// vstream — Hare-shaped vtable wrappers over the logger surface.
// Project #94 fold-e5 (Option C, parallel API for lib/log). Last
// per-caller migration before fold-eFinal (task #50).
//
// Adds the ten _v variants of OLD log.ww's surface — new_v /
// lprintln_v / println_v / lprintfln_v / printfln_v / lfatal_v /
// fatal_v / lfatalf_v / fatalf_v / setlogger_v — alongside a vlogger
// vtable + vstdlogger over an io.vstream sink. The OLD surface stays
// untouched here — fold-eFinal (task #50) atomically flips the
// package shape: deletes the OLD logger / stdlogger / globals + the
// pre-vtable stderrsink + ensureinit, renames the `_v` suffix off
// (drops to bare `new` / `println` / etc. per Hare's
// ref/hare/log/{logger,funcs,global,silent}.ha), and migrates the
// few callers (lib/log/logtest.ww plus any downstream).
//
// drew acks (3/3):
//   - module-static stderrsink_ctx (zero-init per #129 A.2/A.3 SSoT)
//   - vt FIRST field intrusive cast (matches fmt/memio/bufio fold-e
//     ctxs)
//   - all 10 OLD fns get _v variants (Option-C consistency)
//
// ken mandates honored:
//   - bootstrap byte-id mechanical pre==post: log is NOT embedded
//     in any selfhost/cmd/*/main.combined.ww (grep-confirmed
//     pre-impl), so adding vstream.ww + minimal export bumps in
//     lib/fmt does not perturb the embedded surfaces. 990-997
//     gates stay green by virtue of log being test-only.
//   - module-static ctx via #129 A.2/A.3 (cs == ww symmetric)
//   - ctx shape simple scalars/ptrs (vt is the established intrusive
//     first-field idiom; the only other field is `fd: i32`. No f32
//     per #165b; no nested aggregate beyond vt per #18).
//
// Hare reference: ref/hare/log/{logger.ha,funcs.ha,global.ha,silent.ha}
// + ref/hare/log/log.ha (re-export hub).
//
// Cast workaround per #206: bare `&fn_name` does not type-check as
// a `(*<alias> | void)` field-init / let-binding. Explicit
// `(&fn_name): *io.<role>` cast at each store site is the Hare-
// faithful minimum-touch route — same workaround memio/vstream.ww
// + fmt/vstream.ww + bufio/vstream.ww use. 2 cast tokens here at
// the stderrsink_ctx_g vt wire-up (reader + writer; no closer —
// the process owns fd 2, same divergence as OLD stderrclose at
// log.ww:162). Both casts drop out wholesale once #206 closes.
//
// Chained-N_DOT-on-module-static field-assign per OLD log.ww:134-140
// (`_default.logger.println = stdprintln;`) — proven-working spine.
// stderrsink_ctx_g.vt.X writes pattern through same shape; the
// tagged-union assign with widening cast composes via #199 α
// (concrete *fn → NAMED variant of (*reader | void) parent).
//
// Newline emission: vfprint / vfprintf are bare (no trailing \n);
// Hare's ref/hare/fmt/wrappers.ha:60-68 appends the newline at the
// fprintln site (after fprint). ww mirrors: stdprintln_v / stdprintfln_v
// call fmt.vfprint / fmt.vfprintf then io.st_write a one-byte slice
// `[10u8]` for the LF. Same shape OLD log.stdprintln uses via
// fmt.fprintln (log.ww:169).
//
// Sibling tasks parked here (filed, NOT fixed):
//
//   - eFinal (#50): atomic flip + delete OLD log surface + drop the
//     `_v` suffix wholesale (graduates to Hare's bare names).
//
//   - #206 (bare &fn → (*alias|void)): 2 cast sites at ensureinit_v;
//     drop out wholesale on close.
//
//   - #173 (TRY-on-tagged-return both-stages broken): stderrwrite_v
//     constructs nomem and widens to io.error explicitly rather than
//     using `os.trywrite(...)?`; same shape memio.vstream.ww +
//     fmt.vstream.ww + bufio.vstream.ww adopt.
//
//   - #207 (struct-lit multi-tagged-field copy drops past first):
//     not bitten here — module-static stderrsink_ctx_g is zero-init
//     at link time per #129; vt fields wired via post-decl chained
//     assigns rather than struct-lit, sidestepping #207 wholesale.
//     The pattern is the module-static analogue of memio.vstream.ww's
//     alloc-zero-chain.
//
//   - #209 (wwstage formattable match-arm bail when fmt imported):
//     log imports fmt transitively (via the formattable / field
//     types in vlogger's vtable + fmt.vfprint / vfprintf calls in
//     the std callbacks). All probe rows in test/wcc/779 run
//     STAGE_CS-only; eFinal closes the wwstage half when #209 lands.

package log;

import fmt;
import io;
import os;

// stderrsink_ctx — module-static state for the default vlogger's
// stderr sink. vt FIRST field for the intrusive vstream→*stderrsink_ctx
// cast in stderrwrite_v. Mirrors fmt.fd_ctx (fmt/vstream.ww:66) +
// memio.fixed_ctx (memio/vstream.ww:48); only scalars/ptrs beyond
// vt per ken's mandate.
type stderrsink_ctx = struct {
	vt: io.vtable,
	fd: i32,
};

// Zero-init at link time per #129 A.2/A.3 SSoT; ensureinit_v wires
// vt.reader / vt.writer + fd lazily on first dispatch. Same shape
// OLD log.ww uses for the pre-vtable stderrsink (log.ww:104).
let stderrsink_ctx_g: stderrsink_ctx;

// vlogger — V-side counterpart to OLD logger (log.ww:85). Same shape
// modulo the `_v` field-suffix (collapses on #50). Dispatchers route
// through io.vstream rather than *io.stream.
//
// Mirrors ref/hare/log/logger.ha:9.
export type vlogger = struct {
	println_v:  fn(l: *vlogger, args: fmt.formattable...) void,
	printfln_v: fn(l: *vlogger, format: str, fields: fmt.field...) void,
};

// vstdlogger — concrete vlogger forwarding to an io.vstream sink.
// First-field embed: `&sl.logger` yields a `*vlogger` (intrusive
// outer→inner cast); the vtable callback recovers the outer via
// `*vstdlogger` cast.
//
// Mirrors ref/hare/log/logger.ha:18 (stdlogger).
export type vstdlogger = struct {
	logger: vlogger,
	sink:   io.vstream,
};

// _silent_v / _default_v — backing storage for the silent_v /
// default_v *vlogger globals. Zero-init at link time; ensureinit_v
// fills the println_v / printfln_v slots.
let _silent_v:  vlogger;
let _default_v: vstdlogger;

// silent_v / default_v / global_v — Hare-style *vlogger globals.
// Zero-init at link time; lazily wired by ensureinit_v on the first
// call to any exported fn. Same divergence as OLD log.ww:116-118
// (header rationale for the lazy-init route applies wholesale: ww
// cstage emit_lets only constexprs primitive / str-literal /
// array-literal lets — struct- and pointer-literal init aren't
// reachable). #50 / eFinal graduates if static-init lands.
export let silent_v:  *vlogger;
export let default_v: *vlogger;
export let global_v:  *vlogger;

// initdone_v — guards ensureinit_v so the one-shot wiring runs once.
// Mirrors OLD initdone (log.ww:122) + lib/temp's rnginit pattern.
let initdone_v: i32 = 0;

fn ensureinit_v() void = {
	if (initdone_v != 0) { return; };
	stderrsink_ctx_g.fd = 2;
	stderrsink_ctx_g.vt.reader = (&stderrread_v):  *io.reader;
	stderrsink_ctx_g.vt.writer = (&stderrwrite_v): *io.writer;

	_silent_v.println_v  = silentprintln_v;
	_silent_v.printfln_v = silentprintfln_v;

	_default_v.logger.println_v  = stdprintln_v;
	_default_v.logger.printfln_v = stdprintfln_v;
	_default_v.sink = &stderrsink_ctx_g.vt;

	silent_v  = &_silent_v;
	default_v = &_default_v.logger;
	global_v  = default_v;
	initdone_v = 1;
};

// stderrread_v / stderrwrite_v — vtable callbacks for the private
// stderr sink. Read is eof-only — lib/log writes; never reads.
// Mirror of OLD stderrread / stderrwrite (log.ww:148-160) modulo the
// (size | io.eof | io.error) / (size | io.error) return surface;
// -errno collapses to a nomem-widened io.error per the
// fmt.fdsinkwrite_v precedent (fmt/vstream.ww:88-92).
fn stderrread_v(s: io.vstream, buf: []u8) (size | io.eof | io.error) = {
	let e: io.eof;
	return e;
};

fn stderrwrite_v(s: io.vstream, buf: []u8) (size | io.error) = {
	let c: *stderrsink_ctx = s: *stderrsink_ctx;
	let r: i64 = os.write(c.fd, buf.ptr, buf.len: u64);
	if (r < 0) {
		let nm: nomem;
		let e: io.error = nm;
		return e;
	};
	return r: size;
};

// stdprintln_v / stdprintfln_v — vtable callbacks for vstdlogger.
// Forwards to fmt.vfprint / vfprintf on the sink + appends the
// trailing newline via io.st_write. Hare's fmt.fprintln emits the
// newline inside one wrapper (ref/hare/fmt/wrappers.ha:60-68); we
// inline that split at the log site because fmt.vfprint is the bare
// (no-newline) primitive. The (size | io.error) results are dropped
// — lib/log's surface is `void` (matches Hare + OLD stdprintln at
// log.ww:167).
fn stdprintln_v(l: *vlogger, args: fmt.formattable...) void = {
	let sl: *vstdlogger = l: *vstdlogger;
	fmt.vfprint(sl.sink, args...);
	let nl: [1]u8;
	nl[0] = 10u8;
	let v: []u8 = nl[0:1];
	io.st_write(sl.sink, v);
};

fn stdprintfln_v(l: *vlogger, format: str, fields: fmt.field...) void = {
	let sl: *vstdlogger = l: *vstdlogger;
	fmt.vfprintf(sl.sink, format, fields...);
	let nl: [1]u8;
	nl[0] = 10u8;
	let v: []u8 = nl[0:1];
	io.st_write(sl.sink, v);
};

// silentprintln_v / silentprintfln_v — vtable callbacks for the
// silent vlogger. Discard every record without dispatching through
// fmt; keeps silent truly silent if fmt ever gets stateful. Mirror
// of OLD silentprintln / silentprintfln (log.ww:183-187).
fn silentprintln_v(l: *vlogger, args: fmt.formattable...) void = { };
fn silentprintfln_v(l: *vlogger, format: str, fields: fmt.field...) void = { };

// ---- public API (10 _v variants) -----------------------------------------

// new_v — build a vstdlogger over `sink`, returned BY VALUE (fold-eFinal
// PREP). Hare returns the stdlogger by value (ref/hare/log/logger.ha:20);
// the OLD out-parameter shape existed only because wide-struct sret was
// unimplemented — it now round-trips (test/wcc/925), so the constructor
// builds in a local and `return r;` (proven field-by-field sret form).
// vstdlogger is 24B (two fn-ptrs + sink), returned via the SysV memory
// class; the caller owns the returned logger (stack ownership, no-GC)
// and passes `&sl.logger` to the dispatch fns.
export fn new_v(sink: io.vstream) vstdlogger = {
	ensureinit_v();
	let r: vstdlogger;
	r.logger.println_v  = stdprintln_v;
	r.logger.printfln_v = stdprintfln_v;
	r.sink = sink;
	return r;
};

// lprintln_v — dispatch `args` through `log`. Mirrors OLD lprintln
// (log.ww:202) + ref/hare/log/funcs.ha:8.
export fn lprintln_v(log: *vlogger, args: fmt.formattable...) void = {
	ensureinit_v();
	log.println_v(log, args...);
};

// println_v — dispatch through the [[global_v]] vlogger. Mirrors
// OLD println (log.ww:208) + ref/hare/log/funcs.ha:18.
export fn println_v(args: fmt.formattable...) void = {
	ensureinit_v();
	lprintln_v(global_v, args...);
};

// lfatal_v — lprintln_v to `log` then exit(255). `never` return
// marks the bottom type so flow-control checks treat callers as
// terminated. Mirrors OLD lfatal (log.ww:216) +
// ref/hare/log/funcs.ha:28.
export fn lfatal_v(log: *vlogger, args: fmt.formattable...) never = {
	lprintln_v(log, args...);
	os.exit(255);
};

// fatal_v — lprintln_v to [[global_v]] then exit(255). Mirrors OLD
// fatal (log.ww:223) + ref/hare/log/funcs.ha:45.
export fn fatal_v(args: fmt.formattable...) never = {
	println_v(args...);
	os.exit(255);
};

// setlogger_v — install `log` as the [[global_v]] vlogger. Mirrors
// OLD setlogger (log.ww:230) + ref/hare/log/global.ha:20.
export fn setlogger_v(log: *vlogger) void = {
	ensureinit_v();
	global_v = log;
};

// lprintfln_v — dispatch a format-string record through `log`.
// Mirrors OLD lprintfln (log.ww:237) + ref/hare/log/funcs.ha:13.
export fn lprintfln_v(log: *vlogger, format: str, fields: fmt.field...) void = {
	ensureinit_v();
	log.printfln_v(log, format, fields...);
};

// printfln_v — dispatch through the [[global_v]] vlogger. Mirrors
// OLD printfln (log.ww:244) + ref/hare/log/funcs.ha:23.
export fn printfln_v(format: str, fields: fmt.field...) void = {
	ensureinit_v();
	lprintfln_v(global_v, format, fields...);
};

// lfatalf_v — lprintfln_v to `log` then exit(255). Mirrors OLD
// lfatalf (log.ww:251) + ref/hare/log/funcs.ha:35.
export fn lfatalf_v(log: *vlogger, format: str, fields: fmt.field...) never = {
	lprintfln_v(log, format, fields...);
	os.exit(255);
};

// fatalf_v — lprintfln_v to [[global_v]] then exit(255). Mirrors
// OLD fatalf (log.ww:258) + ref/hare/log/funcs.ha:52.
export fn fatalf_v(format: str, fields: fmt.field...) never = {
	printfln_v(format, fields...);
	os.exit(255);
};