Files
ew_author/src/router/custom_song/chart.rs
Ethan O'Brien 6b465eca8e Minor changes
2026-07-03 00:40:06 -05:00

267 lines
10 KiB
Rust

use jzon::{object, JsonValue};
// Transcodes a SIF1/NPPS4 beatmap (array of {timing_sec, effect, effect_value, position})
// into the SIF2 chart JSON the client deserializes into NoteData.
//
// Mapping rules:
// - line = position - 1 (both are right-to-left)
// - effect 1 (and 2, the "parallel" marker) -> type 1 (tap)
// - effect 3 (hold) -> head note (type 1) at timing_sec plus a SYNTHESIZED tail note
// (type 1, same line) at timing_sec + effect_value, linked through parent/child ids
// - effect 4 (star/token) -> type 3
// - effect 11/12/13 (swing) and anything unknown -> plain type 1 tap for v1.
// Slider chains are a later feature.
// - notes_attribute / notes_level are dropped (SIF2 has no per-note attribute)
// - ids are sequential from 1 in time order. num is the spawn group: the dummy
// header occupies 100, real groups count up from 101, and notes that hit
// simultaneously (equal timing_sec, which covers SIF1 effect 2 pairs) share one num.
// - notes[0] is ALWAYS the dummy header (id 0, num 100, type 0) - the client
// deserializes it verbatim.
// - max_combo_count = all real notes EXCEPT hold heads whose tail is on the same
// line (the game counts a same-lane hold as one combo for the chain)
struct WorkNote {
time: f64,
line: i64,
kind: i64,
// Index into the work list of the hold head this tail belongs to
head: Option<usize>
}
fn parse_sif_note(data: &JsonValue, index: usize) -> Result<(f64, i64, f64, i64), String> {
let timing = data["timing_sec"].as_f64().ok_or(format!("Note {}: missing timing_sec", index))?;
let effect = data["effect"].as_i64().ok_or(format!("Note {}: missing effect", index))?;
let effect_value = data["effect_value"].as_f64().unwrap_or(0.0);
let position = data["position"].as_i64().ok_or(format!("Note {}: missing position", index))?;
if !(1..=9).contains(&position) {
return Err(format!("Note {}: position {} is outside 1-9", index, position));
}
if timing < 0.0 {
return Err(format!("Note {}: negative timing_sec {}", index, timing));
}
if effect == 3 && effect_value <= 0.0 {
return Err(format!("Note {}: hold with effect_value {} (must be > 0)", index, effect_value));
}
Ok((timing, effect, effect_value, position))
}
// Returns the chart JSON and its max_combo_count (== the difficulty's full_combo)
pub fn transcode(beatmap: &JsonValue) -> Result<(JsonValue, i64), String> {
if !beatmap.is_array() || beatmap.is_empty() {
return Err(String::from("Chart is not a JSON array of notes"));
}
let mut work: Vec<WorkNote> = Vec::new();
for (i, data) in beatmap.members().enumerate() {
let (timing, effect, effect_value, position) = parse_sif_note(data, i)?;
for other in beatmap.members().take(i) {
if other["timing_sec"].as_f64() == Some(timing) && other["position"].as_i64() == Some(position) && other["effect"].as_i64() != Some(effect) {
return Err(format!("Note {}: duplicate timing {} on position {} with a different effect", i, timing, position));
}
}
let head = work.len();
work.push(WorkNote {
time: timing,
line: position - 1,
kind: if effect == 4 { 3 } else { 1 },
head: None
});
if effect == 3 {
work.push(WorkNote {
time: timing + effect_value,
line: position - 1,
kind: 1,
head: Some(head)
});
}
}
// Sequential ids in time order. Stable sort keeps input order on ties
let mut order: Vec<usize> = (0..work.len()).collect();
order.sort_by(|a, b| work[*a].time.partial_cmp(&work[*b].time).unwrap());
let mut ids = vec![0i64; work.len()];
let mut nums = vec![0i64; work.len()];
let mut num = 100;
let mut last_time = f64::NEG_INFINITY;
for (i, index) in order.iter().enumerate() {
ids[*index] = (i + 1) as i64;
// Simultaneous notes share a spawn group
if work[*index].time != last_time {
num += 1;
last_time = work[*index].time;
}
nums[*index] = num;
}
let mut tail_of = vec![0usize; work.len()];
for (i, note) in work.iter().enumerate() {
if let Some(head) = note.head {
tail_of[head] = i;
}
}
let mut notes = jzon::array![{
"id": 0, "num": 100, "line": 0, "time": 0.0, "type": 0,
"parent_id": 0, "child_id": 0, "child_num": 0, "child_line": 0,
"force_sync_group_id": 0
}];
let mut max_combo_count = 0;
for index in order.iter() {
let note = &work[*index];
let tail = tail_of[*index];
let is_head = tail != 0;
// Same-lane hold heads don't count toward the combo, their tail does
if !(is_head && work[tail].line == note.line) {
max_combo_count += 1;
}
notes.push(object!{
"id": ids[*index],
"num": nums[*index],
"line": note.line,
"time": note.time,
"type": note.kind,
"parent_id": if let Some(head) = note.head { ids[head] } else { 0 },
"child_id": if is_head { ids[tail] } else { 0 },
"child_num": if is_head { nums[tail] } else { 0 },
"child_line": if is_head { work[tail].line } else { 0 },
"force_sync_group_id": 0
}).unwrap();
}
Ok((object!{
"max_lane": 9,
"sound_name": "",
"max_combo_count": max_combo_count,
"notes": notes
}, max_combo_count))
}
#[cfg(test)]
mod tests {
use super::*;
fn sif_note(timing_sec: f64, position: i64, effect: i64, effect_value: f64) -> JsonValue {
object!{
"timing_sec": timing_sec,
"notes_attribute": 1,
"notes_level": 1,
"effect": effect,
"effect_value": effect_value,
"position": position
}
}
#[test]
fn plain_taps() {
let beatmap = jzon::array![
sif_note(1.0, 1, 1, 2.0),
sif_note(2.0, 5, 1, 2.0),
sif_note(3.0, 9, 1, 2.0)
];
let (chart, combo) = transcode(&beatmap).unwrap();
assert_eq!(combo, 3);
assert_eq!(chart["max_combo_count"], 3);
assert_eq!(chart["max_lane"], 9);
assert_eq!(chart["notes"].len(), 4);
// Dummy header is verbatim
assert_eq!(chart["notes"][0]["id"], 0);
assert_eq!(chart["notes"][0]["num"], 100);
assert_eq!(chart["notes"][0]["type"], 0);
// Real notes: sequential ids, monotonic nums, right-to-left lines
assert_eq!(chart["notes"][1]["id"], 1);
assert_eq!(chart["notes"][1]["num"], 101);
assert_eq!(chart["notes"][1]["line"], 0);
assert_eq!(chart["notes"][1]["type"], 1);
assert_eq!(chart["notes"][2]["num"], 102);
assert_eq!(chart["notes"][2]["line"], 4);
assert_eq!(chart["notes"][3]["id"], 3);
assert_eq!(chart["notes"][3]["num"], 103);
assert_eq!(chart["notes"][3]["line"], 8);
}
#[test]
fn hold_head_and_tail() {
let beatmap = jzon::array![
sif_note(1.0, 3, 3, 2.5)
];
let (chart, combo) = transcode(&beatmap).unwrap();
// The synthesized same-lane tail counts, the head does not
assert_eq!(combo, 1);
assert_eq!(chart["notes"].len(), 3);
let head = &chart["notes"][1];
let tail = &chart["notes"][2];
assert_eq!(head["id"], 1);
assert_eq!(head["child_id"], 2);
assert_eq!(head["child_num"], tail["num"].clone());
assert_eq!(head["child_line"], 2);
assert_eq!(head["parent_id"], 0);
assert_eq!(tail["id"], 2);
assert_eq!(tail["parent_id"], 1);
assert_eq!(tail["child_id"], 0);
assert_eq!(tail["line"], 2);
assert_eq!(tail["time"].as_f64().unwrap(), 3.5);
}
#[test]
fn parallel_pair() {
let beatmap = jzon::array![
sif_note(1.0, 2, 2, 2.0),
sif_note(1.0, 8, 2, 2.0)
];
let (chart, combo) = transcode(&beatmap).unwrap();
// Simultaneous notes share a spawn group and both count
assert_eq!(combo, 2);
assert_eq!(chart["notes"][1]["num"], chart["notes"][2]["num"].clone());
assert_eq!(chart["notes"][1]["type"], 1);
assert_eq!(chart["notes"][2]["type"], 1);
}
#[test]
fn mixed() {
let beatmap = jzon::array![
sif_note(1.0, 5, 1, 2.0), // tap
sif_note(2.0, 3, 3, 1.5), // hold: head at 2.0, tail at 3.5
sif_note(2.5, 7, 4, 0.0), // star
sif_note(3.5, 1, 2, 2.0), // parallel with the hold tail
sif_note(4.0, 9, 11, 0.0) // swing -> plain tap for v1
];
let (chart, combo) = transcode(&beatmap).unwrap();
// 6 real notes, minus the same-lane hold head
assert_eq!(combo, 5);
assert_eq!(chart["notes"].len(), 7);
// Time order: tap(1.0), head(2.0), star(2.5), tail(3.5), parallel(3.5), swing(4.0)
assert_eq!(chart["notes"][2]["child_id"], 4);
assert_eq!(chart["notes"][3]["type"], 3);
assert_eq!(chart["notes"][4]["parent_id"], 2);
// The tail and the parallel tap at 3.5 share a spawn group
assert_eq!(chart["notes"][4]["num"], chart["notes"][5]["num"].clone());
assert_eq!(chart["notes"][6]["type"], 1);
// Ids stay sequential in time order
for (i, data) in chart["notes"].members().enumerate() {
assert_eq!(data["id"], i);
}
}
#[test]
fn rejects_bad_charts() {
assert!(transcode(&jzon::array![sif_note(1.0, 0, 1, 2.0)]).is_err());
assert!(transcode(&jzon::array![sif_note(1.0, 10, 1, 2.0)]).is_err());
assert!(transcode(&jzon::array![sif_note(-1.0, 5, 1, 2.0)]).is_err());
assert!(transcode(&jzon::array![sif_note(1.0, 5, 3, 0.0)]).is_err());
assert!(transcode(&jzon::array![sif_note(1.0, 5, 1, 2.0), sif_note(1.0, 5, 3, 2.0)]).is_err());
assert!(transcode(&jzon::object!{}).is_err());
}
}