#!/usr/bin/env bash
#
# sqlite-diff — compare the upstream SQLite source artifacts between two trees.
#
# Unlike a plain `diff -urN A B`, this only looks at the files that *upstream*
# SQLite ships in its src/ directory (the hand-written .c/.h/.y/.in/... sources).
# That skips:
#   - generated/built files (sqlite3.c amalgamation, parse.c, opcodes.*, tsrc/, ...)
#   - autoconf output (Makefile, libtool, config.*)
#   - .git internals
#   - libSQL's own additions (vectordiskann.c, ext/crr, ...) that upstream lacks
#
# The result is a unified diff suitable for piping to `diffstat`, `less`, or
# `git apply`.
#
# Usage:
#   scripts/sqlite-diff <upstream-dir> <other-dir>
#   scripts/sqlite-diff <upstream-dir> <other-dir> | diffstat
#
# The first argument is the reference tree: its src/ file list defines what
# counts as a "source artifact". The second is the tree compared against it.

set -euo pipefail

usage() {
	echo "usage: $(basename "$0") <upstream-dir> <other-dir>" >&2
	echo "       compares upstream's src/ source files against <other-dir>/src/" >&2
	exit 2
}

[ $# -eq 2 ] || usage

upstream=$1
other=$2

# Which subdirectory holds the source artifacts (override with SUBDIR=... if needed).
subdir=${SUBDIR:-src}

for d in "$upstream" "$other"; do
	[ -d "$d" ] || { echo "error: not a directory: $d" >&2; exit 1; }
done
[ -d "$upstream/$subdir" ] || { echo "error: no $subdir/ in upstream: $upstream" >&2; exit 1; }

# Iterate over the files upstream ships in src/, diffing each against the other
# tree. Using a NUL-delimited list keeps unusual filenames safe. -N treats a
# file missing from <other> as an empty file, so deletions show up in full.
status=0
while IFS= read -r -d '' rel; do
	# rel is relative to "$upstream", e.g. "src/btree.c"
	a="$upstream/$rel"
	b="$other/$rel"
	# --label makes the diff read like git's a/ b/ and keeps diffstat -p1 happy,
	# regardless of where the two trees live on disk.
	if ! diff -uN --label "a/$rel" --label "b/$rel" "$a" "$b"; then
		status=1
	fi
done < <(cd "$upstream" && find "$subdir" -type f -print0 | sort -z)

# diff/while exit non-zero when differences were found; that's expected, not an
# error, so report success unless an actual diff invocation failed otherwise.
exit 0