(PureBasic) Download a File from a SharePoint Documents Library

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This example shows how to use Chilkat's HttpCurl class to download a file from the root of a SharePoint Documents document library. The example demonstrates how HttpCurl automatically resolves the SharePoint site name to a site ID, finds the drive ID for the Documents library, locates the file by name, and then downloads the file content using Microsoft Graph.

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IncludeFile "CkStringBuilder.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkHttpCurl.pb"

Procedure ChilkatExample()

    success.i = 0

    ; This example downloads a file named "hamlet.json" from the root of the SharePoint
    ; Documents document library.
    ; 
    ; The example demonstrates how HttpCurl can automatically resolve all of the
    ; information needed to locate and download a file:
    ; 
    ;   site_name            -> site_id
    ;   site_id              -> document_library_id
    ;   document_library_id  -> file_id
    ;   file_id              -> file content
    ; 
    ; The application only provides the SharePoint site name and the desired
    ; filename.  HttpCurl automatically executes the required Microsoft Graph
    ; requests to obtain the remaining values.

    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 first step is to obtain the Microsoft Graph site ID.
    ; 
    ; The application only knows the SharePoint site name, so define
    ; a 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 next step is to find 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")

    ; Now list the contents of the Documents document library.
    CkHttpCurl::ckAddFunction(curl,"getFiles","GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives/{{document_library_id}}/root/children")

    ; Search the returned files for an item named "hamlet.json"
    ; and save its Microsoft Graph item ID in the file_id variable.
    CkHttpCurl::ckAddOutput2(curl,"getFiles","value","name","hamlet.json",1,"id","file_id")

    ; This is the target request.
    ; 
    ; GET -L https://graph.microsoft.com/v1.0/drives/{{document_library_id}}/items/{{file_id}}/content
    ; 
    ; The /content endpoint returns the actual contents of the file.
    ; 
    ; The -L option instructs HttpCurl to follow the redirect returned by
    ; Microsoft Graph.  The Graph API typically responds with a redirect
    ; to the actual file download URL.
    curlCommand.s = "GET -L https://graph.microsoft.com/v1.0/drives/{{document_library_id}}/items/{{file_id}}/content"

    ; Execute the request.
    ; 
    ; HttpCurl examines the target request and determines that both
    ; document_library_id and file_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) getFiles     -> file_id
    ;   4) download     -> file content
    ; 
    ; The final response returned by DoYourThing is the downloaded
    ; file content from the target request.
    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 response body contains the contents of the downloaded file.
    sbFileContents.i = CkStringBuilder::ckCreate()
    If sbFileContents.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkHttpCurl::ckGetResponseSb(curl,sbFileContents)

    ; Optionally save the downloaded content to a local file.
    ; 
    ; The third argument controls whether the file is appended.
    ; Passing ckfalse causes the file to be overwritten if it already exists.
    success = CkStringBuilder::ckWriteFile(sbFileContents,"c:/temp/hamlet.json","utf-8",0)
    If success = 0
        Debug CkStringBuilder::ckLastErrorText(sbFileContents)
        CkJsonObject::ckDispose(jsonAuth)
        CkHttpCurl::ckDispose(curl)
        CkStringBuilder::ckDispose(sbFileContents)
        ProcedureReturn
    EndIf

    Debug "Success."


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


    ProcedureReturn
EndProcedure