param(
    [Parameter(Mandatory = $true)]
    [string] $SdfPath,

    [Parameter(Mandatory = $true)]
    [string] $OutFile,

    [string] $Password = '',

    [string] $SqlCeDll = ''
)

$ErrorActionPreference = 'Stop'

function Find-SqlCeDll([string] $preferred) {
    if ($preferred -and (Test-Path -LiteralPath $preferred)) {
        return $preferred
    }

    $candidates = @(
        'C:\Program Files\Microsoft SQL Server Compact Edition\v4.0\Desktop\System.Data.SqlServerCe.dll',
        'C:\Program Files (x86)\Microsoft SQL Server Compact Edition\v4.0\Desktop\System.Data.SqlServerCe.dll'
    )
    foreach ($path in $candidates) {
        if (Test-Path -LiteralPath $path) {
            return $path
        }
    }

    throw 'Nenalezena knihovna System.Data.SqlServerCe.dll (SQL Server Compact 4.0).'
}

function New-ConnectionString([string] $path, [string] $password) {
    $cs = "Data Source=$path;Max Database Size=4091"
    if ($password -ne '') {
        $cs += ";Password=$password"
    }
    return $cs
}

function Read-TableOptional($connection, [string] $sql) {
    try {
        return @(Read-Table $connection $sql)
    } catch {
        return @()
    }
}

function Read-Table($connection, [string] $sql) {
    $cmd = $connection.CreateCommand()
    $cmd.CommandText = $sql
    $adapter = New-Object System.Data.SqlServerCe.SqlCeDataAdapter($cmd)
    $table = New-Object System.Data.DataTable
    [void] $adapter.Fill($table)

    $rows = New-Object System.Collections.Generic.List[object]
    foreach ($row in $table.Rows) {
        $item = [ordered] @{}
        foreach ($col in $table.Columns) {
            $value = $row[$col]
            if ($value -is [DBNull]) {
                $item[$col.ColumnName] = $null
            } elseif ($value -is [datetime]) {
                $item[$col.ColumnName] = ([datetime] $value).ToString('o')
            } else {
                $item[$col.ColumnName] = $value
            }
        }
        $rows.Add([pscustomobject] $item)
    }

    return $rows
}

function Open-Sdf([string] $path, [string] $password) {
    $cs = New-ConnectionString $path $password
    try {
        $conn = New-Object System.Data.SqlServerCe.SqlCeConnection($cs)
        $conn.Open()
        return $conn
    } catch {
        $message = $_.Exception.Message
        if ($message -notmatch 'earlier version|Upgrade') {
            throw
        }
        $engine = New-Object System.Data.SqlServerCe.SqlCeEngine($cs)
        $engine.Upgrade()
        $conn = New-Object System.Data.SqlServerCe.SqlCeConnection($cs)
        $conn.Open()
        return $conn
    }
}

if (-not (Test-Path -LiteralPath $SdfPath)) {
    throw "SDF soubor neexistuje: $SdfPath"
}

Add-Type -Path (Find-SqlCeDll $SqlCeDll)

$workDir = Split-Path -Parent $OutFile
if (-not (Test-Path -LiteralPath $workDir)) {
    New-Item -ItemType Directory -Path $workDir | Out-Null
}

$workSdf = Join-Path $workDir 'source.sdf'
Copy-Item -LiteralPath $SdfPath -Destination $workSdf -Force

$passwords = @()
if ($Password -ne '') { $passwords += $Password }
$passwords += ''

$connection = $null
$lastError = $null
foreach ($pw in $passwords) {
    try {
        $connection = Open-Sdf $workSdf $pw
        break
    } catch {
        $lastError = $_
        $connection = $null
    }
}

if (-not $connection) {
    throw "Nepodařilo se otevřít SDF databázi. $($lastError.Exception.Message)"
}

try {
    $payload = [ordered] @{
        uzivatel = @(Read-Table $connection 'SELECT * FROM UZIVATEL ORDER BY ID')
        zakaznik = @(Read-Table $connection 'SELECT * FROM ZAKAZNIK ORDER BY ID')
        faktura  = @(Read-Table $connection 'SELECT * FROM FAKTURA ORDER BY ID')
        polozka  = @(Read-Table $connection 'SELECT * FROM POLOZKA ORDER BY ID')
        platba   = @(Read-TableOptional $connection 'SELECT * FROM PLATBA ORDER BY ID')
        konfigurace = @(Read-TableOptional $connection 'SELECT ID, DATA FROM KONFIGURACE ORDER BY ID')
    }

    $json = $payload | ConvertTo-Json -Depth 6 -Compress:$false
    [System.IO.File]::WriteAllText($OutFile, $json, [System.Text.UTF8Encoding]::new($false))
} finally {
    if ($connection -and $connection.State -eq 'Open') {
        $connection.Close()
    }
}