# `distortion/schemas`

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## Purpose

Zod schemas validating the construction-time options and preset payload of `DistortionPlugin`. These run at the public boundary so any malformed object — wrong mode name, out-of-range drive, non-integer bit depth, NaN gain — 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

- `DistortionModeSchema` — `z.enum(["waveshaper", "bitcrusher", "overdrive"])` — used in both options and preset payloads.
- `DistortionPluginOptionsSchema` — validates all four optional construction fields with their documented ranges (`drive` 0..40 dB, `bits` 1..16 integer, `outputGain` ±24 dB).
- `DistortionPresetDataSchema` — `.strict()` object carrying only `mode`; extra fields are rejected.
- `bits` is `z.number().int()` so float bit-depths (which would round unpredictably) cannot sneak through.

## Usage: Basic Example

```ts
import { DistortionPluginOptionsSchema } from "@suaveplan/audio-fx-plugin-distortion";

const parsed = DistortionPluginOptionsSchema.parse({
    initialMode: "waveshaper",
});
```

## Usage: Advanced Example

```ts
import {
    DistortionModeSchema,
    DistortionPresetDataSchema,
} from "@suaveplan/audio-fx-plugin-distortion";

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

const modes = DistortionModeSchema.options;
console.log(modes); // ["waveshaper", "bitcrusher", "overdrive"]
```

## API Reference

- `DistortionModeSchema: z.ZodEnum<["waveshaper", "bitcrusher", "overdrive"]>`
- `DistortionPluginOptionsSchema: z.ZodObject<{ initialMode?, initialDriveDb?, initialBitDepth?, initialOutputGainDb? }>`
- `DistortionPresetDataSchema: z.ZodObject<{ mode: DistortionMode }, "strict">`

## Implementation Notes

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

`DistortionPresetDataSchema` 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, and silent rejection at the boundary is much less harmful than partial application. The combined "mode-must-be-known, payload-must-be-exact" stance keeps the preset surface stable across plugin versions.