# `tremolo/schemas`

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## Purpose

Zod schemas validating the construction-time options and preset payload of `TremoloPlugin`. These run at the public boundary so any malformed object — wrong waveform name, out-of-range rate, NaN depth — is rejected with `AUDIO_FX.INVALID_OPTIONS` or `AUDIO_FX.INVALID_PRESET` before it can corrupt runtime state.

Separating schemas from the plugin module lets `index.ts` re-export them so callers can introspect the option surface (for forms, RPC validation, or storybook controls) without importing the audio implementation.

## Features

- `TremoloWaveformSchema` — `z.enum(["sine", "triangle", "square"])` — used in both options and preset payloads.
- `TremoloPluginOptionsSchema` — validates the three optional construction fields with their documented ranges (`rate` 0.05..20 Hz, `depth` 0..1, `waveform` enum).
- `TremoloPresetDataSchema` — `.strict()` object carrying only `waveform`; extra fields are rejected.
- All numeric fields are `z.number().finite()` so `NaN` and `Infinity` cannot sneak through.

## Usage: Basic Example

```ts
import { TremoloPluginOptionsSchema } from "@suaveplan/audio-fx-plugin-tremolo";

const parsed = TremoloPluginOptionsSchema.parse({
    initialWaveform: "triangle",
});
```

## Usage: Advanced Example

```ts
import {
    TremoloPresetDataSchema,
    TremoloWaveformSchema,
} from "@suaveplan/audio-fx-plugin-tremolo";

// Validate a preset blob coming off the wire before applying it.
function safeApplyPreset(plugin: TremoloPlugin, payload: unknown) {
    const parsed = TremoloPresetDataSchema.safeParse(payload);
    if (!parsed.success) {
        log.warn("dropped bad tremolo preset", parsed.error.issues);
        return;
    }
    plugin.applyPreset({
        version: 1,
        parameters: {},
        presetData: parsed.data,
    });
}

const waveforms = TremoloWaveformSchema.options;
console.log(waveforms); // ["sine", "triangle", "square"]
```

## API Reference

- `TremoloWaveformSchema: z.ZodEnum<["sine", "triangle", "square"]>`
- `TremoloPluginOptionsSchema: z.ZodObject<{ initialRateHz?, initialDepth?, initialWaveform? }>`
- `TremoloPresetDataSchema: z.ZodObject<{ waveform: TremoloWaveform }, "strict">`

## Implementation Notes

`TremoloWaveformSchema` is exported as a named schema (not inlined) so the same value is reused by `TremoloPluginOptionsSchema.initialWaveform` and `TremoloPresetDataSchema.waveform`. That guarantees both validation paths agree byte-for-byte on the legal waveform set — adding a fourth waveform in a future revision is a one-line change in `schemas.ts`.

`TremoloPresetDataSchema` uses `.strict()` for the same reason as the other plugins: unknown fields almost always indicate a payload from a sibling plugin or a forwards-incompatible schema. Silent rejection at the boundary is much less harmful than partial application, which can leave the plugin in a half-restored state. The combined "waveform-must-be-known, payload-must-be-exact" stance keeps the preset surface stable across plugin versions.