#!/usr/bin/env bash
# Runs inside the migration container.
# Copies all collections + indexes from $SRC_DB to $DST_DB,
# verifies document counts, then optionally drops the source.

set -euo pipefail

RED='\033[0;31m'; GREEN='\033[0;32m'; YELLOW='\033[1;33m'; NC='\033[0m'
info()  { echo -e "${GREEN}[migrate]${NC} $*"; }
warn()  { echo -e "${YELLOW}[migrate]${NC} $*"; }
die()   { echo -e "${RED}[migrate]${NC} $*" >&2; exit 1; }

MONGO_HOST="${MONGO_HOST:-mongo}"
MONGO_PORT="${MONGO_PORT:-27017}"
SRC_DB="${SRC_DB:-keymanager}"
DST_DB="${DST_DB:-vantage}"
DROP_SRC="${DROP_SRC:-false}"

MONGO_URI="mongodb://${MONGO_HOST}:${MONGO_PORT}"

mongosh_eval() {
    local db="$1"; local script="$2"
    mongosh --quiet "${MONGO_URI}/${db}" --eval "$script"
}

# ---------------------------------------------------------------------------
# 1. Wait for MongoDB to be reachable
# ---------------------------------------------------------------------------
info "Waiting for MongoDB at ${MONGO_HOST}:${MONGO_PORT}..."
for i in $(seq 1 30); do
    mongosh --quiet "${MONGO_URI}/admin" --eval "db.adminCommand('ping')" >/dev/null 2>&1 && break
    [ "$i" -eq 30 ] && die "MongoDB not reachable after 30 attempts."
    sleep 2
done
info "MongoDB is ready."

# ---------------------------------------------------------------------------
# 2. Check source database
# ---------------------------------------------------------------------------
SRC_COLLECTIONS=$(mongosh_eval admin "
  const names = db.getSiblingDB('${SRC_DB}').getCollectionNames();
  print(names.join(','));
")

if [ -z "$SRC_COLLECTIONS" ] || [ "$SRC_COLLECTIONS" = "," ]; then
    warn "Source database '${SRC_DB}' has no collections — nothing to migrate."
    warn "If this is a fresh deployment, '${DST_DB}' will be created automatically."
    exit 0
fi

info "Collections in '${SRC_DB}': ${SRC_COLLECTIONS}"

# ---------------------------------------------------------------------------
# 3. Copy all collections via \$out
# ---------------------------------------------------------------------------
info "Copying collections from '${SRC_DB}' to '${DST_DB}'..."

mongosh_eval admin "
  const src = db.getSiblingDB('${SRC_DB}');
  const cols = src.getCollectionNames();
  cols.forEach(function(name) {
    src[name].aggregate([{ \\\$out: { db: '${DST_DB}', coll: name } }]);
    print('Copied: ' + name);
  });
"

# ---------------------------------------------------------------------------
# 4. Recreate indexes
# ---------------------------------------------------------------------------
info "Recreating indexes in '${DST_DB}'..."

mongosh_eval admin "
  const src = db.getSiblingDB('${SRC_DB}');
  const dst = db.getSiblingDB('${DST_DB}');
  src.getCollectionNames().forEach(function(col) {
    src[col].getIndexes().forEach(function(idx) {
      if (idx.name === '_id_') return;
      const opts = { name: idx.name };
      if (idx.unique)                        opts.unique = true;
      if (idx.sparse)                        opts.sparse = true;
      if (idx.expireAfterSeconds !== undefined) opts.expireAfterSeconds = idx.expireAfterSeconds;
      try {
        dst[col].createIndex(idx.key, opts);
        print('Index: ' + col + '.' + idx.name);
      } catch(e) {
        print('Skipped index ' + idx.name + ' on ' + col + ': ' + e.message);
      }
    });
  });
"

# ---------------------------------------------------------------------------
# 5. Verify document counts
# ---------------------------------------------------------------------------
info "Verifying document counts..."

MISMATCH=0
IFS=',' read -ra COLS <<< "$SRC_COLLECTIONS"
for col in "${COLS[@]}"; do
    [ -z "$col" ] && continue
    SRC_N=$(mongosh_eval "$SRC_DB" "print(db['${col}'].countDocuments())")
    DST_N=$(mongosh_eval "$DST_DB" "print(db['${col}'].countDocuments())")
    if [ "$SRC_N" = "$DST_N" ]; then
        info "  ${col}: ${SRC_N} docs OK"
    else
        warn "  ${col}: src=${SRC_N} dst=${DST_N} MISMATCH"
        MISMATCH=1
    fi
done

[ "$MISMATCH" -eq 1 ] && die "Count mismatch — source database NOT dropped. Investigate and re-run."

# ---------------------------------------------------------------------------
# 6. Optionally drop source database
# ---------------------------------------------------------------------------
if [ "$DROP_SRC" = "true" ]; then
    info "Dropping source database '${SRC_DB}'..."
    mongosh_eval admin "db.getSiblingDB('${SRC_DB}').dropDatabase(); print('Dropped.');"
    info "Dropped '${SRC_DB}'."
else
    warn "Source database '${SRC_DB}' kept. Set DROP_SRC=true to drop it automatically."
fi

info "Migration complete."