#!/usr/bin/env bash
#
# Regenerates the Android adaptive-icon foreground from the iOS icon.
#
#   scripts/gen-adaptive-icon.sh            # check, and generate if missing
#   scripts/gen-adaptive-icon.sh --force    # regenerate even if one exists but differs
#
# Android launcher masks (round, squircle, teardrop — the launcher decides) crop the icon. The art is
# a full-bleed render on a black backdrop, so a mask ate its edges. The fix is to shrink the art inside
# the same canvas and let the transparent margin absorb whatever the mask takes.
#
# Only Android needs this. iOS draws icon.png full-bleed with its own rounding, so insetting there
# would just add a black border — icon.png is never touched.
#
# Runs from the `prebuild` npm script, because `expo prebuild` is what turns these assets into
# android/app/src/main/res/*.webp. The generated PNG is also committed, so a machine without
# ImageMagick still builds a correct icon — this regenerates it, it is not the only source. That is
# also why calling `expo prebuild` directly instead of `bun run prebuild` is a mistake: it skips this
# silently.
set -euo pipefail

# Android's adaptive-icon spec: the outer 1/3 of the foreground is reserved for mask and parallax,
# leaving a guaranteed-visible circle of ~66%. 72% sits just above that — as large as the art can be
# drawn while no supported mask clips it.
readonly INSET_PERCENT=72

ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
ICON="$ROOT/assets/icon.png"
ADAPTIVE="$ROOT/assets/adaptive-icon.png"

FORCE=false
for a in "$@"; do [[ "$a" == "--force" ]] && FORCE=true; done

if ! command -v magick >/dev/null 2>&1; then
	echo "!! ImageMagick not found — skipping adaptive-icon generation." >&2
	echo "!! The committed adaptive-icon.png is used as-is.  brew install imagemagick" >&2
	exit 0
fi

# True when `existing` already IS `icon` inset — compared by pixel content, not by bytes and not by
# geometry.
#
# Geometry alone is not enough: checking only that the art fills ~72% of the canvas passes an adaptive
# icon built from SUPERSEDED art, so swapping in new icon.png art leaves the Android icon silently
# stale. Bytes are not enough in the other direction: re-encoding an identical image can differ, which
# would rewrite a megabyte on every prebuild. RMSE of the decoded pixels is exact here, so the
# threshold only absorbs a future encoder change.
matches_icon() {
	local existing="$1" icon="$2" size="$3" art="$4"
	local tmp="$existing.expected.png"
	magick "$icon" -resize "${art}x${art}" -background none -gravity center \
		-extent "${size}x${size}" "$tmp" 2>/dev/null || { rm -f "$tmp"; return 1; }

	# Differing canvas sizes make compare fail outright, which is itself a mismatch.
	local rmse
	rmse="$(magick compare -metric RMSE "$existing" "$tmp" null: 2>&1 || true)"
	rmse="${rmse%% *}"
	rm -f "$tmp"

	awk -v v="$rmse" 'BEGIN { exit !(v ~ /^[0-9.]+$/ && v < 100) }'
}

[[ -f "$ICON" ]] || { echo "!! no assets/icon.png" >&2; exit 1; }

# Same canvas as the source; only the art inside it shrinks. Rounded, not truncated.
size="$(magick identify -format '%w' "$ICON")"
art=$(((size * INSET_PERCENT + 50) / 100))

if [[ -f "$ADAPTIVE" ]] && matches_icon "$ADAPTIVE" "$ICON" "$size" "$art"; then
	echo "adaptive icon: ok"
elif [[ -f "$ADAPTIVE" ]] && [[ "$FORCE" != true ]]; then
	# Deliberately does NOT overwrite. An existing adaptive icon that does not match icon.png is
	# ambiguous: it is either stale art (regenerate) or art framed on purpose. Say so and let a human
	# decide; --force applies the regeneration.
	echo "adaptive icon: DIFFERS from icon.png — not overwritten (--force to regenerate)"
else
	magick "$ICON" -resize "${art}x${art}" \
		-background none -gravity center -extent "${size}x${size}" "$ADAPTIVE"
	echo "adaptive icon: regenerated (${size} canvas, ${art} art)"
fi

# The adaptive background sits behind the inset art, so it must match the art's own backdrop or a seam
# shows at the edges. This only reports — app.json is easy to edit by hand and silently rewriting it
# is worse than saying what to change.
corner="#$(magick "$ICON" -format '%[hex:p{0,0}]' info: | tr '[:lower:]' '[:upper:]')"
configured="$(grep -oE 'backgroundColor.{0,4}#[0-9A-Fa-f]{6}' "$ROOT/app.json" 2>/dev/null \
	| grep -oE '#[0-9A-Fa-f]{6}' | head -1 | tr '[:lower:]' '[:upper:]' || true)"
if [[ -z "$configured" ]]; then
	echo "  no android.adaptiveIcon.backgroundColor set — use $corner"
elif [[ "$corner" != "$configured" ]]; then
	echo "  backgroundColor is $configured, art corner is $corner"
fi