(PureBasic) 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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IncludeFile "CkHttpCurl.pb"
IncludeFile "CkJsonObject.pb"

Procedure ChilkatExample()

    success.i = 0

    ; 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 = 0

    ; --------------------------------------------------------------------------------------------------------
    ; 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.
    jsonAuth.i = CkJsonObject::ckCreate()
    If jsonAuth.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; 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
    CkJsonObject::setCkEnableSecrets(jsonAuth, 1)

    success = CkJsonObject::ckUpdateString(jsonAuth,"oauth2.client_id","!!sharepoint|oauth2|client_id")
    If success = 1
        success = CkJsonObject::ckUpdateString(jsonAuth,"oauth2.client_secret","!!sharepoint|oauth2|client_secret")
    EndIf

    If success = 1
        success = CkJsonObject::ckUpdateString(jsonAuth,"oauth2.token_endpoint","!!sharepoint|oauth2|token_endpoint")
    EndIf

    If success = 0
        Debug CkJsonObject::ckLastErrorText(jsonAuth)
        CkJsonObject::ckDispose(jsonAuth)
        ProcedureReturn
    EndIf

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

    ; ---------------------------------------------------------------------------------------------------

    curl.i = CkHttpCurl::ckCreate()
    If curl.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; 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.
    CkHttpCurl::ckSetAuth(curl,jsonAuth)

    ; Define values that are already known.
    ; 
    ; These variables are referenced in curl commands using
    ; {{variable_name}} substitution syntax.
    CkHttpCurl::ckSetVar(curl,"sharepoint_hostname","example.sharepoint.com")
    CkHttpCurl::ckSetVar(curl,"site_name","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.
    CkHttpCurl::ckAddFunction(curl,"getSite","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.
    CkHttpCurl::ckAddOutput(curl,"getSite","id","site_id")

    ; The download request also requires the drive ID of the Documents
    ; document library.
    ; 
    ; Microsoft Graph refers to document libraries as "drives".
    CkHttpCurl::ckAddFunction(curl,"getDrives","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.
    CkHttpCurl::ckAddOutput2(curl,"getDrives","value","name","Documents",1,"id","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.
    curlCommand.s = "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 = CkHttpCurl::ckDoYourThing(curl,curlCommand)
    If success = 0
        Debug CkHttpCurl::ckLastErrorText(curl)
        CkJsonObject::ckDispose(jsonAuth)
        CkHttpCurl::ckDispose(curl)
        ProcedureReturn
    EndIf

    ; 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.
    statusCode.i = CkHttpCurl::ckStatusCode(curl)
    If statusCode <> 200
        Debug CkHttpCurl::ckResponseBodyStr(curl)
        Debug "status code = " + Str(statusCode)
        CkJsonObject::ckDispose(jsonAuth)
        CkHttpCurl::ckDispose(curl)
        ProcedureReturn
    EndIf

    ; The file has been downloaded successfully and written to:
    ; 
    ;   c:/temp/qa_output/starfish.jpg
    ; 
    Debug "Success."


    CkJsonObject::ckDispose(jsonAuth)
    CkHttpCurl::ckDispose(curl)


    ProcedureReturn
EndProcedure