(Tcl) REST Follow Redirects

Demonstrates how to follow a 302/303 redirect response.

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load ./chilkat.dll

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

set rest [new_CkRest]

set bTls 1
set port 443
set bAutoReconnect 1
set success [CkRest_Connect $rest "chilkatsoft.com" $port $bTls $bAutoReconnect]
if {$success != 1} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkRest $rest
    exit
}

# Send a POST to a URL that will respond with a 302 redirect..
CkRest_AddQueryParam $rest "firstName" "John"
CkRest_AddQueryParam $rest "lastName" "Doe"
set responseText [CkRest_fullRequestFormUrlEncoded $rest "POST" "/echoPost302.asp"]
if {[CkRest_get_LastMethodSuccess $rest] != 1} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkRest $rest
    exit
}

set statusCode [CkRest_get_ResponseStatusCode $rest]

# Examine the response status code
if {$statusCode < 300} then {
    puts "Not a redirect."
    puts "$responseText"
    delete_CkRest $rest
    exit
}

if {$statusCode > 399} then {
    puts "Error response: Status code = $statusCode"
    puts "$responseText"
    delete_CkRest $rest
    exit
}

puts "Redirect status code = $statusCode"

# The response header will contain a Location field with the redirect URL, such as this:
# Location: http://www.chilkatsoft.com/echoPostFinal.asp

# The response status code determines how the client should behave.
# Here are some common possibilities:

# 301: Moved Permanently
# This and all future requests should be directed to the given URI.  (Keep the original HTTP method for the redirect.  In this case, the 
# original request was a POST, so we POST to the redirect URL.)

# 302: Found (aka Object Moved aka Moved Temporarily)
# This is the most popular redirect code, but also an example of industrial practice contradicting the standard. HTTP/1.0 specification (RFC 1945 ) required the client
# to perform a temporary redirect (the original describing phrase was Moved Temporarily), but popular browsers implemented it as a 303 See Other. Therefore, HTTP/1.1
# added status codes 303 and 307 to disambiguate between the two behaviors. However, the majority of Web applications and frameworks still use the 302 status code
# as if it were the 303.

# 303: See Other
# The response to the request can be found under another URI using a GET method. When received in response to a PUT, it should be assumed that the server has
# received the data and the redirect should be issued with a separate GET message.

# 307: Temporary Redirect
# In this occasion, the request should be repeated with another URI, but future requests can still use the original URI. In contrast to 303, the request method
# should not be changed when reissuing the original request. For instance, a POST request must be repeated using another POST request.

puts [CkRest_responseHeader $rest]

# redirectUrl is a CkUrl
set redirectUrl [CkRest_RedirectUrl $rest]
if {[CkRest_get_LastMethodSuccess $rest] == 0} then {
    puts "No Location header found for redirect."
    delete_CkRest $rest
    exit
}

# Prep for the redirect..
CkRest_ClearAllParts $rest

# Disconnect and re-connect.  
# (This can be skipped if both the host and SSL/TLS conditions are the same.)
CkRest_Disconnect $rest 100
set success [CkRest_Connect $rest [CkUrl_host $redirectUrl] [CkUrl_get_Port $redirectUrl] [CkUrl_get_Ssl $redirectUrl] $bAutoReconnect]
if {$success != 1} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkRest $rest
    exit
}

if {expr [$statusCode == 301]  ||  [$statusCode == 307]} then {
    # Redirect using a POST, sending the same params to the new destination
    CkRest_AddQueryParam $rest "firstName" "John"
    CkRest_AddQueryParam $rest "lastName" "Doe"
    set responseText [CkRest_fullRequestFormUrlEncoded $rest "POST" [CkUrl_path $redirectUrl]]
    if {[CkRest_get_LastMethodSuccess $rest] != 1} then {
        puts [CkRest_lastErrorText $rest]
        delete_CkRest $rest
        exit
    }

}

if {expr [$statusCode == 302]  ||  [$statusCode == 303]} then {
    # Redirect using a GET, sending the query params found in the redirect URL.
    set responseText [CkRest_fullRequestFormUrlEncoded $rest "GET" [CkUrl_pathWithQueryParams $redirectUrl]]
    if {[CkRest_get_LastMethodSuccess $rest] != 1} then {
        puts [CkRest_lastErrorText $rest]
        delete_CkRest $rest
        exit
    }

}

# Show the final status code and the response text.
puts "Final status code = [CkRest_get_ResponseStatusCode $rest]"

puts "Final response text (HTML, XML, JSON, or whatever..)"
puts "$responseText"

delete_CkRest $rest