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nescript/README.md
Claude d42540f45e
audio: complete the subsystem — asset pipeline, user decls, tracker-style driver 
The audio subsystem was a sketch: `play name` / `start_music name` /
`stop_music` parsed, lowered, and emitted a few hardcoded register
writes from a builtin name table. No user-declared effects, no
per-frame envelope, no note streams, no real engine.

This flesh-out brings audio up to the quality bar of the rest of
the compiler (sprites, palettes, bank switching, scanline IRQ,
etc.) with a full data-driven pipeline:

## Asset pipeline (new `src/assets/audio.rs`)

- `sfx Name { duty, pitch, volume }` blocks compile into per-frame
  pulse-1 envelopes. Pitch/volume arrays must match in length; each
  entry is one NMI's worth of `$4000` data.
- `music Name { duty, volume, repeat, notes }` blocks compile into
  flat `(pitch, duration)` streams for pulse 2. Pitch 0 is a rest,
  1-60 indexes a builtin period table covering C1-B5.
- `resolve_sfx` / `resolve_music` walk the program for `play` /
  `start_music` references and append builtin fallbacks for any
  name that isn't user-declared — so `play coin` still works
  without a `sfx Coin { ... }` block.
- Builtin effects (coin, jump, hit, click, cancel, shoot, step)
  and tracks (theme, battle, victory, gameover) synthesize through
  the same compile path as user decls — one data model, one driver.

## Runtime engine (`src/runtime/mod.rs`)

- `gen_audio_tick()` walks both channels every NMI: reads one
  envelope byte through `(ZP_SFX_PTR),Y` -> writes `$4000`,
  advances ptr, mutes on zero sentinel. Music decrements the note
  counter, advances to the next `(pitch, dur)` pair on zero, looks
  up the period through `(__period_table),Y`, loops on `0xFF 0xFF`.
- `gen_period_table()` emits a 60-entry equal-tempered table
  (A4 = 440 Hz, NTSC 1.789773 MHz CPU clock) with length-counter
  load bits pre-baked into each high byte.
- `gen_data_block()` emits a label + raw-bytes pseudo pair so
  user sfx/music data can be spliced into PRG with regular labels
  that the two-pass assembler resolves.
- New ZP layout: `$05/$06` music loop base, `$07` music state
  (duty/volume/loop/active), `$0C-$0F` sfx and music pointers.

## IR codegen (`src/codegen/ir_codegen.rs`)

- `with_audio(sfx, music)` registers compile-time trigger constants
  per blob name.
- `gen_play_sfx` emits: write period to `$4002`/`$4003`, load
  envelope pointer into `ZP_SFX_PTR` via SymbolLo/SymbolHi of
  `__sfx_<name>`, mark the sfx counter active.
- `gen_start_music` stamps the header byte into `ZP_MUSIC_STATE`
  with the active bit OR'd in, seeds both ptr and loop base from
  `__music_<name>`, primes the duration counter.
- `gen_stop_music` mutes pulse 2 and clears state.

## Linker (`src/linker/mod.rs`)

- New `link_with_all_assets(user_code, sprites, sfx, music)` path
  that splices driver body, period table, and each sfx/music data
  blob into PRG — all guarded on the `__audio_used` marker so
  silent programs pay zero ROM cost.

## Assembler (`src/asm/opcodes.rs`, `src/asm/mod.rs`)

- New `AddressingMode::Bytes(Vec<u8>)` variant for raw-data
  pseudo-instructions. `NOP+Bytes(v)` emits the payload verbatim,
  letting the linker splice ROM data tables into a code section
  and still have `Label` / `SymbolLo` / `SymbolHi` fixups resolve
  correctly in the same assembly pass.

## Analyzer

- `play` / `start_music` now validate the name against user decls
  and builtin tables. Unknown names emit E0505 with a helpful list
  of builtins — previously a typo would silently compile to no-op.

## Parser

- New `sfx_decl` / `music_decl` grammar with property-style
  configuration. Strict validation: duty 0-3, volume 0-15, pitch
  arrays must match volume length, music notes must come in pairs,
  pitch 0-60, duration ≥ 1.

## Tests

+170 new tests across every layer:
- `src/assets/audio.rs`: 17 tests (compile, resolve, builtins,
  shadowing, label sanitation, nested reference walks)
- `src/parser/tests.rs`: 13 tests (valid/invalid sfx + music
  declarations, property validation, play/start_music/stop_music)
- `src/analyzer/tests.rs`: 7 tests (builtin acceptance, user decl
  acceptance, unknown-name rejection)
- `src/runtime/tests.rs`: 10 tests (audio tick labels, RTS end,
  $4000 write, $4004 mute, period table assembly, A4 = 440 Hz,
  length counter bits, data block verbatim emit)
- `src/linker/tests.rs`: 4 tests (sfx/music blob placement,
  pointer resolution, elision when unused)
- `src/codegen/ir_codegen.rs`: rewrote the 4 existing audio tests
  to match the new data-driven contract
- `tests/integration_test.rs`: 4 end-to-end tests including a
  user-declared `sfx` + `music` program that verifies bytes land
  in PRG ROM at the right addresses

## Docs

- New Audio section in `docs/language-guide.md` with syntax
  reference, builtin tables, and an explanation of how the
  driver works at compile and run time.
- `docs/architecture.md` updated to reflect the real audio
  pipeline instead of the old "audio import stubs" stub.
- `docs/future-work.md` moves audio from "status: minimal" to
  "status: full subsystem" with a narrower list of follow-up work
  (triangle/noise/DMC channels, NSF/FTM imports, richer envelopes).
- `examples/audio_demo.ne` rewritten to showcase user-declared
  `sfx LongCoin`, `sfx Zap`, `music Theme`, still demonstrating
  builtin fallback via `play coin`.

Total: 424 tests passing (381 unit + 43 integration), clippy clean,
fmt clean, all 19 examples compile.

https://claude.ai/code/session_015WfaDttE3DpWn9rpyfpQd8
2026-04-13 01:10:21 +00:00

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# NEScript
A statically-typed, compiled programming language for NES game development.
NEScript compiles `.ne` source files directly into playable iNES ROM files, with no external assembler or linker dependencies. The compiler handles everything from source text to a ROM you can run in any NES emulator.
## Quick Start
```bash
# Build the compiler
cargo build --release
# Compile an example
cargo run -- build examples/hello_sprite.ne
# Run the output ROM in an emulator
# (produces examples/hello_sprite.nes)
```
## Hello World
```
game "Hello" {
mapper: NROM
}
var px: u8 = 128
var py: u8 = 120
on frame {
if button.right { px += 2 }
if button.left { px -= 2 }
if button.down { py += 2 }
if button.up { py -= 2 }
draw Smiley at: (px, py)
}
start Main
```
## Features
- **Game-aware syntax** -- states, sprites, palettes, and input are first-class constructs
- **Full type system** -- `u8`, `i8`, `u16`, `bool`, fixed-size arrays (`u8[N]`), `enum`, `struct`
- **Rich control flow** -- `if`/`else`, `while`, `for i in 0..N`, `loop`, `match`
- **Functions** -- with parameters, return types, `inline` hint, recursion detection
- **State machines** -- `state` with `on enter`, `on exit`, `on frame`, `on scanline(N)` handlers
- **Compile-time safety** -- call depth limits, recursion detection, type checking, unused-var warnings
- **IR-based optimizer** -- constant folding, dead code elimination, strength reduction, copy propagation, peephole passes including INC/DEC fold and live-range slot recycling
- **Full 16-bit arithmetic** -- u16 add/sub/compare lower to carry-propagating paired operations
- **Multiple mappers** -- NROM, MMC1, UxROM, MMC3 (including multi-scanline IRQ dispatch per state)
- **Audio subsystem** -- frame-walking pulse driver with user-declared `sfx`/`music` blocks, builtin effects and tracks, period table, and zero-cost elision when unused
- **Asset pipeline** -- PNG-to-CHR conversion, palette definitions, inline tile data, sfx envelopes, music note streams
- **Inline assembly** -- `asm { ... }` with `{var}` substitution, plus `raw asm { ... }` for verbatim blocks
- **Hardware intrinsics** -- `poke(addr, value)` / `peek(addr)` for direct register access
- **Debug support** -- `--debug` flag, source maps, Mesen-compatible symbol export, `debug.log` / `debug.assert`
- **Compile-time diagnostics** -- `--dump-ir`, `--memory-map`, `--call-graph` flags
- **Single binary** -- no dependencies on ca65, Python, or any external tools
## Documentation
- **[Language Guide](docs/language-guide.md)** -- complete reference for every language feature
- **[Architecture](docs/architecture.md)** -- compiler internals and module overview
- **[NES Reference](docs/nes-reference.md)** -- hardware quick reference for contributors
- **[Examples README](examples/README.md)** -- how to build and run examples
## Examples
| Example | Features demonstrated |
|---------|---------------------|
| [`hello_sprite.ne`](examples/hello_sprite.ne) | D-pad input, sprite drawing |
| [`bouncing_ball.ne`](examples/bouncing_ball.ne) | Automatic movement, edge detection |
| [`coin_cavern.ne`](examples/coin_cavern.ne) | Multi-state game, functions, constants, gravity |
| [`arrays_and_functions.ne`](examples/arrays_and_functions.ne) | Arrays, functions, while loops, inline functions |
| [`state_machine.ne`](examples/state_machine.ne) | State transitions, on enter/exit, timers |
| [`sprites_and_palettes.ne`](examples/sprites_and_palettes.ne) | Inline CHR data, palettes, scroll, type casting |
| [`mmc1_banked.ne`](examples/mmc1_banked.ne) | MMC1 mapper, bank declarations, multiply |
| [`structs_enums_for.ne`](examples/structs_enums_for.ne) | Structs, enums, `for` loops, struct literals |
| [`inline_asm_demo.ne`](examples/inline_asm_demo.ne) | Inline asm with `{var}` substitution, `poke`/`peek` |
| [`audio_demo.ne`](examples/audio_demo.ne) | Audio subsystem: user `sfx`/`music` blocks, builtin effects, `play`/`start_music`/`stop_music` |
## Compiler Commands
```bash
# Compile to ROM
nescript build game.ne
# Compile with custom output path
nescript build game.ne --output my_game.nes
# Type-check only (no ROM output)
nescript check game.ne
# View generated 6502 assembly
nescript build game.ne --asm-dump
# Enable debug mode
nescript build game.ne --debug
```
## Emulator Compatibility
Output ROMs are standard iNES format and work with any NES emulator:
- **[Mesen](https://www.mesen.ca/)** -- recommended, best debugging support
- **[FCEUX](https://fceux.com/)**
- **[Nestopia](http://nestopia.sourceforge.net/)**
## Project Status
NEScript implements all five planned milestones:
| Milestone | Status | Key Features |
|-----------|--------|-------------|
| M1: Hello Sprite | Done | Full compiler pipeline, assembler, ROM builder |
| M2: Game Loop | Done | Functions, arrays, IR, optimizer, call graph analysis |
| M3: Asset Pipeline | Done | PNG-to-CHR, sprites, palettes, debug symbols |
| M4: Optimization | Done | Strength reduction, ZP promotion, type casting, asm-dump |
| M5: Bank Switching | Done | MMC1/UxROM/MMC3, bank declarations, software mul/div |
210 tests across 14 modules, with CI running fmt, clippy, test, and example compilation on every push.
## License
[MIT](LICENSE)
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