[CmdletBinding()]
param(
    [switch]$Check
)

Set-StrictMode -Version Latest
$ErrorActionPreference = "Stop"

# Pinned protoc toolchain version used to generate the committed client descriptor set.
# See docs/ToolchainLinks.md. Generating (committing) the canonical artifact must use this
# exact version so the checked-in bytes are reproducible. The -Check comparison is made
# tolerant of protoc-version encoding drift (chiefly source_code_info, see IPC-20) by
# normalizing both the committed and the freshly built descriptor through the *same* protoc
# with source info stripped, so it does not false-fail across protoc releases.
$PinnedProtocVersion = "34.1"

$repoRoot = Resolve-Path (Join-Path $PSScriptRoot "..")
$protoRoot = Join-Path $repoRoot "src/ZB.MOM.WW.MxGateway.Contracts/Protos"
$manifestPath = Join-Path $repoRoot "clients/proto/proto-inputs.json"
$descriptorPath = Join-Path $repoRoot "clients/proto/descriptors/mxaccessgw-client-v1.protoset"
$protoFiles = @("mxaccess_gateway.proto", "mxaccess_worker.proto", "galaxy_repository.proto")

function Resolve-Protoc {
    # Prefer protoc on PATH (protoc on Linux/macOS, protoc.exe on Windows), then fall back to
    # the documented winget install location on Windows.
    foreach ($name in @("protoc", "protoc.exe")) {
        $pathCommand = Get-Command $name -ErrorAction SilentlyContinue
        if ($null -ne $pathCommand) {
            return $pathCommand.Source
        }
    }

    if ($env:LOCALAPPDATA) {
        $documentedPath = Join-Path $env:LOCALAPPDATA "Microsoft/WinGet/Packages/Google.Protobuf_Microsoft.Winget.Source_8wekyb3d8bbwe/bin/protoc.exe"
        if (Test-Path $documentedPath) {
            return $documentedPath
        }
    }

    throw "Could not find protoc on PATH. See docs/ToolchainLinks.md for the documented protobuf toolchain (protoc $PinnedProtocVersion)."
}

function Get-ProtocVersion {
    param([string]$Protoc)

    # `protoc --version` prints e.g. "libprotoc 34.1".
    $raw = (& $Protoc --version) | Select-Object -First 1
    return ($raw -replace '^libprotoc\s+', '').Trim()
}

function Ensure-Directory {
    param([string]$Path)

    if (-not (Test-Path $Path)) {
        New-Item -ItemType Directory -Path $Path | Out-Null
    }
}

function New-SourceInfoFreeDescriptor {
    # Re-emits an existing descriptor set with source_code_info stripped, by round-tripping it
    # through protoc with --descriptor_set_in and *without* --include_source_info. Because both
    # the committed and freshly built descriptors are normalized through the same protoc binary,
    # any protoc-version-specific encoding cancels out and the byte comparison is stable.
    param(
        [string]$Protoc,
        [string]$InputDescriptor,
        [string]$OutputDescriptor
    )

    & $Protoc `
        "--descriptor_set_in=$InputDescriptor" `
        "--include_imports" `
        "--descriptor_set_out=$OutputDescriptor" `
        @protoFiles

    if ($LASTEXITCODE -ne 0) {
        throw "protoc normalization (--descriptor_set_in) failed with exit code $LASTEXITCODE."
    }
}

function Test-FileBytesEqual {
    param(
        [string]$ExpectedPath,
        [string]$ActualPath
    )

    if (-not (Test-Path $ExpectedPath)) {
        return $false
    }

    $expected = [System.IO.File]::ReadAllBytes($ExpectedPath)
    $actual = [System.IO.File]::ReadAllBytes($ActualPath)
    if ($expected.Length -ne $actual.Length) {
        return $false
    }

    for ($index = 0; $index -lt $expected.Length; $index++) {
        if ($expected[$index] -ne $actual[$index]) {
            return $false
        }
    }

    return $true
}

$manifest = Get-Content -Raw $manifestPath | ConvertFrom-Json

Ensure-Directory (Split-Path $descriptorPath -Parent)
foreach ($output in $manifest.generatedOutputs.PSObject.Properties.Value) {
    Ensure-Directory (Join-Path $repoRoot $output)
}

$protoc = Resolve-Protoc
$protocVersion = Get-ProtocVersion $protoc

if ($Check) {
    # Version drift no longer produces a false "stale" failure: the comparison is normalized
    # below. A mismatch is surfaced as a warning so it is visible without blocking the gate.
    if ($protocVersion -ne $PinnedProtocVersion) {
        Write-Warning "protoc version '$protocVersion' differs from the pinned '$PinnedProtocVersion'. The freshness comparison is normalized and tolerant of this, but regeneration must use the pinned version (see docs/ClientProtoGeneration.md)."
    }

    $freshDescriptor = Join-Path ([System.IO.Path]::GetTempPath()) ("mxaccessgw-client-v1-fresh-" + [System.Guid]::NewGuid().ToString("N") + ".protoset")
    $committedNormalized = Join-Path ([System.IO.Path]::GetTempPath()) ("mxaccessgw-client-v1-committed-" + [System.Guid]::NewGuid().ToString("N") + ".protoset")

    try {
        # Fresh descriptor from the current .proto sources, source info omitted (already normalized).
        & $protoc `
            "--proto_path=$protoRoot" `
            "--include_imports" `
            "--descriptor_set_out=$freshDescriptor" `
            @protoFiles

        if ($LASTEXITCODE -ne 0) {
            throw "protoc failed with exit code $LASTEXITCODE."
        }

        if (-not (Test-Path $descriptorPath)) {
            throw "Committed descriptor '$descriptorPath' does not exist. Run scripts/publish-client-proto-inputs.ps1 to create it."
        }

        # Normalize the committed descriptor (which carries source info) through the same protoc.
        New-SourceInfoFreeDescriptor -Protoc $protoc -InputDescriptor $descriptorPath -OutputDescriptor $committedNormalized

        if (-not (Test-FileBytesEqual -ExpectedPath $committedNormalized -ActualPath $freshDescriptor)) {
            throw "Client proto descriptor is stale. Run scripts/publish-client-proto-inputs.ps1 with the pinned protoc ($PinnedProtocVersion) and commit the updated descriptor."
        }

        Write-Host "Client proto descriptor is up to date."
    }
    finally {
        foreach ($temp in @($freshDescriptor, $committedNormalized)) {
            if (Test-Path $temp) {
                Remove-Item -LiteralPath $temp
            }
        }
    }
}
else {
    # Generating the canonical committed artifact must use the pinned protoc so the bytes are reproducible.
    if ($protocVersion -ne $PinnedProtocVersion) {
        throw "protoc version '$protocVersion' does not match the pinned toolchain version '$PinnedProtocVersion'. Install the pinned protoc (see docs/ToolchainLinks.md) before regenerating the committed descriptor, or run with -Check to only verify freshness."
    }

    & $protoc `
        "--proto_path=$protoRoot" `
        "--include_imports" `
        "--include_source_info" `
        "--descriptor_set_out=$descriptorPath" `
        @protoFiles

    if ($LASTEXITCODE -ne 0) {
        throw "protoc failed with exit code $LASTEXITCODE."
    }

    Write-Host "Wrote client proto descriptor to $descriptorPath (protoc $protocVersion)."
}