#!/bin/bash
#
# Business Central SaaS Automated Backup Script
# Extracts BC data via API, encrypts, and uploads to S3 with immutability
#

set -euo pipefail

# Script directory
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
CONFIG_FILE="${SCRIPT_DIR}/bc-backup.conf"
LOG_DIR="${SCRIPT_DIR}/logs"
WORK_DIR="${SCRIPT_DIR}/temp"

# Ensure log directory exists
mkdir -p "${LOG_DIR}"
mkdir -p "${WORK_DIR}"

# Logging function
log() {
    echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*" | tee -a "${LOG_DIR}/backup.log"
}

log_error() {
    echo "[$(date '+%Y-%m-%d %H:%M:%S')] ERROR: $*" | tee -a "${LOG_DIR}/backup.log" >&2
}

# Load configuration
if [[ ! -f "${CONFIG_FILE}" ]]; then
    log_error "Configuration file not found: ${CONFIG_FILE}"
    exit 1
fi

source "${CONFIG_FILE}"

# Validate required configuration
required_vars=(
    "AZURE_TENANT_ID"
    "AZURE_CLIENT_ID"
    "AZURE_CLIENT_SECRET"
    "BC_ENVIRONMENT_NAME"
    "ENCRYPTION_PASSPHRASE"
    "S3_BUCKET"
    "S3_ENDPOINT"
    "AWS_ACCESS_KEY_ID"
    "AWS_SECRET_ACCESS_KEY"
)

for var in "${required_vars[@]}"; do
    if [[ -z "${!var:-}" ]]; then
        log_error "Required configuration variable not set: ${var}"
        exit 1
    fi
done

# Set defaults
RETENTION_DAYS="${RETENTION_DAYS:-30}"
S3_TOOL="${S3_TOOL:-awscli}"
MAX_RETRIES="${MAX_RETRIES:-3}"
CLEANUP_LOCAL="${CLEANUP_LOCAL:-true}"

log "========================================="
log "Starting Business Central backup process"
log "========================================="
log "Environment: ${BC_ENVIRONMENT_NAME}"
log "S3 Bucket: ${S3_BUCKET}"
log "Retention: ${RETENTION_DAYS} days"

# Generate timestamp for backup filename
TIMESTAMP=$(date '+%Y%m%d_%H%M%S')
BACKUP_FILENAME="bc_backup_${BC_ENVIRONMENT_NAME}_${TIMESTAMP}"

# Step 1: Extract data using PowerShell script (BC API v2.0)
log "Step 1: Extracting data via BC API v2.0"

export AZURE_TENANT_ID
export AZURE_CLIENT_ID
export AZURE_CLIENT_SECRET
export BC_ENVIRONMENT_NAME
export BC_COMPANY_NAME="${BC_COMPANY_NAME:-}"
export WORK_DIR

EXPORT_DIR="${WORK_DIR}/${BACKUP_FILENAME}"

if ! pwsh -File "${SCRIPT_DIR}/bc-export.ps1" -OutputPath "${EXPORT_DIR}"; then
    log_error "Data export failed"
    exit 1
fi

if [[ ! -d "${EXPORT_DIR}" ]]; then
    log_error "Export directory not found: ${EXPORT_DIR}"
    exit 1
fi

# Create tar.gz archive from the export directory
ARCHIVE_FILE="${WORK_DIR}/${BACKUP_FILENAME}.tar.gz"
log "Creating archive: ${ARCHIVE_FILE}"

tar -czf "${ARCHIVE_FILE}" -C "${WORK_DIR}" "${BACKUP_FILENAME}"

ARCHIVE_SIZE=$(du -h "${ARCHIVE_FILE}" | cut -f1)
log "Data export completed successfully (${ARCHIVE_SIZE})"

# Remove export directory
if [[ "${CLEANUP_LOCAL}" == "true" ]]; then
    rm -rf "${EXPORT_DIR}"
    log "Removed export directory"
fi

# Step 2: Encrypt the backup
log "Step 2: Encrypting backup file with GPG"

ENCRYPTED_FILE="${ARCHIVE_FILE}.gpg"

if ! echo "${ENCRYPTION_PASSPHRASE}" | gpg \
    --batch \
    --yes \
    --passphrase-fd 0 \
    --symmetric \
    --cipher-algo AES256 \
    --compress-algo none \
    --output "${ENCRYPTED_FILE}" \
    "${ARCHIVE_FILE}"; then
    log_error "Encryption failed"
    exit 1
fi

ENCRYPTED_SIZE=$(du -h "${ENCRYPTED_FILE}" | cut -f1)
log "Encryption completed successfully (${ENCRYPTED_SIZE})"

# Remove unencrypted archive
if [[ "${CLEANUP_LOCAL}" == "true" ]]; then
    rm -f "${ARCHIVE_FILE}"
    log "Removed unencrypted archive"
fi

# Step 3: Upload to S3 with object lock
log "Step 3: Uploading encrypted backup to S3"

S3_KEY="backups/${BACKUP_FILENAME}.tar.gz.gpg"
S3_URI="s3://${S3_BUCKET}/${S3_KEY}"

# Calculate retention date
if [[ "$OSTYPE" == "darwin"* ]]; then
    # macOS date command
    RETENTION_DATE=$(date -u -v+${RETENTION_DAYS}d '+%Y-%m-%dT%H:%M:%S')
else
    # Linux date command
    RETENTION_DATE=$(date -u -d "+${RETENTION_DAYS} days" '+%Y-%m-%dT%H:%M:%S')
fi

upload_success=false

if [[ "${S3_TOOL}" == "awscli" ]]; then
    log "Using AWS CLI for upload"

    # Upload with object lock retention
    if aws s3api put-object \
        --bucket "${S3_BUCKET}" \
        --key "${S3_KEY}" \
        --body "${ENCRYPTED_FILE}" \
        --endpoint-url "${S3_ENDPOINT}" \
        --object-lock-mode COMPLIANCE \
        --object-lock-retain-until-date "${RETENTION_DATE}Z" \
        --metadata "backup-timestamp=${TIMESTAMP},environment=${BC_ENVIRONMENT_NAME},encrypted=true,type=api-extract"; then
        upload_success=true
    fi

elif [[ "${S3_TOOL}" == "s3cmd" ]]; then
    log "Using s3cmd for upload"

    # Upload file first
    if s3cmd put \
        --host="${S3_ENDPOINT#*://}" \
        --host-bucket="${S3_ENDPOINT#*://}" \
        "${ENCRYPTED_FILE}" \
        "${S3_URI}"; then

        log "File uploaded, attempting to set object lock retention"
        # Note: s3cmd may not support object lock natively
        # Fallback to aws cli for setting retention if available
        if command -v aws &> /dev/null; then
            aws s3api put-object-retention \
                --bucket "${S3_BUCKET}" \
                --key "${S3_KEY}" \
                --endpoint-url "${S3_ENDPOINT}" \
                --retention Mode=COMPLIANCE,RetainUntilDate="${RETENTION_DATE}Z" || \
                log_error "Warning: Could not set object lock retention via AWS CLI"
        else
            log_error "Warning: s3cmd doesn't support object lock. Install aws-cli for full functionality"
        fi
        upload_success=true
    fi
else
    log_error "Invalid S3_TOOL: ${S3_TOOL}. Must be 'awscli' or 's3cmd'"
    exit 1
fi

if [[ "${upload_success}" == "true" ]]; then
    log "Upload completed successfully: ${S3_URI}"
    log "Object lock retention until: ${RETENTION_DATE}Z"
else
    log_error "Upload failed"
    exit 1
fi

# Step 4: Verify upload
log "Step 4: Verifying upload"

if [[ "${S3_TOOL}" == "awscli" ]]; then
    if aws s3api head-object \
        --bucket "${S3_BUCKET}" \
        --key "${S3_KEY}" \
        --endpoint-url "${S3_ENDPOINT}" > /dev/null 2>&1; then
        log "Upload verification successful"
    else
        log_error "Upload verification failed"
        exit 1
    fi
elif [[ "${S3_TOOL}" == "s3cmd" ]]; then
    if s3cmd info "${S3_URI}" --host="${S3_ENDPOINT#*://}" > /dev/null 2>&1; then
        log "Upload verification successful"
    else
        log_error "Upload verification failed"
        exit 1
    fi
fi

# Step 5: Cleanup
if [[ "${CLEANUP_LOCAL}" == "true" ]]; then
    log "Step 5: Cleaning up local files"
    rm -f "${ENCRYPTED_FILE}"
    log "Local encrypted file removed"
else
    log "Step 5: Skipping cleanup (CLEANUP_LOCAL=false)"
    log "Encrypted backup retained at: ${ENCRYPTED_FILE}"
fi

# Log rotation - keep last 30 days of logs
find "${LOG_DIR}" -name "backup.log.*" -mtime +30 -delete 2>/dev/null || true

log "========================================="
log "Backup completed successfully"
log "Backup file: ${S3_KEY}"
log "Size: ${ENCRYPTED_SIZE}"
log "========================================="

exit 0