Work-in-progress Azure Table Storage

AzureTable.pq

section AzStorage;

[DataSource.Kind="TableStorage"]
shared TableStorage.Contents = (url) =>
        Text.FromBinary(Web.Contents(url, [Headers=SignRequest(url)]));

[DataSource.Kind="TableStorage"]
shared FileStorage.Contents = (url) =>
        Text.FromBinary(Web.Contents(url, [Headers=SignRequestBlob(url)]));

[DataSource.Kind="TableStorage"]
shared TableStorage.Action = (verb, url, body) =>
        WebAction.Request(verb, url, [Headers=SignRequest(url) & [#"Content-Type"="application/json"], Content=Json.FromValue(body)]);

[DataSource.Kind="TableStorage"]
shared TableStorage.Table = (url, table) => Table.View(null, []
);
// Text.FromBinary(Web.Contents(url, [Headers=SignRequest(url)]));

TableStorage = [
    Authentication = [Key=null],
    Label = "TableStorage",
    Type = "Custom",
    MakeResourcePath = MakeResourcePath,
    ParseResourcePath = (resourcePath) => { resourcePath },
    TestConnection = (resource) => { "TableStorage.Contents", resource }
];

DataSourceError = "DataSource.Error";
ExpressionError = "Expression.Error";

MakeResourcePath = (url as text) as text =>
    let
        parts = Uri.Parts(url),
        portText = if parts[Port]? = null or
            (parts[Port]? = 80 and Text.Lower(parts[Scheme]) = "http") or
            (parts[Port]? = 443 and Text.Lower(parts[Scheme]) = "https")
                then ""
                else ":" & Number.ToText(parts[Port]),
        resourcePath = Text.Lower(parts[Scheme] & "://" & parts[Host] & portText)
    in
        resourcePath;

SignRequest = (url) =>
    let
        parts = Uri.Parts(url),
        account = Text.Split(parts[Host], "."){0},
        resource = "/" & account & Text.Split(parts[Path], "?"){0},
        date = DateTimeZone.ToText(DateTimeZone.UtcNow(), "r"),
        stringToSign = date & "#(lf)" & resource,
        payload = Text.ToBinary(stringToSign, TextEncoding.Utf8),
        password = Extension.CurrentCredential()[Password]?,
        key = if password = null then "" else password,
        secret = try Binary.FromText(key, BinaryEncoding.Base64) otherwise #binary({0}),
        signature = Binary.ToText(Crypto.CreateHmac(CryptoAlgorithm.SHA256, secret, payload), BinaryEncoding.Base64)
    in
        [
            Authorization = "SharedKeyLite " & account & ":" & signature,
            Accept = "application/json;odata=nometadata",
            #"x-ms-version" = "2018-03-28",
            #"x-ms-date" = DateTimeZone.ToText(DateTimeZone.UtcNow(), "r")
        ];

SignRequestBlob = (url) =>
    let
        parts = Uri.Parts(url),
        account = Text.Split(parts[Host], "."){0},
        resource = "/" & account & Text.Split(parts[Path], "?"){0},
        date = DateTimeZone.ToText(DateTimeZone.UtcNow(), "r"),
        stringToSign = "GET#(lf)#(lf)#(lf)#(lf)x-ms-date:" & date & "#(lf)x-ms-version:2018-03-28#(lf)" & resource,
        payload = Text.ToBinary(stringToSign, TextEncoding.Utf8),
        password = Extension.CurrentCredential()[Password]?,
        key = if password = null then "" else password,
        secret = try Binary.FromText(key, BinaryEncoding.Base64) otherwise #binary({0}),
        signature = Binary.ToText(Crypto.CreateHmac(CryptoAlgorithm.SHA256, secret, payload), BinaryEncoding.Base64)
    in
        [
            Authorization = "SharedKeyLite " & account & ":" & signature,
            Accept = "application/json;odata=nometadata",
            #"x-ms-version" = "2018-03-28",
            #"x-ms-date" = DateTimeZone.ToText(DateTimeZone.UtcNow(), "r")
        ];