chore: initial Observable workspace with technical README

docs/data/ufo-ca-sightings.json.js

@@ -0,0 +1,83 @@
+const candidates = [
+  "https://raw.githubusercontent.com/richaude/blue-book/master/scrubbed.csv",
+  "https://raw.githubusercontent.com/alecfirrincieli/UFO-sightings/main/ufo-sightings.csv",
+];
+
+let csvText = null;
+for (const url of candidates) {
+  try {
+    const response = await fetch(url);
+    if (!response.ok) continue;
+    const text = await response.text();
+    if (text && text.includes("datetime,city,state")) {
+      csvText = text;
+      break;
+    }
+  } catch {}
+}
+
+if (!csvText) {
+  throw new Error("Unable to fetch UFO sightings dataset from public mirrors.");
+}
+
+const { csvParse } = await import("d3-dsv");
+const rows = csvParse(csvText);
+
+const normalizeKey = (value) =>
+  String(value ?? "")
+    .trim()
+    .toLowerCase();
+
+function readField(row, key) {
+  const target = normalizeKey(key);
+  for (const [field, value] of Object.entries(row)) {
+    if (normalizeKey(field) === target) return value;
+  }
+  return undefined;
+}
+
+function parseNumber(value) {
+  const parsed = Number(value);
+  return Number.isFinite(parsed) ? parsed : null;
+}
+
+const ufo = rows
+  .map((row, index) => {
+    const state = String(readField(row, "state") ?? "")
+      .trim()
+      .toLowerCase();
+    const country = String(readField(row, "country") ?? "")
+      .trim()
+      .toLowerCase();
+    const latitude = parseNumber(readField(row, "latitude"));
+    const longitude = parseNumber(readField(row, "longitude"));
+
+    if (state !== "ca" || country !== "us") return null;
+    if (latitude === null || longitude === null) return null;
+
+    const inCaliforniaBounds =
+      latitude >= 32 &&
+      latitude <= 42.5 &&
+      longitude >= -125 &&
+      longitude <= -114;
+
+    if (!inCaliforniaBounds) return null;
+
+    const durationSeconds =
+      parseNumber(readField(row, "duration (seconds)")) ?? 0;
+
+    return {
+      id: `ufo/${index}`,
+      datetime: readField(row, "datetime") ?? null,
+      city: readField(row, "city") ?? "Unknown",
+      state,
+      shape: String(readField(row, "shape") ?? "unknown").toLowerCase(),
+      durationSeconds,
+      comments: readField(row, "comments") ?? "",
+      latitude,
+      longitude,
+    };
+  })
+  .filter(Boolean);
+
+process.stdout.write(JSON.stringify(ufo));