# Input & output formats

See [`architecture.md`](architecture.md) for how these fit together.
There are two ways to provide input (direct CLI flags, or `run-engine.sh`
+ `user.properties`) and three output formats (`text`, `html`, `json`); the
`DailyReading` struct is the programmatic form all three are rendered
from, and the one watch UI code consumes directly. `json` is also
`interpreter-cli`'s input format — see "The interpreter" at the bottom
of this file, which supports the same three output formats (and the
same `--lang`) for its own report, independently of `deck-engine`.

## Input

### Direct CLI flags (`dist/deck-engine`)

```
deck-engine --seed <string> --birth-date YYYY-MM-DD --birth-time HH:MM
            --birth-utc-offset <hours> --birth-lat <deg> --birth-lon <deg>
            [--date YYYY-MM-DDTHH:MM] [--format text|html|json]
```

| Flag | Required | Format | Meaning |
|---|---|---|---|
| `--seed` | yes | any string | Tarot seed. The same seed always produces the same 10-card spread, positions, and orientations (see `rng.c`/`tarot.c`). |
| `--birth-date` | yes | `YYYY-MM-DD` | Birth date, local calendar. |
| `--birth-time` | yes | `HH:MM` (24h) | Birth time, local clock. |
| `--birth-utc-offset` | yes | decimal hours, e.g. `2` or `-5.5` | Hours to **subtract** from local birth time to get UTC (e.g. `2` for CEST). |
| `--birth-lat` | yes | decimal degrees | Birth latitude, north positive. |
| `--birth-lon` | yes | decimal degrees | Birth longitude, east positive. |
| `--date` | no | `YYYY-MM-DDTHH:MM[:SS]` | UTC moment used for today's transits and as the moment the tarot seed is drawn against. Defaults to the current system time. |
| `--format` | no | `text` \| `html` \| `json` | Output format, defaults to `text`. `json` always uses language-independent identifiers, ignoring `--lang`. |
| `--lang` | no | language code, e.g. `en`, `de` | Reading language, defaults to `en`. Matches a file named `<code>.lang` in `--i18n-dir` (see "Translations" below). Unknown codes or missing files fall back to English with a warning on stderr. |
| `--i18n-dir` | no | path | Directory to look for `<lang>.lang` in. Defaults to an `i18n/` directory next to the binary itself (resolved from `argv[0]`, so `dist/deck-engine` finds `dist/i18n/` regardless of the caller's working directory). |

Birth latitude/longitude only affect the Ascendant/houses — planet signs
are geocentric and location-independent.

### `run-engine.sh` + `user.properties`

`dist/run-engine.sh [text|html|json] [lang]` wraps the binary for daily
use:

- **Seed and `--date`** come from the OS clock: `date +%Y-%m-%d` (stable
  all day) and `date -u +%Y-%m-%dT%H:%M`.
- **Birth data and language** are read from `dist/user.properties`, a
  `key=value` properties file next to the script (`#`-prefixed lines and
  blank lines are comments; whitespace around `=` is trimmed):

  ```properties
  birth_date=1990-05-14
  birth_time=14:32
  birth_utc_offset=2
  birth_lat=52.5200
  birth_lon=13.4050
  lang=en
  ```

  The file is seeded once from `engine/scripts/user.properties.template`
  with placeholder values (`YOUR_BIRTH_DATE_HERE`, etc.). `run-engine.sh`
  checks every birth field for an empty value or a leftover `YOUR_`
  placeholder and refuses to run with a clear error until the file is
  filled in; `lang` has no such check since it always has a usable
  default (`en`). Since `dist/` itself can be wiped (`make clean`, or
  deleting the directory), the build also keeps a durable backup at
  `engine/scripts/user.properties.local` (gitignored) once the file
  looks filled in, and restores from it if `dist/user.properties` is
  ever missing — see `CLAUDE.md`'s "Build & run".
- The optional second argument overrides `lang=` for a single run without
  editing the file, e.g. `dist/run-engine.sh html de`.
- `dist/run-interpreter.sh` (no arguments) is the equivalent wrapper for
  the interpreter: same OS clock + `user.properties` inputs, but calls
  `deck-engine --format json` and pipes it straight into
  `dist/interpreter-cli` — see "The interpreter" below.

### Translations (`--lang`, `dist/i18n/`)

Every piece of display text — planet/sign/moon-phase/aspect names, tarot
card names and meanings, Celtic Cross position names, and the section
headers in the `text`/`html` output — is looked up in a translation
catalog with the built-in English text as the fallback for any key the
catalog doesn't have. See `CLAUDE.md`'s "Translations" section for the
key-naming convention and how to add a new language.

`engine/i18n/en.lang` and `de.lang` are the shipped translation files;
`make` copies `engine/i18n/*.lang` to `dist/i18n/` (refreshed on every
build, like `dist/img/`). Adding a language is just dropping another
`<code>.lang` file into `engine/i18n/` — no code changes needed.

## Output

### `DailyReading` (the real output — `reading.h`)

`reading_generate()` is the actual API; `text`/`html` below are just two
ways of rendering the struct it fills in. This is what watch UI code
reads directly.

```c
typedef struct {
  NatalChart natal;
  DailyTransits transits;
  CelticCrossSpread spread;
} DailyReading;
```

- **`NatalChart`** (`astro.h`): `bodies[10]` (Sun..Pluto, each a sign +
  degree-in-sign + raw ecliptic longitude + whole-sign `house` 1-12),
  `ascendant_longitude`, `houses[12]` (whole-sign: `houses[0]` is the
  Ascendant's sign).
- **`DailyTransits`** (`astro.h`): `bodies[10]` (today's positions, same
  shape as above — `house` here is the natal chart's house the
  transiting planet currently occupies, not a fresh "houses for right
  now" chart), `moon_phase` (one of 8 named phases), `aspects[]` +
  `aspect_count` (each aspect names a transiting planet, a natal planet,
  an `AspectType` — conjunction/sextile/square/trine/opposition — and
  the orb in degrees).
- **`CelticCrossSpread`** (`tarot.h`): `positions[10]`, indexed by
  `CelticCrossPosition` (Present, Challenge, Crown, Foundation, Recent
  Past, Near Future, Attitude, Environment, Hopes and Fears, Outcome —
  Waite's own drawing order), each holding a `TarotCard` and a `reversed`
  bool.

### `--format text`

Four `=====`-delimited sections, in order: natal chart (each body's sign
+ degree + house, then the Ascendant), today's sky (Moon phase, then each
body's transiting position + the natal house it currently occupies),
today's aspects to the natal chart (one line per aspect, with orb), and
the Celtic Cross (one block per position: name, card, `(Reversed)` if
applicable, the position's meaning, then the card's meaning).

```
===== Natal Chart =====
Sun       23.5° Taurus      (House 3)
Moon      15.2° Capricorn   (House 11)
...
Ascendant  18.4° Pisces

===== Today's Sky =====
Moon phase: Waning Gibbous
Sun       11.5° Cancer      (House 5)
...

===== Today's Aspects to Natal Chart =====
Transiting Sun Opposition natal Moon (orb 3.7°)
...

===== Celtic Cross =====
The Present      The High Priestess (Reversed)
  This covers him: the general influence affecting the matter.
  Passion, moral or physical ardour, conceit, surface knowledge.
...
```

### `--format html`

A single self-contained HTML page (inline `<style>`, no JS, no external
requests) with the same four sections, plus each of the 10 Celtic Cross
cards rendered as an image:

```html
<img class="reversed" src="img/RWS_Tarot_02_High_Priestess.jpeg" alt="The High Priestess">
```

- `src="img/<file>"` is relative to the **HTML file's own location** —
  it expects to sit next to an `img/` directory, exactly like
  `dist/reading.html` next to `dist/img/` (which `make images` populates
  from `res/img/`). Saving the HTML output anywhere else breaks the
  image links.
- Reversed cards get `class="reversed"`, styled with `transform:
  rotate(180deg)` in the page's inline CSS.

### `--format json`

A single JSON object mirroring `DailyReading` exactly — `natal`,
`transits`, `spread` — using the **slug** accessors
(`astro_body_slug()`, `astro_sign_slug()`, `astro_moon_phase_slug()`,
`astro_aspect_slug()`, `tarot_card_slug()`, `tarot_position_slug()`)
rather than the display-name ones, so the output is identical regardless
of `--lang` — this is the one format meant for another program to parse
(`dist/interpreter-cli`, see "The interpreter" below), not for a human to
read.

```json
{
  "natal": {
    "bodies": [
      {"body": "sun", "sign": "taurus", "degree_in_sign": 23.4926, "ecliptic_longitude": 53.4926, "house": 3},
      ...
    ],
    "ascendant_longitude": 348.4123,
    "houses": ["pisces", "aries", ...]
  },
  "transits": {
    "bodies": [
      {"body": "sun", "sign": "cancer", "degree_in_sign": 11.5012, "ecliptic_longitude": 101.5012, "house": 5},
      ...
    ],
    "moon_phase": "waning_gibbous",
    "aspects": [
      {"transiting_planet": "sun", "natal_planet": "moon", "type": "opposition", "orb": 3.7021},
      ...
    ]
  },
  "spread": {
    "positions": [
      {"position": "present", "card": "high_priestess", "reversed": true},
      ...
    ]
  }
}
```

- `bodies` is always `NUM_BODIES` (10) entries, Sun..Pluto in `Body` enum
  order; `spread.positions` is always `TAROT_SPREAD_SIZE` (10) entries in
  `CelticCrossPosition` enum order (Present, Challenge, Crown,
  Foundation, Recent Past, Near Future, Attitude, Environment, Hopes and
  Fears, Outcome — see `CLAUDE.md`'s "Tarot" section for why that's not
  the order most tutorials use).
- `natal.houses[i]` is the sign occupying whole-sign house `i + 1`;
  `houses[0]` is the Ascendant's own sign. `transits.bodies[*].house` is
  a house number (1-12) into the **natal** chart, not a fresh "houses for
  right now" chart — same rule as the `text`/`html` output.
- All angles are decimal degrees, `%.4f`. `aspects` may be an empty array
  (a valid "no aspects today"), but the key itself is always present.

## The interpreter (`interpreter/`, `dist/interpreter-cli`)

`dist/interpreter-cli` is a separate binary — see `CLAUDE.md`'s
"Interpretation" section for the full architecture — that reads a
`--format json` document and scores how significant today's transits
are. It never links `astro.c`/`tarot.c`/`reading.c` (or the vendored
Astronomy Engine) — only `engine/src/tarot_data.c`/`i18n.c` are linked
in, for real card/position names and Waite meaning text (see
`CLAUDE.md`'s `INTERP_TAROT_TEXT_OBJS` note). Otherwise it depends only
on the JSON shape above.

Like `deck-engine`, its own output supports `--format text|html|json`
and `--lang <code>`/`--i18n-dir <path>`:

| Flag | Required | Format | Meaning |
|---|---|---|---|
| `[reading.json]` | no | file path or `-` | Input file; stdin (or `-`) if omitted. |
| `--format` | no | `text` \| `html` \| `json` | This binary's **own output** format, defaults to `text`. Entirely independent of the `--format json` that produced its *input* - see below. |
| `--lang` | no | language code, e.g. `en`, `de` | This binary's **own output** language, defaults to `en`. Same `<code>.lang`/`--i18n-dir` convention as `deck-engine` (see "Translations" above) - `main.c` calls `i18n_load()` itself, so `narrative.c`'s/`guidance.c`'s own text (in `engine/i18n/*.lang` under `narrative.*`/`guidance.*` keys) is translated too, not just the card/position/body/sign/aspect vocabulary it shares with `deck-engine`. |
| `--i18n-dir` | no | path | Same convention as `deck-engine`'s: defaults to an `i18n/` directory next to this binary. |

**This `--lang` is unrelated to whatever `--lang` `deck-engine` was run
with to produce the `--format json` input** - that JSON is always
language-independent (slugs only, see above), so it doesn't matter what
language `deck-engine` printed anything in, or whether it was even asked
to print anything at all (`--format json` never touches `--lang`
either). The two `--lang` flags, on the two sides of the pipe, are
independent settings.

```bash
dist/deck-engine ... --format json | dist/interpreter-cli --format html --lang de
# or:
dist/deck-engine ... --format json > reading.json
dist/interpreter-cli --format json reading.json
# or, for daily use (OS clock + user.properties, same inputs as run-engine.sh,
# including user.properties' lang=):
dist/run-interpreter.sh              # text output, language from user.properties
dist/run-interpreter.sh html de      # override format/language for this run
```

- **Input**: a file path argument, or stdin if no argument (or `-`) is
  given. `"transits"."aspects"` is required (an empty array is valid and
  means "no notable transits today"; a missing key is treated as invalid
  input) and drives scoring. `"natal"."bodies"`/`"transits"."bodies"` are
  read too, for the sign/house context printed alongside each event below
  (not for scoring), and `"spread"."positions"` is read for the full
  Celtic Cross readout and the guidance paragraph below — an entry naming
  an unrecognized body/card/position, a missing `house`, or a missing
  `"spread"` key entirely is silently skipped/zeroed rather than failing
  the load (see `parse_bodies()`/`parse_spread()` in `reading_io.c`).
- **Input**: same for all three output formats above - only how the
  parsed data gets rendered differs.

### `--format text`

A plain-text report, printed in a fixed order —
  1. the day's overall significance level (`Quiet`/`Notable`/
     `Significant`/`Major`, plus its rank out of the 4 defined levels,
     e.g. `Notable (2/4)`), with a "worth a deeper Celtic Cross look"
     line on `Major` days only;
  2. up to 5 of today's aspects ranked by score, each naming the sign
     and natal house the transiting planet currently occupies and the
     sign and house of the natal planet it's aspecting, followed by a
     short narrative sentence about what that transiting planet
     classically signifies *and which area of life its current house
     governs* (see `CLAUDE.md`'s `narrative.c` bullet) — omitted only if
     the source material has nothing to say for that planet/aspect
     combination;
  3. the full 10-position Celtic Cross spread, in Waite's own drawing
     order, each with its card (and orientation), the position's own
     description, and that card's actual meaning;
  4. finally, a guidance paragraph tying the day's top transit to the
     spread's Attitude/Outcome cards, with its opening sentence tailored
     to `day_level` (stronger wording on `Major`, softer on
     `Quiet`/`Notable`, falling back to a transit-free reading of the
     Attitude card alone on a day with no aspects at all) and, for the
     Attitude/Outcome cards it names, their actual Waite meaning for the
     orientation they landed in — see `CLAUDE.md`'s `guidance.c` bullet.
     This is printed last, as the closing takeaway after the reader has
     seen the full spread it references.

```
Day significance: Major (4/4)
(a major transit today - worth a deeper Celtic Cross look)

Top 5 significant transits:
  1. Transiting Pluto in Aquarius (house 3) Conjunction natal Moon in Aquarius (house 3) (orb 2.9°, score 9.60)
     In matters of communication, siblings, and everyday learning (house 3). Brings deep, often hidden transformation - the surfacing or dismantling of something that has outgrown its old form.
  2. Transiting Neptune in Aries (house 5) Sextile natal Moon in Aquarius (house 3) (orb 2.5°, score 9.25)
     In matters of romance, creativity, and children (house 5). Brings a state of chaos and confusion - an involved, uncertain condition of affairs, with plots, subtlety, or unseen influences at work.
  3. Transiting Uranus in Gemini (house 7) Trine natal Moon in Aquarius (house 3) (orb 2.0°, score 8.96)
     In matters of partnerships and close relationships (house 7). Brings separations, estrangements, sudden dislocations and violent upsets. Success through official or civic channels, and beneficial changes or appointments, are possible.

Celtic Cross:
  1. The Present: The Emperor (Reversed)
     This covers him: the general influence affecting the matter.
     Benevolence, compassion, credit; also confusion to enemies, obstruction, immaturity.
  2. The Challenge: The Devil
     This crosses him: the nature of the obstacle in the matter.
     Ravage, violence, vehemence, extraordinary efforts, force, fatality.
  ...
  7. Himself: The Magician
     His position or attitude in the circumstances.
     Skill, diplomacy, address, subtlety; self-confidence, will.
  ...
  10. The Outcome: Strength
     What will come: the final result of the matter.
     Power, energy, action, courage, magnanimity; complete success and honours.

With Pluto as today's dominant influence: Today concentrates whatever you already
bring to it - your current approach will be amplified, so make sure it's the one
you want.
Your Attitude card is The Magician: Skill, diplomacy, address, subtlety; self-confidence, will.
The spread's likely Outcome is Strength: Power, energy, action, courage, magnanimity; complete success and honours.
```

On a quieter day, only the opening of the guidance paragraph changes:

```
Day significance: Notable (2/4)
...
With a mild touch from Jupiter today: Your instincts are sound, but the day is
testing them - hold your position without forcing the issue.
Your Attitude card is The Sun: Material happiness, fortunate marriage, contentment.
The spread's likely Outcome is Justice: Equity, rightness, probity, executive; triumph of the deserving side in law.
```

The same report with `--lang de` (same input as the Major example
above):

```
Bedeutung des Tages: Einschneidend (4/4)
(ein einschneidender Transit heute - ein genauerer Blick auf das Keltische Kreuz lohnt sich)

Top 5 wichtige Transits:
  1. Transit Pluto in Wassermann (Haus 3) Konjunktion natal Mond in Wassermann (Haus 3) (Orbis 2.9°, Punktzahl 9.60)
     In Fragen von Kommunikation, Geschwistern und alltäglichem Lernen (Haus 3). Bringt tiefgreifenden, oft verborgenen Wandel - das Auftauchen oder die Auflösung von etwas, das seine alte Form überwachsen hat.
  ...

Keltisches Kreuz:
  1. Die Gegenwart: Der Herrscher (Umgekehrt)
     Dies bedeckt ihn: der allgemeine Einfluss, der die Angelegenheit betrifft.
     Wohlwollen, Mitgefühl, Ansehen; auch Verwirrung der Feinde, Behinderung, Unreife.
  ...

Pluto ist heute der bestimmende Einfluss: Der heutige Tag verstärkt, was du bereits
mitbringst - deine derzeitige Herangehensweise wird verstärkt, also stelle sicher,
dass es die richtige ist.
Deine Haltungskarte ist Der Magier: Geschick, Diplomatie, Gewandtheit, Feinsinn; Selbstvertrauen, Wille.
Das wahrscheinliche Ergebnis des Blatts ist Kraft: Macht, Energie, Tatkraft, Mut, Großmut; voller Erfolg und Ehren.
```

### `--format html`

A single self-contained HTML page, same inline-CSS/no-JS approach as
`deck-engine`'s own `--format html`, and the same three sections as text
(significant transits as a table, the full Celtic Cross as an image
grid, guidance as a closing callout) - reusing the exact same
`img/<file>` card-art convention (`tarot_card_image_file()`), so it
expects to sit next to an `img/` directory just like `deck-engine`'s
HTML output:

```html
<div class="card">
  <div class="position">The Present</div>
  <img class="reversed" src="img/RWS_Tarot_04_Emperor.jpeg" alt="The Emperor">
  <div class="name">The Emperor (Reversed)</div>
  <div class="desc">This covers him: the general influence affecting the matter.</div>
  <div class="meaning">Benevolence, compassion, credit; also confusion to enemies, obstruction, immaturity.</div>
</div>
```

The guidance section renders as one `<p>` per line of the same text
`--format text` prints last (intro sentence, Attitude line, Outcome
line), inside a `<div class="guidance">`.

### `--format json`

Unlike `deck-engine`'s own `--format json` - which is deliberately
**language-independent** (slugs only, no `--lang`-dependent prose, since
it's a machine interchange format between the two binaries) -
`interpreter-cli`'s `--format json` embeds the *same localized
narrative/guidance prose* `--format text` prints, in whatever `--lang`
was loaded, **alongside** stable, language-independent slug fields. This
is a deliberate difference: rendering that prose is this module's whole
job, so a JSON consumer that wants it doesn't have to reimplement
`narrative.c`/`guidance.c`'s logic itself - but a consumer that only
wants structured data (e.g. watch UI code with its own rendering) still
has the slugs to work with directly.

```json
{
  "day_significance": {
    "level": "major",
    "rank": 4,
    "count": 4,
    "deserves_framing": true
  },
  "significant_transits": [
    {
      "transiting_planet": "pluto",
      "transiting_sign": "aquarius",
      "transiting_house": 3,
      "natal_planet": "moon",
      "natal_sign": "aquarius",
      "natal_house": 3,
      "aspect": "conjunction",
      "orb": 2.8821,
      "score": 9.5961,
      "narrative": "In matters of communication, siblings, and everyday learning (house 3). Brings deep, often hidden transformation - the surfacing or dismantling of something that has outgrown its old form."
    }
  ],
  "celtic_cross": [
    {
      "position": "present",
      "card": "emperor",
      "reversed": true,
      "card_name": "The Emperor",
      "meaning": "Benevolence, compassion, credit; also confusion to enemies, obstruction, immaturity."
    }
  ],
  "guidance": "With Pluto as today's dominant influence: Today concentrates whatever you already bring to it - your current approach will be amplified, so make sure it's the one you want.\nYour Attitude card is The Magician: Skill, diplomacy, address, subtlety; self-confidence, will.\nThe spread's likely Outcome is Strength: Power, energy, action, courage, magnanimity; complete success and honours."
}
```

- `significant_transits` has `interp.top_item_count` entries (0-5, same
  ranking as `--format text`); `celtic_cross` always has exactly 10, in
  `CelticCrossPosition` enum order (same order as `deck-engine`'s own
  `spread.positions`).
- `orb`/`score` are `%.4f`, matching `deck-engine`'s own JSON precision
  for angles.
- `guidance` is always present and non-empty (unlike
  `significant_transits`, which can be `[]` on a genuinely quiet day) -
  see `guidance.c`'s no-aspects-at-all fallback in `CLAUDE.md`.
- With `--lang de`, every string value above except the slugs
  (`"level"`, `"transiting_planet"`, `"aspect"`, `"card"`, `"position"`,
  etc.) changes language; the slugs never do.
