Henry Hub Forward Curve

[{"_1":2,"_3":-5,"_4":-5},"loaderData",{"_5":6,"_7":8,"_9":10},"actionData","errors","root",{"_153":154,"_155":156},"routes/_app.x.$handle.$name",{"_11":12,"_13":14,"_15":-7,"_18":19,"_17":-7,"_116":-5,"_20":117,"_22":118,"_119":120,"_121":122,"_25":123,"_24":-5,"_124":-5,"_125":-5,"_126":53,"_127":128,"_129":53,"_130":-5,"_131":-5,"_132":133},"routes/_app.x.$handle.$name.code.$",{"_11":12,"_13":14,"_15":16,"_17":-7,"_18":19,"_20":21,"_22":23,"_24":-7,"_25":26,"_27":-5,"_28":-5,"_29":-5,"_30":-5,"_31":-5},"handle","infoseg","name","GasWatch","branchName","main","version","path","","project",{"_33":61,"_13":14,"_45":62,"_63":-5,"_64":53,"_65":66,"_67":66,"_68":19,"_69":-5,"_70":71,"_72":-5,"_73":53,"_74":-5,"_75":-5,"_76":77,"_78":79,"_80":-5,"_81":-5,"_82":-5,"_83":-5,"_84":85,"_86":85,"_87":88,"_89":88,"_90":88,"_91":85,"_92":85,"_93":94,"_95":96,"_97":98,"_99":53},"tree",[56],"file","contents",[32],"upstream","pull","ahead","behind","envVars",{"_33":34,"_13":35,"_36":37,"_38":-5,"_39":40,"_41":42,"_43":44,"_45":46,"_17":47,"_48":49,"_50":51,"_52":53,"_54":-5,"_18":55},"id","f19f6bda-73a0-49c5-9ba2-244b63f0bec6","main.ts","fileId","04de85c2-9d9e-11f1-b561-1607ee4eb77e","parentId","branchId","4b4dcd01-dbf0-4c34-ad99-18aeb338c3f8","branchVersion",9,"latest",true,"createdAt",["D",1787348148080],8,"fileType","interval","content","/**\n * SEG Daily Henry Hub Forward Curve Report\n * -----------------------------------------\n * Pulls the 48-month NYMEX Henry Hub (NG) natural gas forward curve and\n * emails a formatted report every weekday at 8:30 AM Eastern.\n *\n * Platform: Val Town (Deno). Cron: \"30 12,13 * * *\" (UTC)\n * The double UTC hour + the isReportTime() guard below makes the job\n * fire at 8:30 AM Eastern year-round, through both EDT and EST.\n *\n * Data source: Yahoo Finance chart API (free, no key, no login).\n * Symbol format: NG{monthCode}{YY}.NYM e.g. NGV26.NYM = Oct 2026\n */\n\nimport { email } from \"https://esm.town/v/std/email\";\nimport { blob } from \"https://esm.town/v/std/blob\";\nimport * as XLSX from \"https://esm.sh/xlsx@0.18.5\";\n\n// ---------------------------------------------------------------- constants\n\nconst MONTH_CODES = [\n \"F\",\n \"G\",\n \"H\",\n \"J\",\n \"K\",\n \"M\",\n \"N\",\n \"Q\",\n \"U\",\n \"V\",\n \"X\",\n \"Z\",\n]; // Jan..Dec\nconst MONTH_NAMES = [\n \"January\",\n \"February\",\n \"March\",\n \"April\",\n \"May\",\n \"June\",\n \"July\",\n \"August\",\n \"September\",\n \"October\",\n \"November\",\n \"December\",\n];\nconst MONTH_ABBR = [\n \"Jan\",\n \"Feb\",\n \"Mar\",\n \"Apr\",\n \"May\",\n \"Jun\",\n \"Jul\",\n \"Aug\",\n \"Sep\",\n \"Oct\",\n \"Nov\",\n \"Dec\",\n];\n\nconst CURVE_LENGTH = 48; // months of forward curve to report\n\n/**\n * How many past weeks to render as tabs in the attached workbook, newest first.\n * Every snapshot is kept in blob storage forever regardless — raising this\n * number pulls older weeks back into the file, it does not resurrect lost data.\n * 13 weeks is one quarter; much past 26 and the tab strip gets unwieldy.\n */\nconst HISTORY_WEEKS = 13;\nconst BLOB_PREFIX = \"gascurve/\";\nconst RECIPIENTS: string[] = []; // leave empty = send to your own Val Town account email\n\n// SEG palette\nconst C = {\n navy: \"#12395F\",\n blue: \"#1B4B8F\",\n accent: \"#E8F1FA\",\n rule: \"#C9DCF0\",\n ink: \"#1F2933\",\n muted: \"#6B7A8D\",\n up: \"#0F7B4F\",\n down: \"#B3261E\",\n};\n\n// ------------------------------------------------------------ time handling\n\n/** Current wall-clock parts in America/New_York. */\nfunction easternNow(): {\n y: number;\n m: number;\n d: number;\n hour: number;\n minute: number;\n weekday: string;\n} {\n const fmt = new Intl.DateTimeFormat(\"en-US\", {\n timeZone: \"America/New_York\",\n year: \"numeric\",\n month: \"numeric\",\n day: \"numeric\",\n hour: \"numeric\",\n minute: \"numeric\",\n weekday: \"short\",\n hour12: false,\n });\n const p: Record = {};\n for (const part of fmt.formatToParts(new Date())) p[part.type] = part.value;\n return {\n y: +p.year,\n m: +p.month,\n d: +p.day,\n hour: +p.hour % 24,\n minute: +p.minute,\n weekday: p.weekday,\n };\n}\n\n/**\n * Eastern hours in which a report may be sent. The cron is doubled in UTC so\n * one firing always lands here regardless of daylight saving; this guard\n * discards the other. Widen to [8, 9] on hosts whose schedulers run late.\n */\nconst REPORT_HOURS = [8];\n\n/**\n * Weekends off by default: NYMEX does not trade Sat/Sun, so a weekend report\n * would repeat Friday's settlements verbatim. Flip to true for all 7 days.\n */\nconst INCLUDE_WEEKENDS = false;\n\n/** Read an env var on either Deno (Val Town) or Node, without assuming a runtime. */\nfunction envFlag(name: string): boolean {\n try {\n // @ts-ignore - Deno is present on Val Town, absent on Node.\n if (typeof Deno !== \"undefined\") return !!Deno.env.get(name);\n } catch { /* Deno.env may be permission-gated; fall through */ }\n // @ts-ignore - process is present on Node, absent on Deno.\n return typeof process !== \"undefined\" && !!process?.env?.[name];\n}\n\n/**\n * True only inside the report window.\n *\n * Set an environment variable FORCE_SEND=1 to make a manual Run send\n * immediately whatever the clock says, then delete the variable again.\n * That is the supported way to test without touching this file.\n */\nfunction isReportTime(t = easternNow()): boolean {\n if (envFlag(\"FORCE_SEND\")) return true;\n if (!REPORT_HOURS.includes(t.hour)) return false;\n if (INCLUDE_WEEKENDS) return true;\n return ![\"Sat\", \"Sun\"].includes(t.weekday);\n}\n\n// --------------------------------------------------- exchange calendar math\n\n/** Easter Sunday (Gregorian, Meeus/Jones/Butcher) -> [monthIdx0, day]. */\nfunction easter(year: number): [number, number] {\n const a = year % 19, b = Math.floor(year / 100), c = year % 100;\n const d = Math.floor(b / 4), e = b % 4;\n const f = Math.floor((b + 8) / 25), g = Math.floor((b - f + 1) / 3);\n const h = (19 * a + b - d - g + 15) % 30;\n const i = Math.floor(c / 4), k = c % 4;\n const l = (32 + 2 * e + 2 * i - h - k) % 7;\n const m = Math.floor((a + 11 * h + 22 * l) / 451);\n const month = Math.floor((h + l - 7 * m + 114) / 31);\n const day = ((h + l - 7 * m + 114) % 31) + 1;\n return [month - 1, day];\n}\n\n/** Date of the nth given weekday in a month (n = 1..5). */\nfunction nthWeekday(\n year: number,\n monthIdx0: number,\n weekday: number,\n n: number,\n): number {\n const first = new Date(Date.UTC(year, monthIdx0, 1)).getUTCDay();\n return 1 + ((weekday - first + 7) % 7) + (n - 1) * 7;\n}\n\n/** Holiday closures relevant to NYMEX floor/settlement scheduling, as YYYY-MM-DD. */\nfunction holidaySet(year: number): Set {\n const iso = (m: number, d: number) =>\n `${year}-${String(m + 1).padStart(2, \"0\")}-${String(d).padStart(2, \"0\")}`;\n const shiftIfWeekend = (m: number, d: number): [number, number] => {\n const wd = new Date(Date.UTC(year, m, d)).getUTCDay();\n if (wd === 6) return [m, d - 1]; // Sat -> observed Fri\n if (wd === 0) return [m, d + 1]; // Sun -> observed Mon\n return [m, d];\n };\n const out = new Set();\n for (\n const [m, d] of [[0, 1], [5, 19], [6, 4], [11, 25]] as [number, number][]\n ) {\n const [om, od] = shiftIfWeekend(m, d);\n out.add(iso(om, od));\n }\n out.add(iso(0, nthWeekday(year, 0, 1, 3))); // MLK Day, 3rd Mon Jan\n out.add(iso(1, nthWeekday(year, 1, 1, 3))); // Presidents Day, 3rd Mon Feb\n out.add(\n iso(\n 4,\n nthWeekday(year, 4, 1, 5) > new Date(Date.UTC(year, 5, 0)).getUTCDate()\n ? nthWeekday(year, 4, 1, 4)\n : nthWeekday(year, 4, 1, 5),\n ),\n ); // Memorial Day, last Mon May\n out.add(iso(8, nthWeekday(year, 8, 1, 1))); // Labor Day, 1st Mon Sep\n out.add(iso(10, nthWeekday(year, 10, 4, 4))); // Thanksgiving, 4th Thu Nov\n const [em, ed] = easter(year); // Good Friday = Easter - 2\n const gf = new Date(Date.UTC(year, em, ed - 2));\n out.add(iso(gf.getUTCMonth(), gf.getUTCDate()));\n return out;\n}\n\nfunction isBusinessDay(dt: Date, hols: Set): boolean {\n const wd = dt.getUTCDay();\n if (wd === 0 || wd === 6) return false;\n const key = `${dt.getUTCFullYear()}-${\n String(dt.getUTCMonth() + 1).padStart(2, \"0\")\n }-${String(dt.getUTCDate()).padStart(2, \"0\")}`;\n return !hols.has(key);\n}\n\n/**\n * NG termination: trading stops 3 business days before the first day of the\n * delivery month. Returns that last trade date.\n */\nfunction lastTradeDate(year: number, monthIdx0: number): Date {\n const hols = new Set([...holidaySet(year), ...holidaySet(year - 1)]);\n const dt = new Date(Date.UTC(year, monthIdx0, 1));\n let stepped = 0;\n while (stepped < 3) {\n dt.setUTCDate(dt.getUTCDate() - 1);\n if (isBusinessDay(dt, hols)) stepped++;\n }\n return dt;\n}\n\n/** The nearest NG contract that has not yet stopped trading, as of Eastern today. */\nfunction promptMonth(t = easternNow()): { year: number; monthIdx0: number } {\n let year = t.y, monthIdx0 = t.m - 1;\n const today = Date.UTC(t.y, t.m - 1, t.d);\n for (let i = 0; i < 4; i++) {\n if (today <= lastTradeDate(year, monthIdx0).getTime()) {\n return { year, monthIdx0 };\n }\n monthIdx0++;\n if (monthIdx0 > 11) {\n monthIdx0 = 0;\n year++;\n }\n }\n return { year, monthIdx0 };\n}\n\nexport interface Contract {\n n: number;\n symbol: string; // Yahoo symbol, e.g. NGV26.NYM\n ticker: string; // SEG-style ticker, e.g. NGV2026\n year: number;\n monthIdx0: number;\n label: string; // \"Oct 2026\"\n monthName: string; // \"October\"\n}\n\n/** Build the rolling 48-month curve starting at the prompt month. */\nfunction buildCurve(len = CURVE_LENGTH): Contract[] {\n const { year, monthIdx0 } = promptMonth();\n const out: Contract[] = [];\n for (let i = 0; i < len; i++) {\n const m = (monthIdx0 + i) % 12;\n const y = year + Math.floor((monthIdx0 + i) / 12);\n out.push({\n n: i + 1,\n symbol: `NG${MONTH_CODES[m]}${String(y).slice(-2)}.NYM`,\n ticker: `NG${MONTH_CODES[m]}${y}`,\n year: y,\n monthIdx0: m,\n label: `${MONTH_ABBR[m]} ${y}`,\n monthName: MONTH_NAMES[m],\n });\n }\n return out;\n}\n\n// ------------------------------------------------------------- data fetching\n\nexport interface Quote extends Contract {\n price: number | null;\n prevClose: number | null;\n change: number | null;\n pct: number | null;\n stale: boolean; // no bar for today yet; showing the prior settlement\n error?: string;\n}\n\nconst UA =\n \"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 \" +\n \"(KHTML, like Gecko) Chrome/126.0 Safari/537.36\";\n\nconst sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));\n\n/**\n * One symbol, with retry + host failover. Never throws.\n *\n * IMPORTANT — why this reads the daily bar series and ignores\n * meta.regularMarketPrice / meta.chartPreviousClose:\n *\n * The deferred months on this curve barely trade. Yahoo's\n * regularMarketPrice for them is the last *executed trade*, which can be\n * months old (NGQ30 was showing an April print in August), while\n * chartPreviousClose is the close preceding the whole requested range,\n * not the prior session. Using either produces badly wrong prices and\n * changes for anything past the first year or so.\n *\n * The daily bar series, by contrast, is marked to settlement every\n * session for every contract whether or not it trades. Last bar vs the\n * bar before it is the settlement-to-settlement move a supply desk\n * actually quotes, and it reconciles with Barchart and CME.\n */\nasync function fetchQuote(c: Contract): Promise {\n const hosts = [\"query1.finance.yahoo.com\", \"query2.finance.yahoo.com\"];\n let lastErr = \"\";\n\n for (let attempt = 0; attempt < 3; attempt++) {\n const host = hosts[attempt % hosts.length];\n const url =\n `https://${host}/v8/finance/chart/${encodeURIComponent(c.symbol)}` +\n `?range=1mo&interval=1d`;\n try {\n const res = await fetch(url, {\n headers: { \"User-Agent\": UA, \"Accept\": \"application/json\" },\n signal: AbortSignal.timeout(15_000),\n });\n if (!res.ok) {\n lastErr = `HTTP ${res.status}`;\n await sleep(400 * (attempt + 1));\n continue;\n }\n\n const json = await res.json();\n const result = json?.chart?.result?.[0];\n if (!result) {\n lastErr = json?.chart?.error?.description ?? \"no result\";\n await sleep(400);\n continue;\n }\n\n const stamps: number[] = result.timestamp ?? [];\n const closes: (number | null)[] = result.indicators?.quote?.[0]?.close ??\n [];\n\n // Settlement bars, oldest to newest, with the empty ones dropped.\n const bars = stamps\n .map((t, i) => ({ t, c: closes[i] }))\n .filter((b): b is { t: number; c: number } => typeof b.c === \"number\");\n\n if (bars.length === 0) {\n lastErr = \"no settlement bars\";\n await sleep(400);\n continue;\n }\n\n const last = bars.at(-1)!;\n const prior = bars.at(-2) ?? null;\n\n const price = last.c;\n const prevClose = prior ? prior.c : null;\n const change = prevClose === null ? null : price - prevClose;\n const pct = prevClose ? (change! / prevClose) * 100 : null;\n\n // Did this contract print in the current Eastern session?\n const barDay = new Intl.DateTimeFormat(\"en-CA\", {\n timeZone: \"America/New_York\",\n year: \"numeric\",\n month: \"2-digit\",\n day: \"2-digit\",\n }).format(new Date(last.t * 1000));\n const t = easternNow();\n const today = `${t.y}-${String(t.m).padStart(2, \"0\")}-${\n String(t.d).padStart(2, \"0\")\n }`;\n const stale = barDay !== today;\n\n return { ...c, price, prevClose, change, pct, stale };\n } catch (e) {\n lastErr = e instanceof Error ? e.message : String(e);\n await sleep(500 * (attempt + 1));\n }\n }\n return {\n ...c,\n price: null,\n prevClose: null,\n change: null,\n pct: null,\n stale: false,\n error: lastErr,\n };\n}\n\n/** Fetch the whole curve in polite batches so Yahoo does not rate-limit us. */\nasync function fetchCurve(contracts: Contract[], batch = 8): Promise {\n const out: Quote[] = [];\n for (let i = 0; i < contracts.length; i += batch) {\n const slice = contracts.slice(i, i + batch);\n out.push(...await Promise.all(slice.map(fetchQuote)));\n if (i + batch < contracts.length) await sleep(250);\n }\n return out;\n}\n\n// ------------------------------------------------------------------- strips\n\nexport interface Strip {\n name: string;\n note: string;\n avg: number | null;\n chg: number | null;\n}\n\nfunction averageOf(qs: Quote[]): { avg: number | null; chg: number | null } {\n const priced = qs.filter((q) => q.price !== null);\n if (priced.length === 0 || priced.length < qs.length * 0.6) {\n return { avg: null, chg: null };\n }\n const avg = priced.reduce((s, q) => s + q.price!, 0) / priced.length;\n const withChg = priced.filter((q) => q.change !== null);\n const chg = withChg.length\n ? withChg.reduce((s, q) => s + q.change!, 0) / withChg.length\n : null;\n return { avg, chg };\n}\n\n/** The summary strips a supply desk actually looks at each morning. */\nfunction buildStrips(qs: Quote[]): Strip[] {\n const strips: Strip[] = [];\n const at = (y: number, m: number) =>\n qs.find((q) => q.year === y && q.monthIdx0 === m);\n const range = (from: number, count: number) => qs.slice(from, from + count);\n\n strips.push({\n name: \"Prompt Month\",\n note: qs[0].label,\n ...averageOf(range(0, 1)),\n });\n strips.push({\n name: \"12-Month Strip\",\n note: `${qs[0].label} – ${qs[11].label}`,\n ...averageOf(range(0, 12)),\n });\n\n // Next full winter (Nov-Mar) and next full summer (Apr-Oct).\n const seasonal = (months: number[], startYear: number, label: string) => {\n const picked: Quote[] = [];\n let y = startYear;\n for (let i = 0; i < months.length; i++) {\n if (i > 0 && months[i] < months[i - 1]) y++;\n const q = at(y, months[i]);\n if (q) picked.push(q);\n }\n if (picked.length === months.length) {\n strips.push({\n name: label,\n note: `${picked[0].label} – ${picked.at(-1)!.label}`,\n ...averageOf(picked),\n });\n }\n };\n const first = qs[0];\n const winterStart = first.monthIdx0 <= 10 ? first.year : first.year + 1;\n seasonal(\n [10, 11, 0, 1, 2],\n winterStart,\n `Winter ${String(winterStart).slice(-2)}/${\n String(winterStart + 1).slice(-2)\n }`,\n );\n const summerYear = first.monthIdx0 <= 3 ? first.year : first.year + 1;\n seasonal([3, 4, 5, 6, 7, 8, 9], summerYear, `Summer ${summerYear}`);\n\n // Every calendar year the curve covers in full.\n const years = [...new Set(qs.map((q) => q.year))].sort();\n for (const y of years) {\n const yearMonths = qs.filter((q) => q.year === y);\n if (yearMonths.length === 12) {\n strips.push({\n name: `Cal ${y}`,\n note: \"12-month average\",\n ...averageOf(yearMonths),\n });\n }\n }\n return strips;\n}\n\n// -------------------------------------------------------------- html report\n\nconst money = (v: number | null, dp = 3) => v === null ? \"—\" : v.toFixed(dp);\n/** Anything that rounds to zero at the shown precision is \"unchanged\", not \"-0.000\". */\nconst isFlat = (v: number | null, dp = 3) =>\n v !== null && Math.abs(v) < 0.5 * Math.pow(10, -dp);\nconst signed = (v: number | null, dp = 3) => {\n if (v === null) return \"—\";\n if (isFlat(v, dp)) return (0).toFixed(dp);\n return `${v > 0 ? \"+\" : \"−\"}${Math.abs(v).toFixed(dp)}`;\n};\nconst toneOf = (v: number | null, dp = 3) =>\n v === null || isFlat(v, dp) ? C.muted : v > 0 ? C.up : C.down;\n\nfunction stripTile(s: Strip): string {\n return `\n \n \n \n

${s.name}

${s.note}

\n $${money(s.avg)}\n

\n ${signed(s.chg)} vs prior\n

\n `;\n}\n\nfunction curveRow(q: Quote, shade: boolean): string {\n const bg = shade ? \"#F7FAFD\" : \"#FFFFFF\";\n const cell =\n `padding:7px 10px;font-family:Arial,Helvetica,sans-serif;font-size:13px;border-bottom:1px solid #EDF2F7;`;\n const flag = q.error\n ? ` no data`\n : q.stale\n ? ` settle`\n : \"\";\n return `\n \n ${q.n}\n ${q.ticker}\n ${q.label}${flag}\n ${\n q.price === null ? \"—\" : \"$\" + money(q.price)\n }\n ${signed(q.change)}\n ${\n q.pct === null ? \"—\" : signed(q.pct, 2) + \"%\"\n }\n `;\n}\n\nexport function renderReport(\n qs: Quote[],\n strips: Strip[],\n stamp: string,\n sampleNote = \"\",\n): string {\n const th =\n `padding:8px 10px;font-family:Arial,Helvetica,sans-serif;font-size:10px;font-weight:bold;` +\n `letter-spacing:.7px;text-transform:uppercase;color:#FFFFFF;background:${C.blue};`;\n\n // strips laid out two per row\n let tiles = \"\";\n for (let i = 0; i < strips.length; i += 2) {\n tiles += `${stripTile(strips[i])}${\n strips[i + 1]\n ? stripTile(strips[i + 1])\n : ''\n }`;\n }\n\n const priced = qs.filter((q) => q.change !== null && q.price !== null);\n const sorted = [...priced].sort((a, b) =>\n Math.abs(b.change!) - Math.abs(a.change!)\n );\n const movers = sorted.slice(0, 3)\n .map((q) =>\n `${q.label} ${signed(q.change)}`\n )\n .join(\" · \");\n\n const missing = qs.filter((q) => q.price === null);\n const warn = missing.length\n ? `\n ${missing.length} contract${\n missing.length > 1 ? \"s\" : \"\"\n } did not return a price:\n ${missing.map((m) => m.ticker).join(\", \")}\n `\n : \"\";\n\n const sample = sampleNote\n ? `${sampleNote}\n `\n : \"\";\n\n let rows = \"\", shade = false, lastYear = qs[0]?.year;\n for (const q of qs) {\n if (q.year !== lastYear) {\n shade = !shade;\n lastYear = q.year;\n }\n rows += curveRow(q, shade);\n }\n\n return `\n\nHenry Hub Forward Curve\n\n\n\n

\n \n\n \n\n \n\n ${\n movers\n ? ``\n : \"\"\n }\n\n \n\n \n\n

Henry Hub Forward Curve

NYMEX Natural Gas (NG) · 48-month strip · ${stamp}

\n ${sample}${warn}

\n ${tiles}

\n Biggest moves
\n ${movers}\n

\n \n \n \n \n \n \n \n \n \n ${rows}\n

#	Ticker	Contract	Last	Chg	%

\n Prices in $/MMBtu. Change is versus the prior session's close. Contracts marked\n settle did not trade in the latest session and show the last settlement.\n The 48-month window rolls forward automatically as each prompt month expires.
\n Source: Yahoo Finance delayed NYMEX data. Automated daily report — Sunlight Energy Group.\n

\n`;\n}\n\n// ------------------------------------------------- history + excel workbook\n\nexport interface Snapshot {\n date: string;\n quotes: Quote[];\n strips: Strip[];\n}\n\n/** Monday of the week containing an ISO (YYYY-MM-DD) date, as ISO. */\nfunction weekStart(iso: string): string {\n const [y, m, d] = iso.split(\"-\").map(Number);\n const dt = new Date(Date.UTC(y, m - 1, d));\n const mondayOffset = (dt.getUTCDay() + 6) % 7; // Mon=0 ... Sun=6\n dt.setUTCDate(dt.getUTCDate() - mondayOffset);\n return dt.toISOString().slice(0, 10);\n}\n\nconst isoOf = (t: { y: number; m: number; d: number }) =>\n `${t.y}-${String(t.m).padStart(2, \"0\")}-${String(t.d).padStart(2, \"0\")}`;\n\n/** \"Mon 08/18\" — the per-day column header inside a week tab. */\nfunction dayLabel(iso: string): string {\n const [y, m, d] = iso.split(\"-\").map(Number);\n const wd =\n [\n \"Sun\",\n \"Mon\",\n \"Tue\",\n \"Wed\",\n \"Thu\",\n \"Fri\",\n \"Sat\",\n ][new Date(Date.UTC(y, m - 1, d)).getUTCDay()];\n return `${wd} ${String(m).padStart(2, \"0\")}/${String(d).padStart(2, \"0\")}`;\n}\n\n/** Excel tab name: \"Aug 17 2026\" for the week beginning that Monday. */\nfunction sheetName(weekIso: string): string {\n const [y, m, d] = weekIso.split(\"-\").map(Number);\n return `${MONTH_ABBR[m - 1]} ${d} ${y}`.slice(0, 31);\n}\n\n/**\n * History is stored one blob PER WEEK, not per day.\n *\n * Val Town's free plan caps a run at 60 seconds. Day-keyed storage meant the\n * number of blob reads grew with history — 13 weeks would be 65 round trips\n * every morning, on top of 48 Yahoo lookups, against that same 60s budget.\n * Week-keyed storage fixes the read count at HISTORY_WEEKS (13) no matter how\n * many years this runs, so the job's cost stops growing.\n */\ninterface WeekBlob {\n week: string;\n days: Record;\n}\n\nconst weekKey = (iso: string) => `${BLOB_PREFIX}wk-${weekStart(iso)}`;\n\n/** Merge today's curve into its week's blob. Never throws — history is a bonus. */\nasync function saveSnapshot(snap: Snapshot): Promise {\n try {\n const key = weekKey(snap.date);\n let wk: WeekBlob;\n try {\n wk = await blob.getJSON(key) as WeekBlob;\n if (!wk?.days) throw new Error(\"empty\");\n } catch {\n wk = { week: weekStart(snap.date), days: {} };\n }\n wk.days[snap.date] = { quotes: snap.quotes, strips: snap.strips };\n await blob.setJSON(key, wk);\n } catch (e) {\n console.error(\"snapshot save failed:\", e);\n }\n}\n\n/** Load the most recent HISTORY_WEEKS weeks — a fixed number of reads. */\nasync function loadHistory(todayIso: string): Promise {\n try {\n const keys: string[] = [];\n const cursor = new Date(`${weekStart(todayIso)}T00:00:00Z`);\n for (let i = 0; i < HISTORY_WEEKS; i++) {\n keys.push(`${BLOB_PREFIX}wk-${cursor.toISOString().slice(0, 10)}`);\n cursor.setUTCDate(cursor.getUTCDate() - 7);\n }\n\n const blobs = await Promise.all(\n keys.map((k) =>\n blob.getJSON(k).catch(() => null) as Promise\n ),\n );\n\n const out: Snapshot[] = [];\n for (const wk of blobs) {\n if (!wk?.days) continue;\n for (const [date, v] of Object.entries(wk.days)) {\n if (Array.isArray(v?.quotes)) {\n out.push({ date, quotes: v.quotes, strips: v.strips ?? [] });\n }\n }\n }\n return out.sort((a, b) => a.date.localeCompare(b.date));\n } catch (e) {\n console.error(\"history load failed:\", e);\n return [];\n }\n}\n\n/** One week tab: contracts down the side, each session across the top. */\nfunction weekSheet(\n weekIso: string,\n days: Snapshot[],\n): (string | number | null)[][] {\n const cols = days.map((d) => d.date);\n const newest = days.at(-1)!;\n\n // Row order follows the newest session; anything that rolled off mid-week is\n // appended after it so no day's data silently disappears from the file.\n const order: string[] = newest.quotes.map((q) => q.ticker);\n const seen = new Set(order);\n for (const d of days) {\n for (const q of d.quotes) {\n if (!seen.has(q.ticker)) {\n seen.add(q.ticker);\n order.push(q.ticker);\n }\n }\n }\n\n const meta = new Map();\n for (const d of days) {\n for (const q of d.quotes) if (!meta.has(q.ticker)) meta.set(q.ticker, q);\n }\n\n const priceOn = (date: string, ticker: string): number | null => {\n const day = days.find((d) => d.date === date);\n const q = day?.quotes.find((x) => x.ticker === ticker);\n return q?.price ?? null;\n };\n\n const [wy, wm, wd] = weekIso.split(\"-\").map(Number);\n const rows: (string | number | null)[][] = [\n [`Henry Hub Forward Curve — week of ${MONTH_NAMES[wm - 1]} ${wd}, ${wy}`],\n [\"NYMEX Natural Gas (NG). Settlement prices in $/MMBtu.\"],\n [],\n [\"Ticker\", \"Contract Month\", \"Year\", ...cols.map(dayLabel), \"Wk Chg\"],\n ];\n\n for (const ticker of order) {\n const q = meta.get(ticker)!;\n const series = cols.map((c) => priceOn(c, ticker));\n const present = series.filter((v): v is number => v !== null);\n const wkChg = present.length >= 2\n ? +(present.at(-1)! - present[0]).toFixed(3)\n : null;\n rows.push([ticker, q.monthName, q.year, ...series, wkChg]);\n }\n\n rows.push([]);\n rows.push([\"Summary strips\", ...Array(2 + cols.length).fill(\"\"), \"\"]);\n rows.push([\"Strip\", \"Range\", \"\", ...cols.map(dayLabel), \"Wk Chg\"]);\n\n const stripNames: string[] = [];\n for (const d of days) {\n for (const s of d.strips) {\n if (!stripNames.includes(s.name)) stripNames.push(s.name);\n }\n }\n for (const name of stripNames) {\n const note = days.map((d) =>\n d.strips.find((s) => s.name === name)?.note\n ).find(Boolean) ?? \"\";\n const series = cols.map((c) => {\n const day = days.find((d) =>\n d.date === c\n );\n const v = day?.strips.find((s) => s.name === name)?.avg;\n return v === undefined || v === null ? null : +v.toFixed(3);\n });\n const present = series.filter((v): v is number => v !== null);\n const wkChg = present.length >= 2\n ? +(present.at(-1)! - present[0]).toFixed(3)\n : null;\n rows.push([name, note, \"\", ...series, wkChg]);\n }\n return rows;\n}\n\n/**\n * Build the workbook, newest week as the first tab.\n *\n * Tabs are appended in reverse chronological order, so this morning's week is\n * always the one Excel opens on and older weeks trail off to the right.\n * Returns base64 ready for the mail attachment, or null if anything went wrong\n * (the report still sends without the file rather than not sending at all).\n */\nfunction buildWorkbook(snaps: Snapshot[]): string | null {\n try {\n if (snaps.length === 0) return null;\n\n const byWeek = new Map();\n for (const s of snaps) {\n const w = weekStart(s.date);\n (byWeek.get(w) ?? byWeek.set(w, []).get(w)!).push(s);\n }\n\n const weeks = [...byWeek.keys()].sort().reverse(); // newest first\n const wb = XLSX.utils.book_new();\n\n for (const w of weeks) {\n const days = byWeek.get(w)!.sort((a, b) => a.date.localeCompare(b.date));\n const aoa = weekSheet(w, days);\n const ws = XLSX.utils.aoa_to_sheet(aoa);\n\n ws[\"!cols\"] = [\n { wch: 11 },\n { wch: 15 },\n { wch: 7 },\n ...days.map(() => ({ wch: 11 })),\n { wch: 9 },\n ];\n\n // Three decimals on every numeric price cell.\n for (const ref of Object.keys(ws)) {\n if (ref.startsWith(\"!\")) continue;\n const cell = ws[ref];\n if (cell?.t === \"n\" && !/^C\\d+$/.test(ref)) cell.z = \"0.000\"; // column C is Year\n }\n\n XLSX.utils.book_append_sheet(wb, ws, sheetName(w));\n }\n\n return XLSX.write(wb, { type: \"base64\", bookType: \"xlsx\" });\n } catch (e) {\n console.error(\"workbook build failed:\", e);\n return null;\n }\n}\n\n/** Plain-text fallback for clients that will not render HTML. */\nfunction renderText(qs: Quote[], strips: Strip[], stamp: string): string {\n const lines = [\n `HENRY HUB FORWARD CURVE — ${stamp}`,\n `NYMEX Natural Gas (NG), $/MMBtu, 48-month strip`,\n \"\",\n \"SUMMARY\",\n ...strips.map((s) =>\n ` ${s.name.padEnd(18)} $${money(s.avg)} (${signed(s.chg)}) ${s.note}`\n ),\n \"\",\n \"FULL CURVE\",\n ` ${\"#\".padStart(3)} ${\"TICKER\".padEnd(9)} ${\"CONTRACT\".padEnd(16)} ${\n \"LAST\".padStart(8)\n } ${\"CHG\".padStart(8)} ${\"%\".padStart(8)}`,\n ...qs.map((q) =>\n ` ${String(q.n).padStart(3)} ${q.ticker.padEnd(9)} ${\n (q.monthName + \" \" + q.year).padEnd(16)\n }` +\n ` ${money(q.price).padStart(8)} ${signed(q.change).padStart(8)}` +\n ` ${(q.pct === null ? \"—\" : signed(q.pct, 2) + \"%\").padStart(8)}`\n ),\n \"\",\n \"Source: Yahoo Finance delayed NYMEX data. Automated report — Sunlight Energy Group.\",\n ];\n return lines.join(\"\\n\");\n}\n\n// ------------------------------------------------------------------ handler\n\nexport default async function () {\n const t = easternNow();\n\n // The cron fires at both 12:30 and 13:30 UTC so that one of them is always\n // 8:30 AM Eastern. This guard discards the other, and skips weekends.\n if (!isReportTime(t)) return;\n\n const stamp = `${MONTH_NAMES[t.m - 1]} ${t.d}, ${t.y}`;\n\n try {\n const t0 = Date.now();\n const contracts = buildCurve();\n const quotes = await fetchCurve(contracts);\n const strips = buildStrips(quotes);\n console.log(`quotes fetched in ${((Date.now() - t0) / 1000).toFixed(1)}s`);\n\n const failed = quotes.filter((q) => q.price === null).length;\n const subject = failed > 6\n ? `⚠ Henry Hub Curve — ${stamp} (${failed} contracts missing)`\n : `Henry Hub Forward Curve — ${stamp} · Prompt $${\n money(quotes[0].price)\n }`;\n\n // Record today, then rebuild the rolling workbook from stored history.\n const today = isoOf(t);\n await saveSnapshot({ date: today, quotes, strips });\n const history = await loadHistory(today);\n if (!history.some((h) => h.date === today)) {\n history.push({ date: today, quotes, strips }); // blob lagged; use in-memory\n }\n const workbook = buildWorkbook(history);\n console.log(\n `total ${\n ((Date.now() - t0) / 1000).toFixed(1)\n }s · ${history.length} sessions of history · ` +\n `workbook ${\n workbook\n ? Math.round(workbook.length * 0.75 / 1024) + \" KB\"\n : \"FAILED\"\n }`,\n );\n\n await email({\n subject,\n html: renderReport(quotes, strips, stamp),\n text: renderText(quotes, strips, stamp),\n ...(RECIPIENTS.length ? { to: RECIPIENTS } : {}),\n ...(workbook\n ? {\n attachments: [{\n content: workbook,\n filename: `HenryHub_Curve_${today}.xlsx`,\n type:\n \"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet\",\n disposition: \"attachment\",\n }],\n }\n : {}),\n });\n } catch (err) {\n await email({\n subject: `⚠ Henry Hub Curve report FAILED — ${stamp}`,\n text: `The daily gas curve report could not be generated.\\n\\n` +\n `${err instanceof Error ? err.stack ?? err.message : String(err)}\\n\\n` +\n `No prices were sent. 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