# Sports Code Unification — Architecture

How the nine sports scoreboard plugins converge onto shared core code **without**
becoming nine clients of a god class.

## The problem

Nine plugins (`afl`, `baseball`, `basketball`, `football`, `hockey`, `lacrosse`,
`nrl`, `soccer`, `ufc`) each ship a ~3,000-line `sports.py` descended from this
repo's `src/base_classes/sports.py`. They have drifted into three lineages, and
only 28 of the 66 methods appearing across them are present in all nine. One
logical fix (the UTC start-time bug) cost 75 files.

Merging everything into one base class would fix the duplication and create a
worse problem: a single 2,500-line class that all nine plugins inherit, where any
change has a nine-plugin blast radius and per-sport behavior survives only as
`if self.sport == "hockey"` branches.

## Three properties, three mechanisms

These are independent concerns. Conflating them is what produces god classes.

### Upgradability — a plugin keeps working across core versions

| Rule | Mechanism |
|---|---|
| Plugin loads on a core that predates a module | Guarded import with a bundled fallback (`try: from src.X import Y / except ModuleNotFoundError: from y import Y`) |
| Plugin loads on a core that predates a *method* | Capability probing — `hasattr(SportsCore, "_detect_stale_games")` — never a version comparison. The loader's compat check is advisory-only (it logs and continues), so probing is the real protection. |
| Core changes never break a plugin's rendering | The **view-model contract**: `_extract_game_details_common` returns a dict whose `GUARANTEED_KEYS` are frozen by `test/test_skin_system.py::TestViewModelContract`. Keys may be added, never renamed or removed. |
| A plugin can drop its bundled copy safely | The **sunset rule**: its manifest must floor `ledmatrix_min_version` at the first core release shipping the module (recorded in `CHANGELOG.md`) — *necessary but not sufficient*. Nothing enforces that floor today, so the copy also waits for the B6 gate below. |

The core API is **additive-only**. A method the plugins call is never removed or
given a new required parameter; new behavior arrives as new methods with
defaults, or as capabilities they opt into.

### Reusability — write once, nine plugins benefit

Only code that is **identical in intent across all nine** moves into the base
class. That set is small and knowable — it is exactly the methods present in every
copy today (phase B1 below). Everything else stays where it is until it earns
promotion.

### Modularity — a change to one feature cannot reach a plugin that doesn't use it

This is the property the naive merge destroys, and it is enforced structurally:

1. **Capabilities are separate modules composed by inheritance, not config
   branches inside the base class.** Hockey has no celebrations, so
   `HockeyLive` does not inherit `CelebrationMixin` — the celebration code is not
   merely disabled for hockey, it is *not in hockey's MRO at all*. No shared
   state, no dead branches, no risk. Contrast with
   `if self.celebrations_enabled:` inside `SportsLive`, where a bug in
   celebration code can still crash a plugin that never wanted the feature.

2. **Variant behavior is a strategy object chosen by name, not a branch.**
   Live rotation exists in three dialects across the lineages; core ships all
   three behind `rotation_strategy: "swrr" | "weighted" | "simple"` and a plugin
   may register its own. Core never learns sport names.

3. **Sport-specific behavior is a documented override point.** The base class
   declares the seam; the plugin fills it. Basketball's tournament-round parsing
   and baseball's BDF sizing stay in their plugins forever — they are not
   candidates for promotion, and core must never grow a branch for them.

4. **Files bound the blast radius.** Capabilities live in their own modules so a
   diff shows at a glance which plugins a change can reach.

## Layering

```
src/base_classes/sports/
  __init__.py            re-exports the public API (import path unchanged)
  core.py                SportsCore — fetch, cache, config, logos, fonts, odds,
                         view-model extraction, the skin seam
  modes.py               SportsUpcoming / SportsRecent / SportsLive
  capabilities/
    celebrations.py      CelebrationMixin        (opt-in: 4 of 9 plugins)
    rotation.py          RotationStrategy + registry

src/common/
  sports_scroll.py       SportsScrollDisplay / …Manager — scroll orchestration
                         (content building stays in the plugins)
```

`from src.base_classes.sports import SportsCore` keeps working — the package
`__init__` re-exports, so the conversion is invisible to every existing importer.

## Override points (the plugin-facing seam)

The base class calls these; plugins implement or override them. This table is the
contract — additions require a default implementation, removals require a
deprecation cycle.

| Hook | Purpose | Default |
|---|---|---|
| `_fetch_data()` | Sport's schedule source | abstract |
| `_extract_game_details(event)` | Sport-specific view-model fields on top of the common ones | delegates to `_extract_game_details_common` |
| `_draw_scorebug_layout(game, force_clear)` | Sport's card rendering | base layout |
| `_custom_scorebug_layout(game, draw)` | Per-sport overlay on the base layout | no-op |
| `render_skin_card(game, size)` | Skin-system entry point | built-in fallback |
| `score_phrase(points, team_abbr)` | Celebration wording (`"GOOOOAAALLL!"` vs `"TOUCHDOWN!"`). `points` is the score delta, which sports with variable-value scores use to name the play | `"<abbr> SCORES!"` — only consulted when `CelebrationMixin` is present |
| `win_phrase(team_abbr)` | Win-celebration wording | `"<abbr> WINS!"` — mixin only |
| `_favorite_key(game, side)` | Which view-model field identifies a team for favorites matching | `game["<side>_abbr"]` |
| `_config_schema_path()` | Plugin's `config_schema.json` — returning it routes `_get_layout_offset` through the `src.element_style` resolver (and gives it the defaults to compare against) | `None`, i.e. the classic inline `customization.layout` read |
| `_font_root()` | Directory to resolve `assets/fonts` against | core install root |

Two class attributes serve the same purpose for values that are per-sport
constants rather than behavior:

| Attribute | Meaning | Default |
|---|---|---|
| `FINAL_PERIOD` | Period at/after which a zero clock can mean "over" | `4` (hockey overrides to `3`) |
| `CLOCK_COUNTS_DOWN` | Whether `0:00` means "expired" | `True` (soccer/afl/nrl override to `False` — their clocks count up, so `0:00` is kickoff) |
| `COALESCE_SCORING_SEQUENCE` | Fold score increments arriving during an active celebration into that one celebration | `False` (football overrides to `True` — a touchdown lands as +6, then +1 for the extra point) |

### Why these are seams and not branches

`_favorite_key` exists because NRL abbreviations are **not unique** — "NEW" is both
Newcastle Knights and New Zealand Warriors, "CAN" both Canberra and Canterbury —
so NRL matches favorites on team ID. Flattening every plugin to abbreviations
would silently select the wrong club for NRL users. The base declares the seam,
NRL fills it, and core never learns the string `"nrl"`.

`CLOCK_COUNTS_DOWN` exists for the same reason in the opposite direction: a
soccer clock reading `0:00` means the match has not kicked off, so running the
clock-expiry branch there would evict live games.

`COALESCE_SCORING_SEQUENCE` is the third of the same kind. In football one
scoring play arrives as two score updates, so the follow-up must be folded into
the first celebration; in soccer two increments a few seconds apart are two real
goals, and folding them would swallow one. Neither default is "right" — which is
precisely why it is a declared per-sport constant rather than a hidden
assumption baked into the shared body.

## Capabilities

```
capabilities/
  celebrations.py   CelebrationMixin        opt-in: afl, nrl, soccer, football
  rotation.py       RotationStrategy + registry
```

**`CelebrationMixin`** merges the two dialects the lineages grew
(`_check_for_goal`/`celebrate_opponent_goals` vs
`_check_for_score`/`celebrate_opponent_scores`). Their bodies were identical
apart from three things, each now a seam: wording (`score_phrase`), follow-up
suppression (`COALESCE_SCORING_SEQUENCE`), and team identity (`_favorite_key`,
so NRL matches on id). Both config spellings are read, so a plugin adopting the
mixin keeps working with the keys already in its published schema.

Mix it in **before** the mode class — `class SoccerLive(CelebrationMixin,
SportsLive)` — so the celebration `display()` runs first and falls through to
the scorebug via `super()`.

**Rotation strategies.** The three "dialects" turned out to be one algorithm
(Smooth Weighted Round-Robin) in two shapes: an incremental picker holding state
across calls (afl/nrl/soccer) and a precomputed per-cycle list
(football/baseball/basketball, and hockey with a different loop shape). They
agree within a cycle and differ only at the boundary — the incremental form has
no restart seam — so core ships both rather than declaring a winner:

```python
self.rotation = get_rotation_strategy("swrr", weight_for=self._live_weight)
```

`weight_for` is supplied by the host, so the *favorites* policy stays with the
plugin and `rotation.py` never learns what a favorite is. An unknown strategy
name degrades to `simple` rather than raising: the name comes from user config,
and a typo should cost the boost, not the scoreboard. When a plugin needs an
ordering that core does not ship, it calls `register_rotation_strategy` to add
its own — rather than core growing a branch for it.

`test_sports_capabilities.py` checks each strategy against a **verbatim
transcription** of the plugin code it replaces, over every live-game shape up to
four games. That differential is what B5 deletes the bundled copies on the
strength of.

## Scroll display — where the promotion line falls

`src/common/sports_scroll.py` is deliberately *not* a superset of the ten
`scroll_display.py` copies. A method-level comparison of the eight that share a
shape (f1 and ufc are genuine forks) found a sharp split:

| Layer | Evidence | Outcome |
|---|---|---|
| Orchestration — `get_all_vegas_content_items`, `clear_all`, `get_scroll_info`, `get_dynamic_duration`, `is_complete`, `display_frame` | identical to 96–100% similar across all eight | **promoted** |
| Settings — `_get_scroll_settings` | one algorithm; the copies differ *only* in which league keys they walk | **promoted**, with the ladder as data (`SCROLL_LEAGUE_KEYS`) |
| Content — `prepare_scroll_content`, `_load_separator_icons` | 8 distinct bodies across 8 plugins (145 lines, 53% similar at worst); icons 6% | **override point, permanently** |

Same name, different job: `prepare_scroll_content` draws *this sport's* game
card. Merging the eight bodies would be the exact mistake the promotion rule
exists to prevent, so the base class raises `NotImplementedError` rather than
rendering something plausible — a base that rendered *something* would let a
plugin ship a silently blank scroll.

The one behavior the upstreamed version adds is native
`global_config['target_fps']` support. The bundled copies hardcode ~100 FPS via
`scroll_delay = 0.01` and never consult the global smooth-scrolling target;
Part A threaded it through each copy by hand, and this makes that threading
legacy compatibility rather than the mechanism.

## Phases

B0–B3 are merged and shipping in core 3.2.0. Everything that remains is
**rollout**, and it splits into three phases with very different risk profiles.
The original plan folded the last two together; they are separated here because
one of them is safe by construction and the other is not.

| Phase | Scope | Status | Gate |
|---|---|---|---|
| **B0** | Characterization tests, CI unit job, `element_style`, font cwd fix, CHANGELOG discipline | ✅ | — |
| **B1** | Promote the nine universal methods; convert `sports.py` → package | ✅ | Characterization suite green; no behavior change intended |
| **B2** | `CelebrationMixin` + rotation strategies as opt-in capabilities | ✅ | Non-adopters have zero new code in their MRO; strategies checked against verbatim plugin transcriptions |
| **B3** | Upstream the scroll **orchestration** layer as `src/common/sports_scroll.py`, reading `global_config['target_fps']` natively | ✅ | Content building stays per-sport |
| **B4** | Ship 3.2.0 *and* make version reporting trustworthy | ⏳ **next** | Tag, release, and `src.__version__` agree; compatibility gate merged |
| **B5** | Adoption — guarded core imports: three pilots, then the remaining six. **Bundled copies stay.** | after B4 | Per plugin: harness + goldens byte-identical, then a device soak |
| **B6** | Sunset — delete the bundled copies | **blocked** | B4's gate shipped *and* in users' hands (see below) |

### B4 — what "ship 3.2.0" actually requires

Cutting the tag is the small part. The version *number* has to become something
a floor can be trusted against, and today it is not:

- **The tag and `src.__version__` have never agreed.** `v3.1.0` was tagged
  2026-05-31; `__version__` only became `"3.1.0"` on 2026-07-12 (`7f7f0d64`).
  The v3.1.0 release therefore reports `__version__ = "1.0.0"`.
- **Which silences the compatibility warning entirely for that population.**
  `PluginLoader._warn_if_incompatible` skips the check when the parsed core
  version is below `(2, 0, 0)` — an anti-spam guard that, given the above,
  matches exactly the users most likely to be behind.
- **Nothing enforces a floor anyway.** The check is advisory (it logs and
  continues), and neither `StoreManager.install_plugin` nor
  `StoreManager.update_plugin` compares the core version at all — `update_plugin`
  compares the plugin's manifest version against the registry's
  `latest_version` and nothing else.

So B4 is: tag and release 3.2.0; make the tag, the release, and `__version__`
agree, and keep them agreeing; reconsider the `< 2.0.0` skip; migrate manifests
from `ledmatrix_min` to `ledmatrix_min_version`; and add the install/update
compatibility gate that B6 depends on.

### B5 — adoption is safe by construction

A plugin adopting core imports keeps its bundled copy and reaches it through the
guarded import (see the Upgradability table above). On a core that ships the
module the plugin uses core code; on one that doesn't it falls back and behaves
exactly as it does today. There is no version of this step that breaks a user,
which is why it does not wait for B6's gate.

The hockey scroll-display pilot is **already validated**: adopted against a core
carrying 3.2.0, `scroll_display.py` went from 691 to 289 lines and all 16 harness
renders (8 sizes × 2 screens) came out byte-for-byte identical to the
pre-adoption run. That byte-comparison is the acceptance gate for every
adoption. The recipe and its two gotchas are in the plugins repo's
`docs/plugin-development/08-shared-sports-code.md`.

### B6 — why the sunset needs more than a version floor

Deleting a bundled copy removes the fallback, so the guarded import becomes a
hard dependency. On a core without the module the plugin raises
`ModuleNotFoundError` at load; `PluginManager.load_plugin` catches it, records
`PluginState.ERROR`, logs one line, and continues. Nothing crashes — the user
simply loses that scoreboard, with no visible explanation.

Verified against a `v3.1.0` worktree: `src/common/sports_scroll.py`,
`src/element_style.py` and the `src/base_classes/sports/` package are all absent
there, and the import fails with `exc.name == 'src.common.sports_scroll'`. Guard
sets must name that exact dotted path — `{"src"}` alone does not match it.

Combined with the B4 findings, a plugin that deletes its copy today reaches an
un-updated user through a normal store update, fails to load, and warns nobody.
**B6 therefore waits for B4's compatibility gate to have shipped and to have
been in users' hands long enough that the population running a core without it
is small.** The bundled copies cost disk space; deleting them early costs
scoreboards, silently. That trade is not close.

Before the first sunset, add a **compatibility regression test**: load each
adopted plugin with its bundled copy removed against a pinned old-core worktree
and assert it fails loudly and specifically, then against current core and assert
it works. That test is what turns "we think this is safe" into something CI
re-checks on every change.

## What's next

In order. Each step is independently useful and independently revertible.

1. **Tag and publish v3.2.0.** The code is already on `main` (`21825cbf`).
   Nothing else blocks this, and it is what makes `ledmatrix_min_version:
   "3.2.0"` refer to something real.
2. **Make the version number honest.** Have the release process assert that the
   tag, the GitHub release, and `src.__version__` agree — a check in CI is
   cheaper than the confusion of the last two releases. Then revisit the
   `< 2.0.0` skip in `_warn_if_incompatible`, which currently silences the
   warning for the users who most need it.
3. **Add the compatibility gate** to `StoreManager.install_plugin` and
   `.update_plugin`: refuse a plugin whose declared floor exceeds
   `src.__version__`, and surface the reason in the store UI rather than only
   the log. This is the single change that turns the floor from documentation
   into a guarantee, and B6 depends on it.
4. **Migrate the manifests** to `ledmatrix_min_version`. Currently 28 plugins
   spell it both ways across their `versions[]` entries, 12 use only the old
   spelling, and 2 only the new. Scope the sweep to the nine sports plugins if a
   42-plugin version-bump wave isn't worth it.
5. **Run B5 adoption** — hockey, soccer, football, then the remaining six.
   Bundled copies stay. Byte-identical harness output per plugin, then a soak.
6. **Only then plan B6**, with the compatibility regression test described above
   in CI first.

## How to keep this project healthy

Lessons this migration paid for, worth applying beyond it:

- **A version number is a promise; keep it in one place.** Three different
  answers to "what version am I on" (tag, release, `__version__`) is what made
  the floor untrustworthy. Assert their agreement mechanically.
- **Advisory checks protect nobody.** If a rule matters, enforce it where the
  action happens — the install path, not a log line the user will never read.
  If it doesn't matter enough to enforce, don't write the rule.
- **Prefer failures that are loud and early.** A plugin that dies at load with
  one journal line is indistinguishable, to a user, from a plugin that was never
  installed. Surface plugin health in the UI.
- **Keep the two repos' rules in sync deliberately.** The sunset rule lives in
  both this file and the plugins repo's
  `docs/plugin-development/08-shared-sports-code.md`. When one changes, change
  the other in the same PR — drift between them is how a contributor ends up
  following a rule that was superseded.
- **Measure before and after, on real hardware.** Byte-identical harness renders
  and a device soak caught what unit tests could not. Reserve "it should be
  fine" for things you have actually looked at.

## Rules for contributors

- **Promote on evidence, not intuition.** A method moves to core when every copy
  has it and they agree on intent. Otherwise it stays in the plugins.
- **Never add a sport name to core.** If core needs to know which sport it is,
  the design is wrong — add an override point instead.
- **A capability that is not opted into must not execute.** If you find yourself
  writing `if self.<capability>_enabled` inside a base class, it belongs in a
  mixin.
- **Touch the view-model keys only additively.** Published skins depend on them.
- **Every promotion lands with the characterization suite green**, and every
  pilot adoption lands with that plugin's harness and golden suites green.