param(
    [Parameter(Mandatory=$true)]
    [string]$SqlInstance,
    
    [Parameter(Mandatory=$false)]
    [string]$Directory,
    
    [Parameter(Mandatory=$false)]
    [switch]$Force
)

# backup.ps1
#
# TODO: Parallelize backups for multiple DBs in the instance

# Import SQL Server PowerShell module
try {
    # Try to import the newer SqlServer module first
    if (Get-Module -ListAvailable -Name SqlServer) {
        Import-Module SqlServer -ErrorAction Stop
        Write-Host "INFO: SqlServer PowerShell module loaded successfully."
    } 
    # Fall back to older SQLPS module if available
    elseif (Get-Module -ListAvailable -Name SQLPS) {
        Import-Module SQLPS -ErrorAction Stop
        Write-Host "INFO: SQLPS PowerShell module loaded successfully."
    }
    else {
        throw "No SQL Server PowerShell module found"
    }
    
    # Verify Invoke-Sqlcmd is available
    if (-not (Get-Command Invoke-Sqlcmd -ErrorAction SilentlyContinue)) {
        throw "Invoke-Sqlcmd command not available"
    }
}
catch {
    Write-Host "ERROR: Failed to import SQL Server PowerShell module. Please install it using: Install-Module -Name SqlServer -AllowClobber"
    Write-Host "ERROR: $($_.Exception.Message)"
    exit 1
}

$instanceName = $SqlInstance.Split('\')[1]

# Use provided directory parameter or default to instance-based path
if ($Directory) {
    $directory = $Directory
    Write-Host "INFO: Using provided directory: $directory"
} else {
    $directory = "C:\Rubrik\$instanceName"
    Write-Host "INFO: Using default directory: $directory"
}

$fullBackupDay = 'Thursday'
$fullBackupOverdueDays = 7  # Force full backup if last full backup is older than this many days
$checkCluster = $false
#$logFile = "C:\Rubrik\backup-$instanceName.log"
$logFile = "H:\Backup\backup-$instanceName.log"

$fullFlag = $directory + "\last_full.flag"
$diffFlag = $directory + "\last_diff.flag"
$today = (Get-Date).Date

function FlagTakenToday($flagPath) {
    if (Test-Path $flagPath) {
        $flagDate = (Get-Content $flagPath | Out-String).Trim()
        return ($flagDate -eq $today.ToString("yyyy-MM-dd"))
    }
    return $false
}

function GetLastFullBackupDate($flagPath) {
    if (Test-Path $flagPath) {
        $flagDate = (Get-Content $flagPath | Out-String).Trim()
        try {
            return [DateTime]::ParseExact($flagDate, "yyyy-MM-dd", $null)
        }
        catch {
            Write-Log "WARNING: Could not parse last full backup date from flag file: $flagDate"
            return $null
        }
    }
    return $null
}

function IsFullBackupOverdue($flagPath, $overdueDays) {
    $lastFullDate = GetLastFullBackupDate $flagPath
    if ($null -eq $lastFullDate) {
        Write-Log "WARNING: No last full backup date found. Full backup is considered overdue."
        return $true
    }
    
    $daysSinceLastFull = ($today - $lastFullDate).Days
    $isOverdue = $daysSinceLastFull -gt $overdueDays
    
    Write-Log "INFO: Last full backup was $daysSinceLastFull days ago on $($lastFullDate.ToString('yyyy-MM-dd')). Overdue threshold: $overdueDays days."
    
    return $isOverdue
}

function Write-Log($message) {
    $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    $logEntry = "$timestamp $message"
    Add-Content -Path $logFile -Value $logEntry
    Write-Host $logEntry
}

# Check if directory exists and is a symbolic link (unless -Force is specified)
if (-not (Test-Path $directory)) {
    Write-Log "ERROR: Directory '$directory' does not exist. Exiting script."
    exit 1
}

if (-not $Force) {
    $directoryInfo = Get-Item $directory
    if (-not ($directoryInfo.Attributes -band [System.IO.FileAttributes]::ReparsePoint)) {
        Write-Log "ERROR: Directory '$directory' is not a symbolic link. Exiting script."
        exit 1
    }
    Write-Log "INFO: Directory '$directory' exists and is a symbolic link. Target: $($directoryInfo.Target). Proceeding."
} else {
    Write-Log "INFO: Force parameter specified. Skipping symbolic link check for directory '$directory'."
}

if ($checkCluster) {
    # Check if SQL instance is running locally
    $localNode = $env:COMPUTERNAME
    
    $clusterInstance = Get-ClusterResource | Where-Object { $_.ResourceType -eq "SQL Server" -and $_.Name -eq "SQL Server ($instanceName)" }
    if ($clusterInstance) {
        $ownerNode = $clusterInstance.OwnerNode.Name
        if ($ownerNode -ne $localNode) {
            Write-Log "SQL instance '$SqlInstance' is not running on local node '$localNode'. Exiting script."
            exit 1
        } else {
            Write-Log "SQL instance '$SqlInstance' is running on local node '$localNode'. Proceeding."
        }
    } else {
        Write-Log "ERROR: SQL instance '$SqlInstance' not found in cluster resources."
        exit 1
    }
} else {
    Write-Log "INFO: Cluster check is disabled. Proceeding without verification."
}

# Check if full backup is overdue regardless of the day
$isFullBackupOverdue = IsFullBackupOverdue $fullFlag $fullBackupOverdueDays

if ((Get-Date).DayOfWeek -eq $fullBackupDay) {
    if (-not (FlagTakenToday $fullFlag)) {
        $backupType = "FULL"
        $cleanupTime = 168
        Set-Content $fullFlag $today.ToString("yyyy-MM-dd")
        Write-Log "Selected FULL backup (scheduled day). Flag updated."
    } else {
        $backupType = "LOG"
        $cleanupTime = 24
        Write-Log "FULL backup already taken today. Selected LOG backup."
    }
} elseif ($isFullBackupOverdue) {
    if (-not (FlagTakenToday $fullFlag)) {
        $backupType = "FULL"
        $cleanupTime = 168
        Set-Content $fullFlag $today.ToString("yyyy-MM-dd")
        Write-Log "Selected FULL backup (overdue - forcing full backup). Flag updated."
    } else {
        $backupType = "LOG"
        $cleanupTime = 24
        Write-Log "FULL backup already taken today (was overdue). Selected LOG backup."
    }
} else {
    if (-not (FlagTakenToday $diffFlag)) {
        $backupType = "DIFF"
        $cleanupTime = 168
        Set-Content $diffFlag $today.ToString("yyyy-MM-dd")
        Write-Log "Selected DIFF backup. Flag updated."
    } else {
        $backupType = "LOG"
        $cleanupTime = 24
        Write-Log "DIFF backup already taken today. Selected LOG backup."
    }
}

$query = "EXECUTE [dbo].[DatabaseBackup] @Databases = 'ALL_DATABASES', @Directory = '$directory', @BackupType = '$backupType', @Verify = 'N', @CleanupTime = $cleanupTime, @CheckSum = 'Y', @LogToTable = 'Y'"
Write-Log "Executing backup type: $backupType"
Write-Log "SQL Query: $query"

try {
    # Execute the backup using PowerShell SQL module with better error handling
    # Capture verbose output from Ola H scripts
    $infoMessages = @()
    
    # Create event handlers to capture SQL Server messages
    $connection = New-Object System.Data.SqlClient.SqlConnection
    $connection.ConnectionString = "Server=$SqlInstance;Integrated Security=true;Connection Timeout=30"
    
    # Event handler for informational messages (PRINT statements)
    $connection.add_InfoMessage({
        param($sqlSender, $e)
        $message = $e.Message
        if ($message -and $message.Trim() -ne "") {
            $script:infoMessages += $message
            Write-Log "SQL INFO: $message"
        }
    })
    
    try {
        $connection.Open()
        
        $command = New-Object System.Data.SqlClient.SqlCommand
        $command.Connection = $connection
        $command.CommandText = $query
        $command.CommandTimeout = 0  # No timeout for backup operations
        
        Write-Log "Executing SQL command with message capture..."
        
        # Execute and capture any result sets
        $reader = $command.ExecuteReader()
        
        # Process any result sets
        while ($reader.Read()) {
            $rowData = @()
            for ($i = 0; $i -lt $reader.FieldCount; $i++) {
                $rowData += "$($reader.GetName($i)): $($reader.GetValue($i))"
            }
            if ($rowData.Count -gt 0) {
                Write-Log "SQL RESULT: $($rowData -join ', ')"
            }
        }
        
        $reader.Close()
    }
    finally {
        if ($connection.State -eq [System.Data.ConnectionState]::Open) {
            $connection.Close()
        }
        $connection.Dispose()
    }
    
    Write-Log "$backupType Backup execution completed successfully."
    Write-Log "Total informational messages captured: $($infoMessages.Count)"
}
catch {
    Write-Log "ERROR: Backup execution failed with exception: $($_.Exception.Message)"
    
    # Log additional SQL Server error details if available
    if ($_.Exception.InnerException) {
        Write-Log "ERROR: Inner Exception: $($_.Exception.InnerException.Message)"
    }
    
    # Check for SQL Server specific errors
    if ($_.Exception -is [System.Data.SqlClient.SqlException]) {
        Write-Log "ERROR: SQL Server Error Details:"
        foreach ($sqlError in $_.Exception.Errors) {
            Write-Log "ERROR: Severity: $($sqlError.Class), State: $($sqlError.State), Number: $($sqlError.Number)"
            Write-Log "ERROR: Message: $($sqlError.Message)"
            if ($sqlError.Procedure) {
                Write-Log "ERROR: Procedure: $($sqlError.Procedure), Line: $($sqlError.LineNumber)"
            }
        }
    }
    
    # Clean up connection if it exists
    if ($connection -and $connection.State -eq [System.Data.ConnectionState]::Open) {
        $connection.Close()
        $connection.Dispose()
    }
    
    exit 1
}