1 files changed, 56 insertions, 0 deletions
diff --git a/web/frontend/official-climb-profile-logic.ts b/web/frontend/official-climb-profile-logic.ts
new file mode 100644
index 0000000..1b2bc83
--- /dev/null
+++ b/web/frontend/official-climb-profile-logic.ts
@@ -0,0 +1,56 @@
+import type { ProfileBand, ProfilePoint } from "./types.js";
+
+export interface OfficialProfileSection {
+  startDistanceKm: number;
+  endDistanceKm: number;
+  startElevation: number;
+  endElevation: number;
+  slopePercent: number;
+  band: ProfileBand;
+}
+
+const clamp = (value: number, min: number, max: number) => Math.max(min, Math.min(max, value));
+const profileStepSizesM: number[] = [100, 200, 500, 1000];
+const displayStepForLength = (lengthM: number): number =>
+  profileStepSizesM.find((stepM) => Math.ceil(lengthM / stepM) <= 30) || profileStepSizesM[profileStepSizesM.length - 1];
+const profileBandForSlope = (slopePercent: number): ProfileBand => {
+  if (slopePercent < 0) return "downhill";
+  if (slopePercent < 3) return "0-3";
+  if (slopePercent < 6) return "3-6";
+  if (slopePercent < 9) return "6-9";
+  if (slopePercent < 12) return "9-12";
+  return "12-plus";
+};
+const officialProfileSections = (points: ProfilePoint[], startIndex: number, endIndex: number, stepM: number): OfficialProfileSection[] => {
+  const startDistanceM = points[startIndex].distanceKm * 1000;
+  const endDistanceM = points[endIndex].distanceKm * 1000;
+  const sections: OfficialProfileSection[] = [];
+  let pointIndex = startIndex;
+  const elevationAtDistance = (distanceM: number) => {
+    while (pointIndex < endIndex - 1 && points[pointIndex + 1].distanceKm * 1000 < distanceM) pointIndex++;
+    const nextIndex = Math.min(pointIndex + 1, endIndex);
+    const first = points[pointIndex];
+    const next = points[nextIndex];
+    const distanceSpan = next.distanceKm * 1000 - first.distanceKm * 1000;
+    if (distanceSpan <= 0) return first.elevationM;
+    const fraction = (distanceM - first.distanceKm * 1000) / distanceSpan;
+    return first.elevationM + clamp(fraction, 0, 1) * (next.elevationM - first.elevationM);
+  };
+  for (let sectionStartM = startDistanceM; sectionStartM < endDistanceM; sectionStartM += stepM) {
+    const sectionEndM = Math.min(sectionStartM + stepM, endDistanceM);
+    const startElevation = elevationAtDistance(sectionStartM);
+    const endElevation = elevationAtDistance(sectionEndM);
+    const slopePercent = ((endElevation - startElevation) / (sectionEndM - sectionStartM)) * 100;
+    sections.push({
+      startDistanceKm: sectionStartM / 1000,
+      endDistanceKm: sectionEndM / 1000,
+      startElevation,
+      endElevation,
+      slopePercent,
+      band: profileBandForSlope(slopePercent),
+    });
+  }
+  return sections;
+};
+
+export { displayStepForLength, profileBandForSlope, officialProfileSections };