#!/bin/sh
# Fetch the ECB euro reference rates and write content/rates.json.
#
# Feeds the indicative national-currency line on the order page ("≈ CA$920 ·
# ECB reference rate 2026-08-04"). Indicative is the contract: every charge is
# in euros, the buyer's bank sets the real conversion — so build-time daily
# reference rates are exactly the right freshness, and no rate service is ever
# called at page-view time (nothing third-party runs against visitors).
#
# Values are emitted as INTEGER micro-units of target currency per euro
# (1 EUR = 1.0834 USD -> 1083400), so the C++ side never parses a decimal and
# no float ever touches a money path.
#
# Like fetch-posts.sh: exits 0 on network failure, leaving any previous
# rates.json in place — a stale indicative rate labelled with its date beats a
# failed deploy.

set -eu

OUT="content/rates.json"
URL="https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml"

TMP="$(mktemp)"
trap 'rm -f "$TMP"' EXIT

if ! curl -fsSL --max-time 30 \
        -A 'catcrafts.net-buildfetch/1.0 (+https://catcrafts.net)' \
        "$URL" -o "$TMP" 2>/dev/null; then
    echo "fetch-rates: ECB unreachable; keeping existing $OUT" >&2
    exit 0
fi

# The XML is a flat list: <Cube currency='USD' rate='1.1515'/> under one
# <Cube time='2026-08-04'>. The ECB emits single-quoted attributes today;
# normalising quotes first keeps this working if they ever switch to double.
tr "'" '"' < "$TMP" > "$TMP.n" && mv "$TMP.n" "$TMP"

DATE=$(grep -o 'time="[0-9-]*"' "$TMP" | head -n1 | cut -d'"' -f2)
if [ -z "$DATE" ]; then
    echo "fetch-rates: unexpected ECB payload; keeping existing $OUT" >&2
    exit 0
fi

RATES=$(grep -o 'currency="[A-Z]*" rate="[0-9.]*"' "$TMP" | awk -F'"' '
    {
        cur = $2; rate = $4
        # decimal -> integer micros, without floats: split on the point and
        # right-pad the fraction to exactly six digits.
        n = split(rate, parts, ".")
        intpart = parts[1]
        frac = (n > 1) ? parts[2] : ""
        frac = substr(frac "000000", 1, 6)
        micro = intpart frac
        # strip leading zeros (but keep at least one digit)
        sub(/^0+/, "", micro); if (micro == "") micro = "0"
        printf "%s\"%s\":%s", (out++ ? "," : ""), cur, micro
    }')

if [ -z "$RATES" ]; then
    echo "fetch-rates: no rates parsed; keeping existing $OUT" >&2
    exit 0
fi

printf '{"date":"%s","micro_per_eur":{%s}}\n' "$DATE" "$RATES" > "$OUT.new"

# Sanity: the file must parse and contain USD, or something upstream changed
# shape and the old file is the safer one.
if command -v jq >/dev/null 2>&1; then
    if ! jq -e '.micro_per_eur.USD > 500000' "$OUT.new" >/dev/null 2>&1; then
        echo "fetch-rates: output failed sanity check; keeping existing $OUT" >&2
        rm -f "$OUT.new"
        exit 0
    fi
fi

mv "$OUT.new" "$OUT"
count=$(grep -o ':' "$OUT" | wc -l)
echo "fetch-rates: wrote $OUT ($DATE, $((count - 1)) currencies)"