jiwa 0.1.0

Terminal text reveal animations — typewriter + per-grapheme fade-in + pulse. Renderer-agnostic: returns plain RGB so the caller maps to crossterm, ratatui, or its own ANSI writer.
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# jiwa

[![crates.io](https://img.shields.io/crates/v/jiwa.svg)](https://crates.io/crates/jiwa)
[![docs.rs](https://img.shields.io/docsrs/jiwa)](https://docs.rs/jiwa)
[![CI](https://github.com/kako-jun/jiwa/actions/workflows/ci.yml/badge.svg)](https://github.com/kako-jun/jiwa/actions/workflows/ci.yml)

Terminal text **reveal** animations for Rust. Two small primitives:

- **Typewriter + per-grapheme fade-in** — characters appear one at a
  time and bloom from one color into another.
- **Pulse** — a single symbol "breathes" between two colors on a
  sinusoidal cycle, useful as a "now playing" / "thinking" indicator.

Both primitives are **renderer-agnostic**: they return plain `Rgb(u8, u8, u8)`
triples plus the text to draw, and you map those to whatever your
renderer already uses (`crossterm`, `ratatui`, raw ANSI, etc.). They are
also **pure** — every time-bearing call takes an explicit
`std::time::Instant`, so there is no global clock, no spawned thread,
and tests can advance time without sleeping.

The name is from the Japanese onomatopoeia **「じわじわ」** — something
appearing slowly, blooming into view.

## Install

```toml
[dependencies]
jiwa = "0.1"
```

## Example: typewriter reveal

```rust
use std::time::{Duration, Instant};
use jiwa::{RevealHandle, RevealOpts};

let start = Instant::now();
let reveal = RevealHandle::start_at("Hello, 世界", RevealOpts::default(), start);

// Tick once per redraw — your event loop chooses the cadence.
let frame = reveal.snapshot(start + Duration::from_millis(100));
for g in &frame {
    // g.text:    the grapheme cluster to draw
    // g.color:   Rgb(u8, u8, u8) to draw it in
    // g.progress: 0.0 (just appeared) .. 1.0 (fade complete)
    print!("{}", g.text);
}
```

The default preset (`RevealOpts::soft_green`) is tuned for problem /
quiz text on a dark terminal — 45 ms typewriter step, 320 ms fade from
a deep gray to a soft green so the in-between color reads as an
afterimage rather than a blink.

You can also disable either dimension by zeroing it:

- `char_interval = 0` → whole block fades in together (no typewriter).
- `fade_duration = 0` → pure typewriter, each grapheme appears at its
  final color.

## Example: pulse

```rust
use jiwa::{PulseHandle, PulseOpts};

let pulse = PulseHandle::start("♪", PulseOpts::default());
let frame = pulse.snapshot(std::time::Instant::now());
// frame.text == "♪"
// frame.color cycles between PulseOpts::color_dim and color_bright.
```

The default preset (`PulseOpts::cyan_breath`) gives a ~1.5 s breath
cycle from a muted teal to a bright cyan, designed for the "♪ audio
playing" affordance.

## Mapping to your renderer

`jiwa::Rgb` is intentionally not a wrapper around `crossterm::style::Color`
or `ratatui::style::Color`. Map at the call site:

```rust
// ratatui
let color = ratatui::style::Color::Rgb(g.color.0, g.color.1, g.color.2);

// crossterm
let color = crossterm::style::Color::Rgb { r: g.color.0, g: g.color.1, b: g.color.2 };
```

## Concurrency note

These primitives are pure functions of `(time, text, opts)`. They do
not own a thread, do not poll for input, and do not sleep. Anything
your reveal-in-progress UI needs to do concurrently (accept input
during the reveal, abort early, restart) is the responsibility of the
surrounding event loop — `jiwa` just answers "what does the frame look
like right now?".

## Status

- **v0.1.0** — library primitives extracted from
  [type-globe](https://github.com/kako-jun/type-globe)'s in-tree
  `jiwa_core` module (where they have been used in production since
  v0.6.0).
- **Planned**: a `jiwa` CLI binary so the same reveal/pulse engine is
  usable from shell pipes (`echo "Hello" | jiwa --fade 200ms`).
  Tracked in the repo issues.

## Inspiration

The CLI direction takes cues from
[TerminalTextEffects](https://github.com/ChrisBuilds/terminaltexteffects)
(Python). `jiwa` is intentionally narrower — reveal-shaped effects
only, Unix-pipe friendly, Rust single binary.

## License

MIT