try {
    Add-Type -AssemblyName System.Data
} catch {
    # Ignore if already loaded or not available in some environments
}

function Import-DBAToolBoxDependencies {
    <#
    .SYNOPSIS
        Ensures the dbatools module is available and imported.
    #>
    if (-not (Get-Module -ListAvailable dbatools)) {
        throw "The 'dbatools' module is not installed. Please install it using 'Install-Module dbatools'."
    }
    
    if (-not (Get-Module dbatools)) {
        Import-Module dbatools -ErrorAction Stop
    }
}

function Test-SQLConnection {
    <#
    .SYNOPSIS
        Tests connection to a SQL Server instance and returns basic info using native ADO.NET.
    #>
    param(
        [Parameter(Mandatory=$true)]
        [string]$ServerInstance
    )

    $connString = "Server=$ServerInstance;Database=master;Integrated Security=True;Connection Timeout=5;TrustServerCertificate=True;"
    $connection = New-Object System.Data.SqlClient.SqlConnection($connString)
    try {
        $connection.Open()
        
        # Query basic server properties
        $cmd = $connection.CreateCommand()
        $cmd.CommandText = "SELECT @@VERSION as Version, SERVERPROPERTY('Edition') as Edition, SERVERPROPERTY('MachineName') as Instance, SERVERPROPERTY('ProductVersion') as VerString"
        $reader = $cmd.ExecuteReader()
        
        if ($reader.Read()) {
            $ver = if ($reader["VerString"] -ne [System.DBNull]::Value -and $reader["VerString"] -ne $null) { $reader["VerString"].ToString() } else { "Unknown" }
            $edition = if ($reader["Edition"] -ne [System.DBNull]::Value -and $reader["Edition"] -ne $null) { $reader["Edition"].ToString() } else { "Unknown" }
            $instance = if ($reader["Instance"] -ne [System.DBNull]::Value -and $reader["Instance"] -ne $null) { $reader["Instance"].ToString() } else { "" }
            
            return @{
                Success = $true
                Instance = if ([string]::IsNullOrEmpty($instance)) { $ServerInstance } else { $instance }
                Version = $ver
                Edition = $edition
                Status = "Online"
            }
        } else {
            return @{ Success = $false; Error = "Failed to read server properties." }
        }
    } catch {
        return @{ Success = $false; Error = $_.Exception.Message }
    } finally {
        if ($null -ne $connection -and $connection.State.ToString() -eq "Open") {
            $connection.Close()
        }
    }
}

function Get-SQLDatabases {
    <#
    .SYNOPSIS
        Gets database information for a SQL Server instance using native ADO.NET.
    #>
    param(
        [Parameter(Mandatory=$true)]
        [string]$ServerInstance
    )

    $connString = "Server=$ServerInstance;Database=master;Integrated Security=True;Connection Timeout=5;TrustServerCertificate=True;"
    $connection = New-Object System.Data.SqlClient.SqlConnection($connString)
    try {
        $connection.Open()
        
        # Query databases from sys.databases joined with sys.master_files to correctly sum file sizes.
        # sys.databases does not have a "size" column. We must group and sum size from sys.master_files.
        $cmd = $connection.CreateCommand()
        $cmd.CommandText = @"
SELECT 
    d.name, 
    d.state_desc, 
    COALESCE(SUM(CAST(f.size AS FLOAT) * 8.0 / 1024.0), 0.0) as size_mb, 
    d.recovery_model_desc 
FROM sys.databases d
LEFT JOIN sys.master_files f ON d.database_id = f.database_id
GROUP BY d.name, d.state_desc, d.recovery_model_desc
"@
        
        $adapter = New-Object System.Data.SqlClient.SqlDataAdapter($cmd)
        $table = New-Object System.Data.DataTable
        $null = $adapter.Fill($table)
        
        $dbList = @()
        foreach ($row in $table.Rows) {
            $sizeVal = 0.0
            if ($row.size_mb -ne [System.DBNull]::Value -and $row.size_mb -ne $null) {
                $sizeVal = [double]$row.size_mb
            }
            
            $dbName = if ($row.name -ne [System.DBNull]::Value -and $row.name -ne $null) { $row.name.ToString() } else { "Unknown" }
            $dbStatus = if ($row.state_desc -ne [System.DBNull]::Value -and $row.state_desc -ne $null) { $row.state_desc.ToString() } else { "Unknown" }
            $dbRecovery = if ($row.recovery_model_desc -ne [System.DBNull]::Value -and $row.recovery_model_desc -ne $null) { $row.recovery_model_desc.ToString() } else { "Simple" }

            $dbList += [pscustomobject]@{
                Name = $dbName
                Status = $dbStatus
                Size = "$([Math]::Round($sizeVal, 2)) MB"
                RecoveryModel = $dbRecovery
            }
        }
        return $dbList
    } catch {
        throw "Failed to get databases: $($_.Exception.Message)"
    } finally {
        if ($null -ne $connection -and $connection.State.ToString() -eq "Open") {
            $connection.Close()
        }
    }
}

function Get-SQLErrors {
    <#
    .SYNOPSIS
        Gets SQL Server error log entries for the last hour using Get-DbaErrorLog.
    #>
    param(
        [Parameter(Mandatory=$true)]
        [string]$ServerInstance
    )

    try {
        # Calculate time (1 hour ago)
        $afterTime = (Get-Date).AddHours(-1)
        $afterString = $afterTime.ToString("yyyy-MM-dd HH:mm:ss")
        
        # Call dbatools cmdlet to fetch log entries
        $logs = Get-DbaErrorLog -SqlInstance $ServerInstance -After $afterString -LogNumber 0 -ErrorAction Stop
        
        # Clean select properties
        $result = $logs | Select-Object LogDate, Source, Text
        return $result
    } catch {
        throw "Failed to fetch SQL error log: $($_.Exception.Message)"
    }
}

Export-ModuleMember -Function Import-DBAToolBoxDependencies, Test-SQLConnection, Get-SQLDatabases, Get-SQLErrors