#!/usr/bin/env bash
# ──────────────────────────────────────────────────────────────
# merge-reference-impl-start.sh
#
# Prepares the workspace for a reference implementation merge:
#   1. Creates a dated branch from main
#   2. Updates Copilot CLI and records the new version
#   3. Clones the reference implementation copilot-sdk repo into a temp dir
#   4. Reads .lastmerge and prints a short summary of new commits
#
# Usage:  ./.github/scripts/reference-impl-sync/merge-reference-impl-start.sh
# Output: Exports REFERENCE_IMPL_DIR and LAST_MERGE_COMMIT to a
#         .merge-env file so other scripts can source it.
# ──────────────────────────────────────────────────────────────
set -euo pipefail

ROOT_DIR="$(cd "$(dirname "$0")/../../.." && pwd)"
cd "$ROOT_DIR"

REFERENCE_IMPL_REPO="https://github.com/github/copilot-sdk.git"
ENV_FILE="$ROOT_DIR/.merge-env"

# ── 1. Create branch (or reuse existing) ─────────────────────
CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)

if [[ "$CURRENT_BRANCH" != "main" ]]; then
    # Already on a non-main branch (e.g., coding agent's auto-created PR branch).
    # Stay on this branch — do not create a new one.
    BRANCH_NAME="$CURRENT_BRANCH"
    echo "▸ Already on branch '$BRANCH_NAME' — reusing it (coding agent mode)."
    git pull origin main --no-edit 2>/dev/null || echo "  (pull from main skipped or fast-forward not possible)"
else
    echo "▸ Ensuring main is up to date…"
    git pull origin main

    BRANCH_NAME="merge-reference-impl-$(date +%Y%m%d)"
    echo "▸ Creating branch: $BRANCH_NAME"
    git checkout -b "$BRANCH_NAME"
fi

# ── 2. Update Copilot CLI ────────────────────────────────────
echo "▸ Updating Copilot CLI…"
if command -v copilot &>/dev/null; then
    copilot update || echo "  (copilot update returned non-zero – check manually)"
    CLI_VERSION=$(copilot --version | head -n 1 | awk '{print $NF}')
    echo "  Copilot CLI version: $CLI_VERSION"
else
    echo "  ⚠ 'copilot' command not found – skipping CLI update."
    CLI_VERSION="UNKNOWN"
fi

# ── 3. Clone reference implementation ────────────────────────────────────────
TEMP_DIR=$(mktemp -d)
REFERENCE_IMPL_DIR="$TEMP_DIR/copilot-sdk"
echo "▸ Cloning reference implementation into $REFERENCE_IMPL_DIR …"
git clone --depth=200 "$REFERENCE_IMPL_REPO" "$REFERENCE_IMPL_DIR"

# ── 4. Read last merge commit ────────────────────────────────
if [[ ! -f "$ROOT_DIR/.lastmerge" ]]; then
    echo "❌ .lastmerge file not found in repo root."
    exit 1
fi
LAST_MERGE_COMMIT=$(tr -d '[:space:]' < "$ROOT_DIR/.lastmerge")
echo "▸ Last merged reference implementation commit: $LAST_MERGE_COMMIT"

# Quick summary
echo ""
echo "── Reference implementation commits since last merge ──"
(cd "$REFERENCE_IMPL_DIR" && git fetch origin main && \
 git log --oneline "$LAST_MERGE_COMMIT"..origin/main) || \
    echo "  (could not generate log – the commit may have been rebased)"
echo ""

# ── 5. Write env file for other scripts ──────────────────────
cat > "$ENV_FILE" <<EOF
# Auto-generated by merge-reference-impl-start.sh – do not commit
BRANCH_NAME=$BRANCH_NAME
REFERENCE_IMPL_DIR=$REFERENCE_IMPL_DIR
LAST_MERGE_COMMIT=$LAST_MERGE_COMMIT
CLI_VERSION=$CLI_VERSION
EOF

echo "▸ Env file written to $ENV_FILE (sourced by other merge scripts)."
echo ""
echo "✅  Ready. Next steps:"
echo "  1. Run ./.github/scripts/reference-impl-sync/merge-reference-impl-diff.sh to see the full diff analysis."
echo "  2. Port changes to the Java SDK."
echo "  3. Run ./.github/scripts/reference-impl-sync/merge-reference-impl-finish.sh when done."