#!/usr/bin/env bash
# sync-upstream.sh — Update from upstream Redox and reapply Red Bear OS overlays.
#
# Usage:
#   ./local/scripts/sync-upstream.sh              # Rebase onto upstream master
#   ./local/scripts/sync-upstream.sh --dry-run    # Preview what would change
#   ./local/scripts/sync-upstream.sh --no-merge   # Only fetch + check for conflicts
#
# Strategy: git rebase (preserves Red Bear OS commits, replays on new upstream).
# Fallback: if rebase fails, patches in local/patches/build-system/ can be
#           applied from scratch via: ./local/scripts/apply-patches.sh --force
#
# IMPORTANT: upstream WIP recipes are not treated as durable shipping inputs by Red Bear.
# After upstream sync, Red Bear-owned WIP work still needs to come from local/recipes/ and
# local/patches/, not from trust in recipes/wip/ alone.

set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
REPO_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
UPSTREAM_URL="${UPSTREAM_URL:-https://github.com/redox-os/redox.git}"
UPSTREAM_REMOTE="upstream-redox"
UPSTREAM_BRANCH="${UPSTREAM_BRANCH:-master}"
DRY_RUN=0
NO_MERGE=0

usage() {
    echo "Usage: $0 [--dry-run] [--no-merge]"
    echo "  --dry-run    Show what would happen without making changes"
    echo "  --no-merge   Only fetch and check patch conflicts"
}

for arg in "$@"; do
    case "$arg" in
        --dry-run)   DRY_RUN=1 ;;
        --no-merge)  NO_MERGE=1 ;;
        --help|-h)
            usage
            exit 0
            ;;
        *)
            echo "Unknown argument: $arg"
            usage >&2
            exit 1
            ;;
    esac
done

cd "$REPO_ROOT"

# ── 1. Ensure upstream remote ───────────────────────────────────────
if ! git remote get-url "$UPSTREAM_REMOTE" &>/dev/null; then
    echo "==> Adding upstream remote: $UPSTREAM_URL"
    [ "$DRY_RUN" = "0" ] && git remote add "$UPSTREAM_REMOTE" "$UPSTREAM_URL"
fi

echo "==> Fetching $UPSTREAM_REMOTE/$UPSTREAM_BRANCH..."
[ "$DRY_RUN" = "0" ] && git fetch "$UPSTREAM_REMOTE" "$UPSTREAM_BRANCH"

UPSTREAM_REF="${UPSTREAM_REMOTE}/${UPSTREAM_BRANCH}"

# ── 2. Check patch conflicts with upstream changes ──────────────────
MERGE_BASE=$(git merge-base HEAD "$UPSTREAM_REF" 2>/dev/null || echo "")
if [ -n "$MERGE_BASE" ]; then
    CHANGED_FILES=$(git diff --name-only "$MERGE_BASE" "$UPSTREAM_REF" 2>/dev/null || true)
    CHANGE_COUNT=$(echo "$CHANGED_FILES" | grep -c . 2>/dev/null || echo "0")
    echo "    $CHANGE_COUNT files changed upstream since common ancestor"

    if [ -n "$CHANGED_FILES" ] && [ -d local/patches ]; then
        echo ""
        echo "==> Checking patch conflict risks..."
        for patch_file in local/patches/build-system/[0-9]*.patch; do
            [ -f "$patch_file" ] || continue
            PATCH_NAME=$(basename "$patch_file")
            PATCHED_FILES=$(grep '^--- a/' "$patch_file" 2>/dev/null | sed 's|^--- a/||' | sort -u || true)
            for pf in $PATCHED_FILES; do
                if echo "$CHANGED_FILES" | grep -q "$pf" 2>/dev/null; then
                    echo "    ⚠ CONFLICT RISK: $PATCH_NAME modifies $pf (also changed upstream)"
                fi
            done
        done

        for patch_dir in local/patches/kernel local/patches/base; do
            [ -f "$patch_dir/redox.patch" ] || continue
            echo "    ℹ $patch_dir/redox.patch — check manually if kernel/base changed upstream"
        done
    fi
else
    echo "    WARNING: Could not find common ancestor with upstream"
fi

# ── 3. Summary ─────────────────────────────────────────────────────
AHEAD=$(git rev-list --count "$UPSTREAM_REF..HEAD" 2>/dev/null || echo "?")
BEHIND=$(git rev-list --count "HEAD..$UPSTREAM_REF" 2>/dev/null || echo "?")
echo ""
echo "=== Sync Summary ==="
echo "Upstream:  $UPSTREAM_REF"
echo "Local:     HEAD ($(git rev-parse --short HEAD))"
echo "Ahead:     $AHEAD Red Bear OS commits"
echo "Behind:    $BEHIND upstream commits"

if [ "$NO_MERGE" = 1 ]; then
    echo ""
    echo "To merge manually:"
    echo "  git rebase $UPSTREAM_REF"
    exit 0
fi

if [ "$DRY_RUN" = "1" ]; then
    echo ""
    echo "    [dry-run] Would rebase onto $UPSTREAM_REF"
    exit 0
fi

# ── 4. Stash uncommitted changes ────────────────────────────────────
STASHED=0
if ! git diff --quiet 2>/dev/null || ! git diff --cached --quiet 2>/dev/null; then
    echo "==> Stashing uncommitted changes..."
    git stash push -m "redbear-sync-$(date +%Y%m%d-%H%M%S)"
    STASHED=1
fi

PREV_HEAD=$(git rev-parse HEAD)

# ── 5. Rebase ───────────────────────────────────────────────────────
echo ""
echo "==> Rebasing Red Bear OS commits onto $UPSTREAM_REF..."
echo "    (this replays our $AHEAD commits on top of updated upstream)"

if git rebase "$UPSTREAM_REF"; then
    echo ""
    echo "==> Rebase successful."
else
    echo ""
    echo "!! Rebase conflict. Options:"
    echo "   1. Resolve conflicts:  edit files, git add, git rebase --continue"
    echo "   2. Abort:              git rebase --abort"
    echo "   3. Nuclear option:"
    echo "      git rebase --abort"
    echo "      git reset --hard $UPSTREAM_REF"
    echo "      ./local/scripts/apply-patches.sh --force"
    echo ""
    echo "   Patches for recovery: local/patches/build-system/"
    echo "   Previous HEAD:        $PREV_HEAD"
    exit 1
fi

# ── 6. Restore stash ────────────────────────────────────────────────
if [ "$STASHED" = 1 ]; then
    echo "==> Restoring stashed changes..."
    git stash pop || echo "    (stash pop had conflicts — resolve manually)"
fi

# ── 7. Verify symlinks ─────────────────────────────────────────────
echo "==> Verifying recipe patch symlinks..."
if [ -f local/scripts/apply-patches.sh ]; then
    bash local/scripts/apply-patches.sh
else
    echo "    apply-patches.sh not found — verify symlinks manually"
    ls -la recipes/core/kernel/redox.patch recipes/core/base/redox.patch
fi

if [ -x local/scripts/verify-overlay-integrity.sh ]; then
    echo "==> Verifying overlay integrity..."
    local/scripts/verify-overlay-integrity.sh --repair
fi

echo ""
echo "==> Sync complete."
echo "    Previous HEAD: $PREV_HEAD"
echo "    New HEAD:      $(git rev-parse HEAD)"
echo ""
echo "Next: make all CONFIG_NAME=redbear-full"