param(
    [Parameter(Mandatory=$true)]
    [string]$SqlInstance,
    
    [Parameter(Mandatory=$false)]
    [string]$Directories,
    
    [Parameter(Mandatory=$false)]
    [int]$Jobs = 2,
    
    [Parameter(Mandatory=$false)]
    [switch]$Force
)

#
# backupmult.ps1 - Parallel database backup script using Ola Hallengren's DatabasesInParallel feature
#
# Uses Ola H's built-in parallel processing by starting multiple concurrent backup jobs
# Each job will automatically share the database load using DatabasesInParallel=Y
#

# Import SQL Server PowerShell module
try {
    if (Get-Module -ListAvailable -Name SqlServer) {
        Import-Module SqlServer -ErrorAction Stop
        Write-Host "INFO: SqlServer PowerShell module loaded successfully."
    } 
    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"
    }
    
    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 directories or default to comma-separated multi-directory setup
if ($Directories) {
    $directoryParam = $Directories
    Write-Host "INFO: Using provided directories: $directoryParam"
} else {
    $directoryParam = "C:\Rubrik\$instanceName\Dir1, C:\Rubrik\$instanceName\Dir2, C:\Rubrik\$instanceName\Dir3, C:\Rubrik\$instanceName\Dir4"
    Write-Host "INFO: Using default multi-directory setup: $directoryParam"
}

$fullBackupDay = 'Thursday'
$fullBackupOverdueDays = 7
$logFile = "C:\Rubrik\backup-multi-$instanceName.log"

# Validate job count
if ($Jobs -lt 1 -or $Jobs -gt 8) {
    Write-Host "ERROR: Jobs parameter must be between 1 and 8. Provided: $Jobs"
    exit 1
}

Write-Host "INFO: Starting $Jobs parallel backup jobs"

$today = (Get-Date).Date

function Write-Log($message, $jobId = "") {
    $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    $jobPrefix = if ($jobId) { "[JOB-$jobId] " } else { "" }
    $logEntry = "$timestamp $jobPrefix$message"
    
    # Use mutex for thread-safe logging to main log file
    $mutex = $null
    try {
        $mutex = [System.Threading.Mutex]::new($false, "BackupLogMutex")
        if ($mutex.WaitOne(5000)) {  # 5 second timeout
            Add-Content -Path $logFile -Value $logEntry -Encoding UTF8
        } else {
            Write-Warning "Could not acquire log mutex, writing to console only"
        }
    } catch {
        Write-Warning "Logging error: $($_.Exception.Message)"
    } finally {
        if ($mutex) {
            $mutex.ReleaseMutex()
            $mutex.Dispose()
        }
    }
    
    Write-Host $logEntry
}

function Get-BackupType($directoryParam) {
    # Use first directory to check flags (assuming shared flag logic across all directories)
    $firstDir = ($directoryParam -split ',')[0].Trim()
    $fullFlag = Join-Path $firstDir "last_full.flag"
    $diffFlag = Join-Path $firstDir "last_diff.flag"
    
    # Check if full backup is overdue
    $isFullBackupOverdue = $false
    if (Test-Path $fullFlag) {
        try {
            $lastFullDate = [DateTime]::ParseExact((Get-Content $fullFlag).Trim(), "yyyy-MM-dd", $null)
            $daysSinceLastFull = ($today - $lastFullDate).Days
            $isFullBackupOverdue = $daysSinceLastFull -gt $fullBackupOverdueDays
            Write-Log "INFO: Last full backup was $daysSinceLastFull days ago. Overdue threshold: $fullBackupOverdueDays days."
        }
        catch {
            $isFullBackupOverdue = $true
            Write-Log "WARNING: Could not parse last full backup date. Treating as overdue."
        }
    } else {
        $isFullBackupOverdue = $true
        Write-Log "WARNING: No last full backup date found. Treating as overdue."
    }
    
    # Determine backup type
    if ((Get-Date).DayOfWeek -eq $fullBackupDay -or $isFullBackupOverdue) {
        if (-not (Test-Path $fullFlag) -or (Get-Content $fullFlag).Trim() -ne $today.ToString("yyyy-MM-dd")) {
            # Create flag directory if it doesn't exist
            $flagDir = Split-Path $fullFlag -Parent
            if (-not (Test-Path $flagDir)) {
                New-Item -ItemType Directory -Path $flagDir -Force | Out-Null
            }
            Set-Content $fullFlag $today.ToString("yyyy-MM-dd") -Encoding UTF8
            $reason = if($isFullBackupOverdue) { "overdue" } else { "scheduled" }
            return @{ Type = "FULL"; CleanupTime = 168; Reason = $reason }
        } else {
            return @{ Type = "LOG"; CleanupTime = 24; Reason = "full already taken today" }
        }
    } else {
        if (-not (Test-Path $diffFlag) -or (Get-Content $diffFlag).Trim() -ne $today.ToString("yyyy-MM-dd")) {
            # Create flag directory if it doesn't exist
            $flagDir = Split-Path $diffFlag -Parent
            if (-not (Test-Path $flagDir)) {
                New-Item -ItemType Directory -Path $flagDir -Force | Out-Null
            }
            Set-Content $diffFlag $today.ToString("yyyy-MM-dd") -Encoding UTF8
            return @{ Type = "DIFF"; CleanupTime = 168; Reason = "differential scheduled" }
        } else {
            return @{ Type = "LOG"; CleanupTime = 24; Reason = "diff already taken today" }
        }
    }
}

# Determine backup type
$backupInfo = Get-BackupType $directoryParam
Write-Log "Selected $($backupInfo.Type) backup ($($backupInfo.Reason))"

# Build the Ola H query with DatabasesInParallel enabled
$query = @"
EXECUTE [dbo].[DatabaseBackup] 
    @Databases = 'ALL_DATABASES',
    @Directory = '$directoryParam',
    @BackupType = '$($backupInfo.Type)',
    @Verify = 'N',
    @CleanupTime = $($backupInfo.CleanupTime),
    @CheckSum = 'Y',
    @LogToTable = 'Y',
    @DatabasesInParallel = 'Y'
"@

Write-Log "SQL Query: $query"

# Function to execute backup job with message capture
function Start-BackupJob($jobId, $sqlInstance, $query, $baseLogFile) {    
    $scriptBlock = {
        param($JobId, $SqlInstance, $Query, $BaseLogFile)
        
        # Create job-specific log file path
        $jobLogFile = $BaseLogFile -replace '\.log$', "-job$JobId.log"
        
        function Write-JobLog($message) {
            $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
            $logEntry = "$timestamp [JOB-$JobId] $message"
            if ($jobLogFile -and $jobLogFile.Trim() -ne "") {
                Add-Content -Path $jobLogFile -Value $logEntry -Encoding UTF8
            }
            Write-Output $logEntry
        }
        
        try {
            Write-JobLog "Starting backup job"
            
            # Create SQL connection with message capture
            $connection = New-Object System.Data.SqlClient.SqlConnection
            $connection.ConnectionString = "Server=$SqlInstance;Integrated Security=true;Connection Timeout=30"
            
            $infoMessages = @()
            
            # 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-JobLog "SQL INFO: $message"
                }
            })
            
            try {
                $connection.Open()
                Write-JobLog "Connected to SQL Server"
                
                $command = New-Object System.Data.SqlClient.SqlCommand
                $command.Connection = $connection
                $command.CommandText = $Query
                $command.CommandTimeout = 0  # No timeout for backup operations
                
                Write-JobLog "Executing backup command..."
                
                # 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-JobLog "SQL RESULT: $($rowData -join ', ')"
                    }
                }
                
                $reader.Close()
                Write-JobLog "Backup completed successfully. Captured $($infoMessages.Count) messages."
                return @{ Success = $true; JobId = $JobId }
            }
            finally {
                if ($connection.State -eq [System.Data.ConnectionState]::Open) {
                    $connection.Close()
                }
                $connection.Dispose()
            }
        }
        catch {
            Write-JobLog "ERROR: Backup failed - $($_.Exception.Message)"
            
            # Log SQL Server specific errors
            if ($_.Exception -is [System.Data.SqlClient.SqlException]) {
                Write-JobLog "ERROR: SQL Server Error Details:"
                foreach ($sqlError in $_.Exception.Errors) {
                    Write-JobLog "ERROR: Severity: $($sqlError.Class), State: $($sqlError.State), Number: $($sqlError.Number)"
                    Write-JobLog "ERROR: Message: $($sqlError.Message)"
                    if ($sqlError.Procedure) {
                        Write-JobLog "ERROR: Procedure: $($sqlError.Procedure), Line: $($sqlError.LineNumber)"
                    }
                }
            }
            
            return @{ Success = $false; JobId = $JobId; ErrorMessage = $_.Exception.Message }
        }
    }
    
    return Start-Job -ScriptBlock $scriptBlock -ArgumentList $jobId, $sqlInstance, $query, $baseLogFile
}

# Start parallel backup jobs
Write-Log "Starting $Jobs parallel backup jobs using DatabasesInParallel feature"
[System.Collections.ArrayList]$jobList = @()

for ($i = 1; $i -le $Jobs; $i++) {
    $job = Start-BackupJob -jobId $i -sqlInstance $SqlInstance -query $query -logFile $logFile
    $null = $jobList.Add($job)
    Write-Log "Started backup job $i (Job ID: $($job.Id))"
    Start-Sleep -Milliseconds 100  # Small delay to stagger job starts
}

# Monitor jobs and capture output
Write-Log "Monitoring $($jobList.Count) backup jobs..."
$allJobsCompleted = $false
[System.Collections.ArrayList]$completedJobs = @()

while (-not $allJobsCompleted) {
    Start-Sleep -Seconds 5
    
    foreach ($job in $jobList) {
        if ($job.Id -notin $completedJobs -and $job.State -ne "Running") {
            $null = $completedJobs.Add($job.Id)
            
            if ($job.State -eq "Completed") {
                $result = Receive-Job -Job $job
                if ($result) {
                    foreach ($line in $result) {
                        Write-Host $line
                    }
                }
                Write-Log "Job $($job.Id) completed successfully"
            } else {
                $jobError = Receive-Job -Job $job
                Write-Log "ERROR: Job $($job.Id) failed with state: $($job.State)"
                if ($jobError) {
                    foreach ($line in $jobError) {
                        Write-Log "ERROR: $line"
                    }
                }
            }
            
            Remove-Job -Job $job
        }
    }
    
    $allJobsCompleted = $completedJobs.Count -eq $jobList.Count
    
    # Progress update
    $runningCount = ($jobList | Where-Object { $_.State -eq "Running" }).Count
    if ($runningCount -gt 0) {
        Write-Log "Progress: $($completedJobs.Count)/$($jobList.Count) jobs completed, $runningCount still running..."
    }
}

Write-Log "All backup jobs completed"

# Consolidate job logs into main log file
Write-Log "Consolidating job logs..."
for ($i = 1; $i -le $Jobs; $i++) {
    $jobLogFile = $logFile -replace '\.log$', "-job$i.log"
    if (Test-Path $jobLogFile) {
        try {
            $jobContent = Get-Content $jobLogFile -ErrorAction Stop
            foreach ($line in $jobContent) {
                Add-Content -Path $logFile -Value $line -Encoding UTF8
            }
            Remove-Item $jobLogFile -Force
            Write-Log "Consolidated log from job $i"
        } catch {
            Write-Log "WARNING: Could not consolidate log from job $i : $($_.Exception.Message)"
        }
    }
}

# Final status check
$failedJobs = $jobList | Where-Object { $_.State -ne "Completed" }
if ($failedJobs.Count -gt 0) {
    Write-Log "ERROR: $($failedJobs.Count) jobs failed"
    exit 1
} else {
    Write-Log "SUCCESS: All $($jobList.Count) backup jobs completed successfully"
}