n", g[0]);

    0;
}
