# `schemas`

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## Purpose

The `gate.schemas` module owns the Zod boundary guards for `GatePlugin` — construction options and the plugin-specific preset payload. Every public input runs through these schemas before the plugin touches any state; failures surface as `AUDIO_FX.INVALID_OPTIONS` / `AUDIO_FX.INVALID_PRESET` with the Zod issue list in `context.issues`.

Keeping the schemas in a sibling folder follows the package-wide convention: hosts can import the schemas directly, run their own `safeParse` against UI input, and surface field-level errors before constructing a `GatePlugin`.

## Features

- `GatePluginOptionsSchema` — every field optional, ranged to match the parameter declarations in `gate.ts`: `threshold ∈ [-80, 0] dB`, `attack ∈ [0.1, 100] ms`, `hold ∈ [0, 500] ms`, `release ∈ [1, 1000] ms`.
- `GatePresetDataSchema` — `z.object({}).strict()`. The gate has no plugin-specific state beyond its automatable parameters; the universal `parameters` map carries everything that round-trips.

## Usage: Basic Example

```ts
import { GatePluginOptionsSchema } from "@suaveplan/audio-fx-plugin-gate";

const parsed = GatePluginOptionsSchema.safeParse(formValues);
if (!parsed.success) {
    return showFieldErrors(parsed.error.issues);
}
const gate = new GatePlugin(parsed.data);
```

## Usage: Advanced Example

```ts
import {
    GatePluginOptionsSchema,
    GatePresetDataSchema,
} from "@suaveplan/audio-fx-plugin-gate";

// Validate an untrusted preset payload from a shared template
// library before applyPreset. The plugin would catch the same issue,
// but the host wants a friendlier error before a plugin instance is
// constructed.
const result = GatePresetDataSchema.safeParse(payload.data);
if (!result.success) {
    return reject("Gate preset is corrupt.");
}
```

## API Reference

- `GatePluginOptionsSchema` — `z.ZodObject` matching `GatePluginOptions`. All fields optional and ranged.
- `GatePresetDataSchema` — strict empty object; rejects any unknown keys.

## Implementation Notes

`GatePluginOptionsSchema` uses `.finite()` on every numeric field so `NaN` and `±Infinity` are rejected at the boundary; the one-pole envelope follower's `exp(-1 / (τ · sr))` calculation would otherwise propagate non-finite coefficients into the smoothing state and contaminate every subsequent block.

`attack.min(0.1)` and `release.min(1)` match the parameter declarations; values smaller than this break the one-pole smoothing assumption (the coefficient approaches `1` from below) and produce numerical artefacts in single-precision float. `hold.min(0)` allows a zero-hold gate (closes immediately when the envelope drops), which is useful for hyper-tight drum gates.

`threshold.min(-80)` covers the practical noise floor of consumer audio; values below `-80 dB` are effectively "gate never closes" and don't need their own UI affordance. The upper bound at `0 dB` is the maximum useful threshold — at `0 dB` the gate is essentially always closed since real-world signals rarely exceed `0 dBFS`.

The strict empty `GatePresetDataSchema` rejects any unknown keys so a stale preset format with phantom fields fails loud rather than silently dropping data.