Replay engine for GameChanger event streams. Parses the raw scoring data from GameChanger's play-by-play API and computes 40+ stats per player, plus youth-specific analytics. Built for youth baseball.
diamond-replay game.json
diamond-replay game.json --json
diamond-replay game.json --json --little-league
diamond-replay game.json --json --no-steal-home
Four TUI views: Box Score, Batting, Pitching, Little League. Press ? on any stat column for an interactive help card with formula, MLB benchmarks, youth context, and caveats. Enter to sort by selected column.
--little-league adds per-team youth stats: run sourcing, pace, baserunning chaos, free bases.
--no-steal-home replays the game with chaos scoring from 3B blocked. Runners stay at 3B but auto-score on any subsequent ball in play that doesn't end the inning, plus forced advances such as walks and HBP.
use diamond_replay::{replay_from_json, replay_from_json_with_options, ReplayOptions};
let result = replay_from_json(&event_json)?;
let simulated = replay_from_json_with_options(
&event_json,
ReplayOptions::no_steal_home(),
)?;
for (id, player) in &result.player_stats {
let b = &player.batting;
println!("{id}: {}/{} | {:.3} wOBA", b.hits, b.ab, b.woba.unwrap_or(0.0));
}The supported library surface is exposed from the crate root: replay functions, ReplayOptions, RuleSet, RawApiEvent, ReplayError, GameResult, and the result stat structs.
PA, AB, H, TB, XBH, AVG, OBP, SLG, OPS, ISO, BABIP, wOBA, K%, BB%, BB/K, GB%, FB%, LD%, HR/FB, RBI, R, SB, CS, SB%, GIDP, CI, QAB%, Competitive AB%, P/PA, Hard Hit%.
IP, BF, Pitches, ERA, FIP, WHIP, K/9, BB/9, H/9, HR/9, K%, BB%, K-BB%, SwStr%, CSW%, FPS%, CStr%, Foul%, BABIP, HR/FB, GB%, FB%, LD%, Game Score, Pitches/IP.
| Category | Stats |
|---|---|
| Run sourcing | Runs on BIP, passive runs, BIP run % |
| Pace | Pitches per BIP, median pitches between BIP |
| Baserunning | Steals of home, WP, PB, CS |
| Free bases | BB + HBP + WP + PB + SB, per inning |
| Pitching | Pitches, ball%, strike%, K/inn, BB/inn, BIP/inn |
| Defense | Opponent SB, free bases allowed per inning |
Linescores, transition gaps, dead time per inning, timestamps.
[dependencies]
diamond-replay = { git = "https://github.com/Jud/diamond-replay" }GameChanger game stream data: JSON arrays of scoring events from the GameChanger API. Each event has a sequence_number, an event_data JSON string containing the play details (pitches, BIP, base running, lineups), and optional created_at timestamps.
Events map 1:1 to scorer actions in the GameChanger app. They can be single plays or bundled transactions (e.g., a pitch + ball-in-play + base-running result in one atomic group). The engine handles undo/redo corrections, manual score overrides, dropped third strikes, catcher interference, and short lineups.
See testdata/ for 14 complete game files from real 10U and 13U games.
cargo test
100 tests: 64 unit (stat computation, stat help coverage, rule compiler, stream traversal, shadow state, lineup mutation handling), 34 integration/artifact tests (full-game linescores, accounting gates, LL balance invariants, undo/redo, simulation), and 2 doctests.
~6,200 lines of Rust, plus fixture-backed integration tests. Dependencies: serde, serde_json, thiserror, ratatui, crossterm.
src/
lib.rs public API and stable type re-exports
event.rs JSON parsing, typed event enums
undo.rs stack-based undo/redo resolution
rules/ rule-set event stream compilers
state.rs GameState, BaseState, PAContext
replay.rs state machine, event loop, LL stats
compute.rs pure stat formulas
score.rs run recording, force-advance, overrides
player.rs lineup tracking, stat attribution
stat_help.rs interactive stat help data (30 entries)
bin/diamond-replay TUI + JSON CLI
Requires tracking hardware: exit velocity, launch angle, barrel%, sprint speed, bat speed, Stuff+, xBA/xSLG/xwOBA, spin rate, pitch movement, OAA, catcher framing.
See docs/STATISTICS.md for full stat reference.
MIT