#!/usr/bin/env pwsh
#
# Business Central Data Export via BC API v2.0
# Authenticates to Azure AD and extracts critical business data as JSON
#

param(
    [Parameter(Mandatory=$true)]
    [string]$OutputPath
)

# Get configuration from environment variables
$tenantId = $env:AZURE_TENANT_ID
$clientId = $env:AZURE_CLIENT_ID
$clientSecret = $env:AZURE_CLIENT_SECRET
$environmentName = $env:BC_ENVIRONMENT_NAME
$bcCompanyName = $env:BC_COMPANY_NAME  # optional: filter to specific company

$baseUrl = "https://api.businesscentral.dynamics.com/v2.0/$tenantId/$environmentName/api/v2.0"

# Standalone entities to extract
$entities = @(
    "accounts",
    "customers",
    "vendors",
    "items",
    "generalLedgerEntries",
    "bankAccounts",
    "employees",
    "dimensions",
    "dimensionValues",
    "currencies",
    "paymentTerms",
    "paymentMethods",
    "journals",
    "countriesRegions"
)

# Document entities with line items
# Lines cannot be queried standalone; they require a parent document ID
# We fetch documents in small batches with $expand to include lines
$documentEntities = @{
    "salesInvoices"     = "salesInvoiceLines"
    "salesOrders"       = "salesOrderLines"
    "salesCreditMemos"  = "salesCreditMemoLines"
    "purchaseInvoices"  = "purchaseInvoiceLines"
    "purchaseOrders"    = "purchaseOrderLines"
}

# Page size for $expand queries - kept small to avoid timeouts/OOM on large datasets
$expandPageSize = 50

# Token management
$script:currentToken = $null
$script:tokenExpiry = [datetime]::MinValue

function Write-Log {
    param([string]$Message, [string]$Level = "INFO")
    $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    Write-Host "[$timestamp] [$Level] $Message"
}

function Get-AzureADToken {
    Write-Log "Authenticating to Azure AD..."

    $tokenUrl = "https://login.microsoftonline.com/$tenantId/oauth2/v2.0/token"

    $body = @{
        client_id     = $clientId
        client_secret = $clientSecret
        scope         = "https://api.businesscentral.dynamics.com/.default"
        grant_type    = "client_credentials"
    }

    try {
        $response = Invoke-RestMethod -Uri $tokenUrl -Method Post -Body $body -ContentType "application/x-www-form-urlencoded"
        $script:currentToken = $response.access_token
        # Refresh 5 minutes before actual expiry (tokens typically last 60-90 min)
        $script:tokenExpiry = (Get-Date).AddSeconds($response.expires_in - 300)
        Write-Log "Successfully authenticated to Azure AD (expires in $($response.expires_in)s)"
        return $script:currentToken
    }
    catch {
        Write-Log "Failed to authenticate: $_" "ERROR"
        throw
    }
}

function Get-ValidToken {
    if ($null -eq $script:currentToken -or (Get-Date) -ge $script:tokenExpiry) {
        Write-Log "Token expired or missing, refreshing..."
        Get-AzureADToken | Out-Null
    }
    return $script:currentToken
}

function Get-BCData {
    param(
        [string]$Url
    )

    $token = Get-ValidToken
    $headers = @{
        "Authorization" = "Bearer $token"
        "Accept"        = "application/json"
    }

    $allRecords = @()

    $currentUrl = $Url
    while ($currentUrl) {
        try {
            $response = Invoke-RestMethod -Uri $currentUrl -Method Get -Headers $headers -TimeoutSec 300
        }
        catch {
            Write-Log "API request failed for $currentUrl : $_" "ERROR"
            throw
        }

        if ($response.value) {
            $allRecords += $response.value
        }

        # Handle OData pagination
        $currentUrl = $response.'@odata.nextLink'
    }

    return $allRecords
}

function Get-Companies {
    Write-Log "Fetching companies..."
    $companiesUrl = "$baseUrl/companies"
    $companies = Get-BCData -Url $companiesUrl
    Write-Log "Found $($companies.Count) company/companies"
    return $companies
}

function Export-EntityData {
    param(
        [string]$CompanyId,
        [string]$CompanyName,
        [string]$EntityName,
        [string]$OutputDir
    )

    $entityUrl = "$baseUrl/companies($CompanyId)/$EntityName"

    Write-Log "  Exporting $EntityName..."

    try {
        $data = Get-BCData -Url $entityUrl
        $count = 0
        if ($data) { $count = $data.Count }

        $outputFile = Join-Path $OutputDir "$EntityName.json"
        $data | ConvertTo-Json -Depth 10 | Out-File -FilePath $outputFile -Encoding utf8

        Write-Log "  $EntityName : $count records"
        return $count
    }
    catch {
        Write-Log "  Failed to export ${EntityName}: $_" "WARN"
        $outputFile = Join-Path $OutputDir "$EntityName.json"
        "[]" | Out-File -FilePath $outputFile -Encoding utf8
        return 0
    }
}

function Export-DocumentWithLines {
    param(
        [string]$CompanyId,
        [string]$CompanyName,
        [string]$DocumentEntity,
        [string]$LineEntity,
        [string]$OutputDir
    )

    # Use $expand with small $top to avoid huge payloads
    # BC API will provide @odata.nextLink for subsequent pages
    $entityUrl = "$baseUrl/companies($CompanyId)/$DocumentEntity" + '?$expand=' + $LineEntity + '&$top=' + $expandPageSize

    Write-Log "  Exporting $DocumentEntity (with $LineEntity, batch size $expandPageSize)..."

    $outputFile = Join-Path $OutputDir "$DocumentEntity.jsonl"
    $docCount = 0
    $lineCount = 0
    $currentUrl = $entityUrl

    try {
        # Clear output file
        [System.IO.File]::WriteAllText($outputFile, "")

        while ($currentUrl) {
            $token = Get-ValidToken
            $headers = @{
                "Authorization" = "Bearer $token"
                "Accept"        = "application/json"
            }

            try {
                $response = Invoke-RestMethod -Uri $currentUrl -Method Get -Headers $headers -TimeoutSec 300
            }
            catch {
                Write-Log "  API request failed at doc #$docCount : $_" "ERROR"
                throw
            }

            if ($response.value) {
                foreach ($doc in $response.value) {
                    $lines = 0
                    if ($doc.$LineEntity) {
                        $lines = $doc.$LineEntity.Count
                    }
                    $lineCount += $lines
                    $docCount++

                    # Write each document immediately to disk (JSONL: one JSON object per line)
                    $jsonLine = $doc | ConvertTo-Json -Depth 10 -Compress
                    [System.IO.File]::AppendAllText($outputFile, $jsonLine + "`n")
                }
            }

            Write-Log "    Progress: $docCount documents, $lineCount lines"

            # Next page
            $currentUrl = $response.'@odata.nextLink'
        }

        Write-Log "  $DocumentEntity : $docCount documents, $lineCount lines (complete)"
        return ($docCount + $lineCount)
    }
    catch {
        Write-Log "  Failed to export ${DocumentEntity} with lines at doc #$docCount : $_" "WARN"
        return 0
    }
}

# Main execution
try {
    Write-Log "========================================="
    Write-Log "BC Data Export Script (API v2.0)"
    Write-Log "========================================="
    Write-Log "Environment: $environmentName"
    Write-Log "Output Path: $OutputPath"
    Write-Log "Entities to extract: $($entities.Count + $documentEntities.Count) ($($documentEntities.Count) with line items)"

    # Create output directory
    $exportDir = $OutputPath
    if (-not (Test-Path $exportDir)) {
        New-Item -ItemType Directory -Path $exportDir -Force | Out-Null
    }

    # Step 1: Get Azure AD token
    Get-AzureADToken | Out-Null

    # Step 2: Get companies
    $companies = Get-Companies

    if ($companies.Count -eq 0) {
        Write-Log "No companies found in environment $environmentName" "ERROR"
        exit 1
    }

    # Save companies list
    $companies | ConvertTo-Json -Depth 10 | Out-File -FilePath (Join-Path $exportDir "companies.json") -Encoding utf8

    # Filter to specific company if configured
    $targetCompanies = $companies
    if ($bcCompanyName) {
        $targetCompanies = $companies | Where-Object { $_.name -eq $bcCompanyName -or $_.displayName -eq $bcCompanyName }
        if ($targetCompanies.Count -eq 0) {
            Write-Log "Company '$bcCompanyName' not found. Available: $($companies.name -join ', ')" "ERROR"
            exit 1
        }
        Write-Log "Filtering to company: $bcCompanyName"
    }

    $totalRecords = 0
    $totalEntities = 0
    $failedEntities = @()

    # Step 3: Export data for each company
    foreach ($company in $targetCompanies) {
        $companyName = $company.name
        $companyId = $company.id

        Write-Log "-----------------------------------------"
        Write-Log "Exporting company: $companyName ($companyId)"

        # Create company directory (sanitize name for filesystem)
        $safeName = $companyName -replace '[\\/:*?"<>|]', '_'
        $companyDir = Join-Path $exportDir $safeName
        if (-not (Test-Path $companyDir)) {
            New-Item -ItemType Directory -Path $companyDir -Force | Out-Null
        }

        # Export standalone entities
        foreach ($entity in $entities) {
            $count = Export-EntityData `
                -CompanyId $companyId `
                -CompanyName $companyName `
                -EntityName $entity `
                -OutputDir $companyDir

            $totalRecords += $count
            $totalEntities++

            if ($count -eq 0) {
                $failedEntities += "$companyName/$entity"
            }
        }

        # Export document entities with their line items
        # Uses small batches + streaming to disk to handle large datasets
        foreach ($docEntity in $documentEntities.Keys) {
            $lineEntity = $documentEntities[$docEntity]

            $count = Export-DocumentWithLines `
                -CompanyId $companyId `
                -CompanyName $companyName `
                -DocumentEntity $docEntity `
                -LineEntity $lineEntity `
                -OutputDir $companyDir

            $totalRecords += $count
            $totalEntities++

            if ($count -eq 0) {
                $failedEntities += "$companyName/$docEntity"
            }
        }
    }

    # Save export metadata
    $metadata = @{
        exportDate       = (Get-Date -Format "yyyy-MM-dd HH:mm:ss UTC" -AsUTC)
        environment      = $environmentName
        companies        = @($targetCompanies | ForEach-Object { $_.name })
        entitiesExported = $totalEntities
        totalRecords     = $totalRecords
        failedEntities   = $failedEntities
    }
    $metadata | ConvertTo-Json -Depth 5 | Out-File -FilePath (Join-Path $exportDir "export-metadata.json") -Encoding utf8

    Write-Log "========================================="
    Write-Log "Export completed"
    Write-Log "Companies: $($targetCompanies.Count)"
    Write-Log "Entities: $totalEntities"
    Write-Log "Total records: $totalRecords"
    if ($failedEntities.Count -gt 0) {
        Write-Log "Failed/empty: $($failedEntities.Count) entities" "WARN"
    }
    Write-Log "========================================="
    exit 0
}
catch {
    Write-Log "Unexpected error: $_" "ERROR"
    Write-Log "Stack trace: $($_.ScriptStackTrace)" "ERROR"
    exit 1
}