#load "model.fsx"

open System
open System.IO
open System.Security.Cryptography
open System.Text

let check condition message =
    if not condition then
        failwith message

let root =
    Path.Combine(__SOURCE_DIRECTORY__, ".tests", Guid.NewGuid().ToString("N"))

let destination = Path.Combine(root, "model_cache", "model.onnx")
let bytes = Encoding.UTF8.GetBytes "synthetic model"
let expected = SHA256.HashData bytes |> Convert.ToHexString |> _.ToLowerInvariant()
let mutable downloads = 0

let download (output: Stream) =
    downloads <- downloads + 1
    output.Write bytes

let verify () =
    check (File.ReadAllBytes destination = bytes) "installed bytes differ"
    check (not (File.Exists(destination + ".incoming"))) "partial file remains"

try
    check (Model.install expected destination download = Model.Installed) "empty cache was not installed"
    verify ()
    check (downloads = 1) "empty cache download count differs"

    let offline (_: Stream) =
        failwith "cached model attempted a download"

    check (Model.install expected destination offline = Model.Cached) "valid cache was not reused"
    verify ()

    File.WriteAllText(destination, "corrupt model")
    check (Model.install expected destination download = Model.Installed) "corrupt cache was not replaced"
    verify ()
    check (downloads = 2) "corrupt cache download count differs"

    let stale = Encoding.UTF8.GetBytes "retained model"
    File.WriteAllBytes(destination, stale)

    let mismatch (output: Stream) =
        output.Write(Encoding.UTF8.GetBytes "wrong model")

    let mutable rejected = false

    try
        Model.install expected destination mismatch |> ignore
    with :? InvalidOperationException ->
        rejected <- true

    check rejected "checksum mismatch was accepted"
    check (File.ReadAllBytes destination = stale) "checksum mismatch replaced the retained model"
    check (not (File.Exists(destination + ".incoming"))) "checksum mismatch left a partial file"

    let interrupted (output: Stream) =
        output.Write(bytes.AsSpan(0, 4))
        raise (IOException "synthetic interrupted download")

    rejected <- false

    try
        Model.install expected destination interrupted |> ignore
    with :? IOException ->
        rejected <- true

    check rejected "download error was suppressed"
    check (File.ReadAllBytes destination = stale) "download error replaced the retained model"
    check (not (File.Exists(destination + ".incoming"))) "download error left a partial file"
    printfn "PASS: empty cache, cached/offline model, corrupt cache, checksum mismatch and interrupted download"
finally
    Directory.Delete(root, true)