LEDMatrix/docs/SPORTS_UNIFICATION.md

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: only when its manifest floors ledmatrix_min_version at the first core release shipping the module (recorded in CHANGELOG.md).

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

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:

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. A plugin needing an ordering core does not ship calls register_rotation_strategy instead of core growing a branch.

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.

Phases

Phase	Scope	Risk control
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 must stay green; no behavior change intended
B2 ✅	CelebrationMixin + rotation strategies as opt-in capabilities	Plugins that don't opt in have zero new code in their MRO; strategies checked against verbatim plugin transcriptions
B3	Upstream ScrollDisplay as src/common/sports_scroll.py, reading global_config['target_fps'] natively	Plugin copies remain until sunset
B4	Bump to 3.2.0, record modules in CHANGELOG, migrate ledmatrix_min → ledmatrix_min_version	Gives plugins a version to floor on
B5	Pilot one plugin per lineage (hockey, soccer, football) on guarded core imports; then the remaining six; then delete bundled copies	Pilot soaks before rollout; harness + golden suites gate each

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.