#load "plan.fsx"

open System
open System.Formats.Tar
open System.IO
open System.IO.Compression
open System.Security.Cryptography
open System.Text.Json
open System.Text.Json.Nodes
open Contract
open Plan

let revision = Environment.GetEnvironmentVariable "SOURCE_REVISION"
let plan = read ()
let source = "/source/repository/services/project-delivery/controller"
let output = "/output"
let layout = Path.Combine(output, "layout")
let baseImage = "/toolchain/image-base"
let go = "/toolchain/usr/lib/go/bin/go"

require (validRevision revision && plan.SourceRevision = revision) "source revision mismatch"
require (File.Exists go && File.Exists "/toolchain/.ready") "toolchain unavailable"
require (Directory.Exists source) "controller source unavailable"
require (File.Exists(Path.Combine(baseImage, "index.json"))) "base image unavailable"

let executableMode =
    UnixFileMode.UserRead
    ||| UnixFileMode.UserWrite
    ||| UnixFileMode.UserExecute
    ||| UnixFileMode.GroupRead
    ||| UnixFileMode.GroupExecute
    ||| UnixFileMode.OtherRead
    ||| UnixFileMode.OtherExecute

let environment (architecture: string) =
    [ "CGO_ENABLED", "0"
      "GOCACHE", "/build-cache"
      "GOENV", "off"
      "GOOS", "linux"
      "GOARCH", architecture
      "GOMODCACHE", "/toolchain/modules"
      "GOPATH", "/toolchain/gopath"
      "GOPROXY", "off"
      "GOROOT", "/toolchain/usr/lib/go"
      "HOME", "/tmp" ]

let build (architecture: string) =
    let binary =
        Path.Combine(output, "bin", architecture, "project-delivery-controller")

    directory (Path.GetDirectoryName binary) |> ignore

    requireSuccess
        go
        [ "build"
          "-mod=readonly"
          "-trimpath"
          "-ldflags=-s -w -buildid="
          "-o"
          binary
          "." ]
        (Some source)
        (environment architecture)
    |> ignore

    File.SetUnixFileMode(binary, executableMode)
    let header = File.ReadAllBytes binary |> Array.truncate 20
    let machine = if architecture = "amd64" then 62us else 183us

    require
        (header.Length = 20
         && header[0..3] = [| 0x7fuy; 0x45uy; 0x4cuy; 0x46uy |]
         && header[4..5] = [| 2uy; 1uy |]
         && BitConverter.ToUInt16(header, 18) = machine)
        $"invalid {architecture} executable"

    binary

let copyTree (sourceRoot: string) (targetRoot: string) =
    if Directory.Exists targetRoot then
        Directory.Delete(targetRoot, true)

    directory targetRoot |> ignore

    Directory.EnumerateDirectories(sourceRoot, "*", SearchOption.AllDirectories)
    |> Seq.iter (fun path ->
        directory (Path.Combine(targetRoot, Path.GetRelativePath(sourceRoot, path)))
        |> ignore)

    Directory.EnumerateFiles(sourceRoot, "*", SearchOption.AllDirectories)
    |> Seq.iter (fun path -> File.Copy(path, Path.Combine(targetRoot, Path.GetRelativePath(sourceRoot, path))))

let node (path: string) =
    let value = JsonNode.Parse(File.ReadAllText path)
    require (not <| isNull value) $"invalid JSON: {path}"
    value

let text (value: JsonNode) = value.GetValue<string>()

let digestPath (root: string) (digest: string) =
    require (validDigest digest) $"invalid OCI digest: {digest}"
    Path.Combine(root, digest[7..])

let blob (bytes: byte array) =
    let digest = SHA256.HashData bytes |> Convert.ToHexString |> _.ToLowerInvariant()
    File.WriteAllBytes(Path.Combine(layout, "blobs/sha256", digest), bytes)
    $"sha256:{digest}", int64 bytes.Length

let createLayer (architecture: string) (binary: string) =
    let tarPath = Path.Combine(output, $"{architecture}.tar")
    let gzipPath = tarPath + ".gz"

    use tarOutput = File.Create tarPath
    use writer = new TarWriter(tarOutput, TarEntryFormat.Pax, true)
    let entry = PaxTarEntry(TarEntryType.RegularFile, "project-delivery-controller")
    entry.Gid <- 0
    entry.Uid <- 0
    entry.Mode <- executableMode
    entry.ModificationTime <- DateTimeOffset.UnixEpoch
    entry.DataStream <- File.OpenRead binary
    writer.WriteEntry entry
    entry.DataStream.Dispose()
    writer.Dispose()
    tarOutput.Dispose()
    let diff = sha256 tarPath

    use input = File.OpenRead tarPath
    use compressed = File.Create gzipPath
    use encoder = new GZipStream(compressed, CompressionLevel.SmallestSize, true)
    input.CopyTo encoder
    encoder.Dispose()
    compressed.Dispose()
    let digest = sha256 gzipPath
    File.Delete tarPath
    diff, digest, FileInfo(gzipPath).Length, gzipPath

let addLayer (architecture: string) (binary: string) =
    let index = node (Path.Combine(layout, "index.json"))

    let descriptor =
        index["manifests"].AsArray()
        |> Seq.find (fun item -> text (item["platform"]["architecture"]) = architecture)

    let blobs = Path.Combine(layout, "blobs/sha256")
    let manifestPath = digestPath blobs (text (descriptor["digest"]))
    let manifest = node manifestPath
    let configDescriptor = manifest["config"]
    let config = node (digestPath blobs (text (configDescriptor["digest"])))
    let diff, digest, size, layerPath = createLayer architecture binary
    File.Move(layerPath, Path.Combine(blobs, digest), true)
    let layer = JsonObject()
    layer["mediaType"] <- "application/vnd.oci.image.layer.v1.tar+gzip"
    layer["digest"] <- $"sha256:{digest}"
    layer["size"] <- size
    manifest["layers"].AsArray().Add(layer)
    let diffId = $"sha256:{diff}"
    let rootfs = config["rootfs"]
    let diffIds = rootfs["diff_ids"].AsArray()
    diffIds.Add(diffId)

    let configDigest, configSize =
        JsonSerializer.SerializeToUtf8Bytes(config, json) |> blob

    configDescriptor["digest"] <- configDigest
    configDescriptor["size"] <- configSize

    let manifestDigest, manifestSize =
        JsonSerializer.SerializeToUtf8Bytes(manifest, json) |> blob

    descriptor["digest"] <- manifestDigest
    descriptor["size"] <- manifestSize
    File.WriteAllBytes(Path.Combine(layout, "index.json"), JsonSerializer.SerializeToUtf8Bytes(index, json))

let nameIndex () =
    let indexPath = Path.Combine(layout, "index.json")
    let index = node indexPath
    let nested = JsonObject()
    nested["schemaVersion"] <- 2
    nested["mediaType"] <- "application/vnd.oci.image.index.v1+json"
    nested["manifests"] <- index["manifests"].DeepClone()
    let digest, size = JsonSerializer.SerializeToUtf8Bytes(nested, json) |> blob
    let descriptor = JsonObject()
    descriptor["mediaType"] <- "application/vnd.oci.image.index.v1+json"
    descriptor["digest"] <- digest
    descriptor["size"] <- size
    let annotations = JsonObject()
    annotations["org.opencontainers.image.ref.name"] <- "delivery"
    descriptor["annotations"] <- annotations
    index["manifests"] <- JsonArray(descriptor)
    File.WriteAllBytes(indexPath, JsonSerializer.SerializeToUtf8Bytes(index, json))
    File.WriteAllText(Path.Combine(output, "image-digest"), digest + "\n")
    digest

copyTree baseImage layout

[ "amd64"; "arm64" ]
|> List.iter (fun architecture -> build architecture |> addLayer architecture)

printfn "build=image digest=%s" (nameIndex ())