# emit_os.ludic — the Os.* namespace: the environment *around* the game — the
# command line, environment variables, standard streams, process exit, the host
# platform, and the per-user known folders a game writes into. Go-flavored and
# game-scoped: no process spawning, signals, or permission APIs — just the facts
# a launcher, an asset pipeline, or a save system needs.
#
#   Os.args()              -> []string   every command-line argument (argv[0..])
#   Os.arg_count()         -> int        how many arguments there are
#   Os.arg(i)              -> string     the i-th argument (0 = the program path)
#   Os.env(name)           -> string     an environment variable, or null if unset
#   Os.env_or(name, fb)    -> string     ...or `fb` when it is unset/empty-null
#   Os.has_env(name)       -> bool       is the variable set?
#   Os.set_env(name, val)  -> bool       set it (true on success)
#   Os.unset_env(name)     -> bool       remove it (true on success)
#   Os.exit(code)                        terminate the process with a status code
#   Os.pid()               -> int        this process's id (unique among live processes)
#   Os.platform()          -> string     "macos" | "linux" | ...(raw uname sysname)
#   Os.arch()              -> string     machine arch, e.g. "arm64" | "x86_64"
#   Os.stdout_write(s)                   write a string to standard output
#   Os.stderr_write(s)                   write a string to standard error
#   Os.save_dir(app)       -> string     per-user save directory for `app`
#   Os.config_dir(app)     -> string     per-user config directory for `app`
#   Os.cache_dir(app)      -> string     per-user cache directory for `app`
#   Os.temp_dir()          -> string     the system temporary directory
#   Os.heap_bytes()        -> long       malloc's live bytes (macOS; 0 elsewhere): a test that a
#                                        path allocates nothing, with no renderer linked in
#   Os.heap_relief()       -> long       give the heap's freed-but-cached memory back to the system
#                                        (macOS malloc_zone_pressure_relief, Windows HeapCompact;
#                                        0 elsewhere): once after a load, never per frame
#
# Determinism: args/env/platform are non-deterministic host input — read them at
# startup to configure the game, but keep them out of the replayable simulation.
#
# Platform coverage: this v1 targets the native (macOS/BSD) host, the only fully
# supported target today. platform() is portable (uname sysname is field 0 on
# every Unix); arch() and the known-folder layout assume the macOS/BSD utsname
# and directory conventions. Linux/Windows/wasm known-folder resolution and a
# target-aware arch() are documented follow-ups (see issue #21).

function is_os_ns(meth: pointer) -> bool {
  if (meth == "args") or (meth == "arg_count") or (meth == "arg") { return true }
  if (meth == "env") or (meth == "env_or") or (meth == "has_env") { return true }
  if (meth == "set_env") or (meth == "unset_env") { return true }
  if (meth == "exit") or (meth == "pid") or (meth == "platform") or (meth == "arch") { return true }
  if (meth == "stdout_write") or (meth == "stderr_write") { return true }
  if (meth == "save_dir") or (meth == "config_dir") or (meth == "cache_dir") or (meth == "temp_dir") { return true }
  if (meth == "heap_bytes") or (meth == "heap_relief") { return true }
  return false
}

function emit_os_ns(meth: pointer, e: Node) -> Val {
  # arg_count / arg / exit / pid stay light — they mirror the bare intrinsics and
  # need no Os runtime prelude, so a program using only these emits no extra IR.
  if (meth == "arg_count") { return val(emit_bind("load i32, ptr @L_argc"), "int") }
  if (meth == "arg") {
    let i = emit_expr(e.kids[0])
    let v = emit_bind("load ptr, ptr @L_argv")
    let q = emit_bind(`getelementptr ptr, ptr {v}, i32 {i.code}`)
    return val(emit_bind(`load ptr, ptr {q}`), "string")
  }
  if (meth == "pid") { g_uses_pid = true;  return val(emit_bind("call i32 @getpid()"), "int") }
  if (meth == "heap_bytes") {
    if g_target_win { return val("0", "long") }
    g_uses_heap = true
    return val(emit_bind("call i64 @lp_os_heap_bytes()"), "long")
  }
  if (meth == "heap_relief") {
    g_uses_relief = true
    return val(emit_bind("call i64 @lp_os_heap_relief()"), "long")
  }
  if (meth == "exit") {
    let n = emit_expr(e.kids[0])
    emit(`  call void @exit(i32 {n.code})\n`)
    emit("  unreachable\n")
    g_term = true
    return val("0", "void")
  }
  if (meth == "env") {                              # raw getenv: null when unset
    let nm = emit_expr(e.kids[0])
    return val(emit_bind(`call ptr @getenv(ptr {nm.code})`), "string")
  }
  if (meth == "has_env") {
    let nm = emit_expr(e.kids[0])
    let r = emit_bind(`call ptr @getenv(ptr {nm.code})`)
    let ne = emit_bind(`icmp ne ptr {r}, null`)
    return val(emit_bind(`zext i1 {ne} to i32`), "bool")
  }
  if (meth == "stdout_write") or (meth == "stderr_write") {
    var fd = 1
    if (meth == "stderr_write") { fd = 2 }
    let s = emit_expr(e.kids[0])
    let f = emit_bind(stdstream_rhs(fd))
    let n = emit_bind(`call i64 @strlen(ptr {s.code})`)
    emit(`  call i64 @fwrite(ptr {s.code}, i64 1, i64 {n}, ptr {f})\n`)
    return val("0", "void")
  }
  # everything below is served by the Os runtime prelude
  g_uses_osrt = true
  if (meth == "args") { return val(emit_bind("call ptr @lp_os_args()"), "[]string") }
  if (meth == "env_or") {
    let nm = emit_expr(e.kids[0]);  let fb = emit_expr(e.kids[1])
    return val(emit_bind(`call ptr @lp_os_getenv_or(ptr {nm.code}, ptr {fb.code})`), "string")
  }
  if (meth == "set_env") {
    let nm = emit_expr(e.kids[0]);  let v = emit_expr(e.kids[1])
    let r = emit_bind(`call i32 @setenv(ptr {nm.code}, ptr {v.code}, i32 1)`)
    let ok = emit_bind(`icmp eq i32 {r}, 0`)
    return val(emit_bind(`zext i1 {ok} to i32`), "bool")
  }
  if (meth == "unset_env") {
    let nm = emit_expr(e.kids[0])
    let r = emit_bind(`call i32 @unsetenv(ptr {nm.code})`)
    let ok = emit_bind(`icmp eq i32 {r}, 0`)
    return val(emit_bind(`zext i1 {ok} to i32`), "bool")
  }
  if (meth == "platform") { return val(emit_bind("call ptr @lp_os_platform()"), "string") }
  if (meth == "arch")     { return val(emit_bind("call ptr @lp_os_arch()"), "string") }
  if (meth == "save_dir") {
    let a = emit_expr(e.kids[0])
    return fresh_val(emit_bind(`call ptr @lp_os_save_dir(ptr {a.code})`), "string")
  }
  if (meth == "config_dir") {
    let a = emit_expr(e.kids[0])
    return fresh_val(emit_bind(`call ptr @lp_os_config_dir(ptr {a.code})`), "string")
  }
  if (meth == "cache_dir") {
    let a = emit_expr(e.kids[0])
    return fresh_val(emit_bind(`call ptr @lp_os_cache_dir(ptr {a.code})`), "string")
  }
  # temp_dir: the environment's own text on POSIX, a copy of its own on Windows
  if g_target_win { return fresh_val(emit_bind("call ptr @lp_os_temp_dir()"), "string") }
  return val(emit_bind("call ptr @lp_os_temp_dir()"), "string")
}

# emit_os_prelude — the Os runtime, emitted once per program that uses the
# prelude-backed Os.* methods (g_uses_osrt). Pure libc over NUL-terminated
# strings; declares the few POSIX symbols the header does not already carry.
function emit_os_prelude() -> void {
  if not g_target_win {                        # defined by emit_win_prelude on Windows
    emith("declare i32 @setenv(ptr, ptr, i32)\n")
    emith("declare i32 @unsetenv(ptr)\n")
    emith("declare i32 @uname(ptr)\n")
  }

  # string constants (escaped + length-counted by emit_str_const)
  let k_home  = emit_str_const("HOME")
  let k_dot   = emit_str_const(".")
  let k_appsp = emit_str_const("/Library/Application Support/")
  let k_cache = emit_str_const("/Library/Caches/")
  let k_tmpk  = emit_str_const("TMPDIR")
  let k_tmp   = emit_str_const("/tmp")
  let k_darw  = emit_str_const("Darwin")
  # XDG (Linux): the variable, and the fallback the spec names for it
  let k_xdg_data   = emit_str_const("XDG_DATA_HOME")
  let k_xdg_cfg    = emit_str_const("XDG_CONFIG_HOME")
  let k_xdg_cache  = emit_str_const("XDG_CACHE_HOME")
  let k_dot_share  = emit_str_const("/.local/share/")
  let k_dot_config = emit_str_const("/.config/")
  let k_dot_cache  = emit_str_const("/.cache/")
  let k_slash      = emit_str_const("/")
  let k_macos = emit_str_const("macos")
  let k_linux_k = emit_str_const("Linux")
  let k_linux   = emit_str_const("linux")

  # getenv(name) or a fallback when it is unset
  emith("define ptr @lp_os_getenv_or(ptr %name, ptr %fb) {\n")
  emith("entry:\n  %r = call ptr @getenv(ptr %name)\n  %z = icmp eq ptr %r, null\n  br i1 %z, label %use, label %got\n")
  emith("use:\n  ret ptr %fb\n")
  emith("got:\n  ret ptr %r\n}\n")

  # concatenate two NUL-terminated strings into a fresh malloc'd buffer
  emith("define ptr @lp_os_join2(ptr %a, ptr %b) {\n")
  emith("entry:\n  %la = call i64 @strlen(ptr %a)\n  %lb = call i64 @strlen(ptr %b)\n")
  emith("  %sum = add i64 %la, %lb\n  %tot = add i64 %sum, 1\n  %m = call ptr @lp_malloc(i64 %tot)\n")
  emith("  call ptr @memcpy(ptr %m, ptr %a, i64 %la)\n")
  emith("  %m2 = getelementptr i8, ptr %m, i64 %la\n  call ptr @memcpy(ptr %m2, ptr %b, i64 %lb)\n")
  emith("  %end = getelementptr i8, ptr %m, i64 %sum\n  store i8 0, ptr %end\n  ret ptr %m\n}\n")

  emith("define ptr @lp_os_join3(ptr %a, ptr %b, ptr %c) {\n")
  emith("entry:\n  %ab = call ptr @lp_os_join2(ptr %a, ptr %b)\n  %r = call ptr @lp_os_join2(ptr %ab, ptr %c)\n  call void @lp_free(ptr %ab)\n  ret ptr %r\n}\n")

  # Windows has its own known folders and no uname; emit_win.ludic supplies them
  if g_target_win { emit_os_win_known(k_dot, k_slash);  return }

  # the user's home directory, or "." when HOME is unset
  emith(`define ptr @lp_os_home() {{\n  %r = call ptr @lp_os_getenv_or(ptr {k_home}, ptr {k_dot})\n  ret ptr %r\n}}\n`)

  # ---- per-user known folders ------------------------------------------------
  #
  # These used to be the macOS layout on every platform, so a game built on Linux
  # wrote its saves to ~/Library/Application Support - a path that means nothing
  # there. The directory a platform keeps save games in is not a detail a game
  # should have to know, which is the whole reason these functions exist.
  #
  #   macOS   save/config  ~/Library/Application Support/<app>
  #           cache        ~/Library/Caches/<app>
  #   Linux   save         $XDG_DATA_HOME   or ~/.local/share/<app>
  #           config       $XDG_CONFIG_HOME or ~/.config/<app>
  #           cache        $XDG_CACHE_HOME  or ~/.cache/<app>
  #
  # macOS keeps save_dir and config_dir the same path, as it always has: Apple's
  # place for a config file that is not an NSUserDefaults plist is Application
  # Support too, and a game that shipped on the old behaviour must not have its
  # settings moved out from under it. On Linux XDG separates the two and so do we.
  #
  # An XDG variable that is set but EMPTY falls back to the default, which is what
  # the spec says and what a shell that exports an unset variable produces.

  # is this macOS? uname once, then remembered - save_dir is called per save.
  emith("@L_os_darwin = internal global i32 -1\n")
  emith("define i32 @lp_os_is_darwin() {\n")
  emith("entry:\n  %c = load i32, ptr @L_os_darwin\n  %known = icmp sge i32 %c, 0\n  br i1 %known, label %done, label %probe\n")
  emith("done:\n  ret i32 %c\n")
  emith("probe:\n  %buf = call ptr @lp_malloc(i64 8192)\n  call i32 @uname(ptr %buf)\n")
  emith(`  %cd = call i32 @strncmp(ptr %buf, ptr {k_darw}, i64 6)\n  %isd = icmp eq i32 %cd, 0\n`)
  emith("  %r = select i1 %isd, i32 1, i32 0\n  call void @lp_free(ptr %buf)\n  store i32 %r, ptr @L_os_darwin\n  ret i32 %r\n}\n")

  # $<var> when it is set and non-empty, else $HOME<rel>; the result always ends in '/'
  emith("define ptr @lp_os_xdg(ptr %var, ptr %rel) {\n")
  emith("entry:\n  %v = call ptr @getenv(ptr %var)\n  %z = icmp eq ptr %v, null\n  br i1 %z, label %dflt, label %chk\n")
  emith("chk:\n  %c0 = load i8, ptr %v\n  %empty = icmp eq i8 %c0, 0\n  br i1 %empty, label %dflt, label %use\n")
  emith(`use:\n  %u = call ptr @lp_os_join2(ptr %v, ptr {k_slash})\n  ret ptr %u\n`)
  emith("dflt:\n  %h = call ptr @lp_os_home()\n  %d = call ptr @lp_os_join2(ptr %h, ptr %rel)\n  ret ptr %d\n}\n")

  # one known folder: the macOS path, or the XDG one
  emith("define ptr @lp_os_known(ptr %app, ptr %mac, ptr %var, ptr %rel) {\n")
  emith("entry:\n  %d = call i32 @lp_os_is_darwin()\n  %isd = icmp ne i32 %d, 0\n  br i1 %isd, label %m, label %x\n")
  emith("m:\n  %h = call ptr @lp_os_home()\n  %r1 = call ptr @lp_os_join3(ptr %h, ptr %mac, ptr %app)\n  ret ptr %r1\n")
  emith("x:\n  %b = call ptr @lp_os_xdg(ptr %var, ptr %rel)\n  %r2 = call ptr @lp_os_join2(ptr %b, ptr %app)\n  call void @lp_free(ptr %b)\n  ret ptr %r2\n}\n")

  emith(`define ptr @lp_os_save_dir(ptr %app) {{\n  %r = call ptr @lp_os_known(ptr %app, ptr {k_appsp}, ptr {k_xdg_data}, ptr {k_dot_share})\n  ret ptr %r\n}}\n`)
  emith(`define ptr @lp_os_config_dir(ptr %app) {{\n  %r = call ptr @lp_os_known(ptr %app, ptr {k_appsp}, ptr {k_xdg_cfg}, ptr {k_dot_config})\n  ret ptr %r\n}}\n`)
  emith(`define ptr @lp_os_cache_dir(ptr %app) {{\n  %r = call ptr @lp_os_known(ptr %app, ptr {k_cache}, ptr {k_xdg_cache}, ptr {k_dot_cache})\n  ret ptr %r\n}}\n`)
  emith(`define ptr @lp_os_temp_dir() {{\n  %r = call ptr @lp_os_getenv_or(ptr {k_tmpk}, ptr {k_tmp})\n  ret ptr %r\n}}\n`)

  # Os.args() -> a %LSlice of the argv strings (data = argv, len = cap = argc), a
  # snapshot the caller may iterate or index like any other []string.
  emith("define ptr @lp_os_args() {\n")
  emith("entry:\n  %c = load i32, ptr @L_argc\n  %v = load ptr, ptr @L_argv\n")
  emith("  %h = call ptr @lp_malloc(i64 16)\n")
  emith("  %d0 = getelementptr inbounds %LSlice, ptr %h, i32 0, i32 0\n  store ptr %v, ptr %d0\n")
  emith("  %d1 = getelementptr inbounds %LSlice, ptr %h, i32 0, i32 1\n  store i32 %c, ptr %d1\n")
  emith("  %d2 = getelementptr inbounds %LSlice, ptr %h, i32 0, i32 2\n  store i32 %c, ptr %d2\n")
  emith("  ret ptr %h\n}\n")

  # uname once, into a buffer kept for the program's life: platform() and arch() are asked every
  # frame by some callers, and each call once malloc'd 8 KB for it and let it go
  emith("@L_os_uts = internal global ptr null\n")
  emith("define ptr @lp_os_uts() {\n")
  emith("entry:\n  %c = load ptr, ptr @L_os_uts\n  %have = icmp ne ptr %c, null\n  br i1 %have, label %done, label %make\n")
  emith("done:\n  ret ptr %c\n")
  emith("make:\n  %buf = call ptr @lp_malloc(i64 8192)\n  call i32 @uname(ptr %buf)\n  store ptr %buf, ptr @L_os_uts\n  ret ptr %buf\n}\n")

  # platform(): uname sysname (field 0, portable) mapped to a short id
  emith("define ptr @lp_os_platform() {\n")
  emith("entry:\n  %buf = call ptr @lp_os_uts()\n")
  emith(`  %cd = call i32 @strncmp(ptr %buf, ptr {k_darw}, i64 6)\n  %isd = icmp eq i32 %cd, 0\n  br i1 %isd, label %mac, label %chkl\n`)
  emith(`mac:\n  ret ptr {k_macos}\n`)
  emith(`chkl:\n  %cl = call i32 @strncmp(ptr %buf, ptr {k_linux_k}, i64 5)\n  %isl = icmp eq i32 %cl, 0\n  br i1 %isl, label %lin, label %other\n`)
  emith(`lin:\n  ret ptr {k_linux}\n`)
  emith("other:\n  ret ptr %buf\n}\n")

  # arch(): the uname `machine` field. On macOS/BSD utsname each field is 256
  # bytes, so `machine` (index 4) sits at offset 1024. Documented BSD-layout
  # assumption (see the header note); other layouts are a follow-up.
  emith("define ptr @lp_os_arch() {\n")
  emith("entry:\n  %buf = call ptr @lp_os_uts()\n")
  emith("  %m = getelementptr i8, ptr %buf, i64 1024\n  ret ptr %m\n}\n")
}

# Os.heap_relief: what the allocator keeps cached after a free (a large block libmalloc holds EMPTY)
# handed back, the bytes it says it released. Weak outside Windows, so a libc without it reads 0
function emit_os_relief() -> void {
  emith("define i64 @lp_os_heap_relief() {\nentry:\n")
  if g_target_win {
    emith("  %h = call ptr @GetProcessHeap()\n  %n = call i64 @HeapCompact(ptr %h, i32 0)\n  ret i64 %n\n}\n")
    emith("declare ptr @GetProcessHeap()\ndeclare i64 @HeapCompact(ptr, i32)\n")
    return
  }
  emith("  %mz = icmp ne ptr @malloc_zone_pressure_relief, null\n  br i1 %mz, label %mac, label %none\n")
  emith("mac:\n  %n = call i64 @malloc_zone_pressure_relief(ptr null, i64 0)\n  ret i64 %n\n")
  emith("none:\n  ret i64 0\n}\n")
  emith("declare extern_weak i64 @malloc_zone_pressure_relief(ptr, i64)\n")
}

# Os.heap_bytes: malloc_zone_statistics' in-use bytes, all zones. The symbol is weak, so a libc
# without it links and reads 0.
function emit_os_heap() -> void {
  if not g_mzs_declared { emith("declare extern_weak void @malloc_zone_statistics(ptr, ptr)\n");  g_mzs_declared = true }
  emith("define i64 @lp_os_heap_bytes() {\n")
  emith("entry:\n  %has = icmp ne ptr @malloc_zone_statistics, null\n  br i1 %has, label %read, label %none\n")
  emith("none:\n  ret i64 0\n")
  emith("read:\n  %st = alloca [4 x i64], align 8\n  call void @malloc_zone_statistics(ptr null, ptr %st)\n")
  emith("  %p = getelementptr [4 x i64], ptr %st, i32 0, i32 1\n  %n = load i64, ptr %p\n  ret i64 %n\n}\n")
}