(Swift) Download a SharePoint File by Path using HttpCurl

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This example shows how to use Chilkat's HttpCurl class to download a file from SharePoint when the file path within the document library is already known. The example uses Microsoft Graph to automatically resolve the SharePoint site name to a site ID, find the drive ID for the Documents document library, and then download the file directly by path using the Graph root:/path:/content syntax.

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func chilkatTest() {
    var success: Bool = false

    // This example downloads a file from a SharePoint Documents document library
    // when the file's path within the library is already known.
    // 
    // The file downloaded in this example is:
    // 
    //   images/sea_creatures/starfish.jpg
    // 
    // Unlike the previous example  that searched for a file by name and obtained
    // its Microsoft Graph item ID, this example uses the Graph path-based API.
    // 
    // The example demonstrates how HttpCurl automatically resolves:
    // 
    //   site_name  -> site_id
    //   site_id    -> document_library_id
    // 
    // and then uses the known file path to download the file directly.

    success = false

    // --------------------------------------------------------------------------------------------------------
    // Before running this example, create an Azure App Registration and grant it
    // the Microsoft Graph permissions required to access SharePoint.
    // 
    // The application will authenticate using OAuth2 Client Credentials.
    // See:
    // How to Create SharePoint App Registration for OAuth 2.0 Client Credentials
    // --------------------------------------------------------------------------------------------------------

    // Build a JSON authentication configuration.
    // HttpCurl will use this information to automatically obtain OAuth2 access tokens.
    let jsonAuth = CkoJsonObject()!

    // Enable secret lookup.
    // 
    // Instead of hard-coding sensitive values such as the client ID,
    // client secret, and token endpoint, secret specification strings
    // are used.  Chilkat automatically retrieves the actual values from
    // Windows Credential Manager (Windows) or Apple Keychain (macOS).
    // 
    // See:
    // Secret Specification Strings
    jsonAuth.enableSecrets = true

    success = jsonAuth.update("oauth2.client_id", value: "!!sharepoint|oauth2|client_id")
    if success == true {
        success = jsonAuth.update("oauth2.client_secret", value: "!!sharepoint|oauth2|client_secret")
    }

    if success == true {
        success = jsonAuth.update("oauth2.token_endpoint", value: "!!sharepoint|oauth2|token_endpoint")
    }

    if success == false {
        print("\(jsonAuth.lastErrorText!)")
        return
    }

    // Request Microsoft Graph permissions that were granted to the application.
    jsonAuth.update("oauth2.scope", value: "https://graph.microsoft.com/.default")

    // ---------------------------------------------------------------------------------------------------

    let curl = CkoHttpCurl()!

    // Associate the OAuth2 configuration with HttpCurl.
    // 
    // When the request is executed, Chilkat automatically obtains an access token
    // if needed and adds the Authorization: Bearer header to the HTTP request.
    curl.setAuth(jsonAuth)

    // Define values that are already known.
    // 
    // These variables are referenced in curl commands using
    // {{variable_name}} substitution syntax.
    curl.setVar("sharepoint_hostname", varValue: "example.sharepoint.com")
    curl.setVar("site_name", varValue: "test")

    // The download request requires a Microsoft Graph site ID.
    // 
    // Because the application only knows the SharePoint site name,
    // define a helper function that can retrieve the site information.
    curl.addFunction("getSite", curl: "GET https://graph.microsoft.com/v1.0/sites/root:/sites/{{site_name}}")

    // Extract the site's ID and store it in the HttpCurl variable named site_id.
    curl.addOutput("getSite", jsonPath: "id", varName: "site_id")

    // The download request also requires the drive ID of the Documents
    // document library.
    // 
    // Microsoft Graph refers to document libraries as "drives".
    curl.addFunction("getDrives", curl: "GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives")

    // Search the returned drives for the one named "Documents"
    // and save its drive ID in the document_library_id variable.
    curl.addOutput2("getDrives", arrayPath: "value", wherePath: "name", whereValue: "Documents", caseSensitive: true, subPath: "id", varName: "document_library_id")

    // This is the target Microsoft Graph request.
    // 
    // GET /sites/{site-id}/drives/{drive-id}/root:/{path-to-file}:/content
    // 
    // The path-based API allows a file to be downloaded directly when its
    // location within the document library is known.
    // 
    // The -L option causes HttpCurl to follow redirects.
    // Microsoft Graph typically returns a redirect to the actual download URL.
    // 
    // The -o option specifies the output filename.
    // The --output-dir option specifies the directory where the downloaded
    // file will be saved.
    var curlCommand: String? = "GET -L --output-dir c:/temp/qa_output -o starfish.jpg https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives/{{document_library_id}}/root:/images/sea_creatures/starfish.jpg:/content"

    // Execute the request.
    // 
    // HttpCurl examines the target request and determines that both
    // site_id and document_library_id are required.
    // 
    // To obtain these values, it automatically builds and executes
    // the following dependency chain:
    // 
    //   1) getSite    -> site_id
    //   2) getDrives  -> document_library_id
    //   3) download   -> file content
    // 
    // The file is streamed directly to the output file specified by
    // the curl command.
    success = curl.doYourThing(curlCommand)
    if success == false {
        print("\(curl.lastErrorText!)")
        return
    }

    // A successful Graph response should return HTTP 200.
    // Any other status code typically indicates an authentication,
    // permission, site lookup, document library lookup, or file lookup error.
    var statusCode: Int = curl.statusCode.intValue
    if statusCode != 200 {
        print("\(curl.responseBodyStr!)")
        print("status code = \(statusCode)")
        return
    }

    // The file has been downloaded successfully and written to:
    // 
    //   c:/temp/qa_output/starfish.jpg
    // 
    print("Success.")

}