/*
 File: JAHPCacheStoragePolicy.m
 Abstract: A function to determine the cache storage policy for a request.
 Version: 1.1
 
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 */

#import "JAHPCacheStoragePolicy.h"

extern NSURLCacheStoragePolicy JAHPCacheStoragePolicyForRequestAndResponse(NSURLRequest * request, NSHTTPURLResponse * response)
// See comment in header.
{
    BOOL                        cacheable;
    NSURLCacheStoragePolicy     result;
    
    assert(request != NULL);
    assert(response != NULL);
    
    // First determine if the request is cacheable based on its status code.
    
    switch ([response statusCode]) {
        case 200:
        case 203:
        case 206:
        case 301:
        case 304:
        case 404:
        case 410: {
            cacheable = YES;
        } break;
        default: {
            cacheable = NO;
        } break;
    }
    
    // If the response might be cacheable, look at the "Cache-Control" header in
    // the response.
    
    // IMPORTANT: We can't rely on -rangeOfString: returning valid results if the target
    // string is nil, so we have to explicitly test for nil in the following two cases.
    
    if (cacheable) {
        NSString *  responseHeader;
        
        responseHeader = [[response allHeaderFields][@"Cache-Control"] lowercaseString];
        if ( (responseHeader != nil) && [responseHeader rangeOfString:@"no-store"].location != NSNotFound) {
            cacheable = NO;
        }
    }
    
    // If we still think it might be cacheable, look at the "Cache-Control" header in
    // the request.
    
    if (cacheable) {
        NSString *  requestHeader;
        
        requestHeader = [[request allHTTPHeaderFields][@"Cache-Control"] lowercaseString];
        if ( (requestHeader != nil)
            && ([requestHeader rangeOfString:@"no-store"].location != NSNotFound)
            && ([requestHeader rangeOfString:@"no-cache"].location != NSNotFound) ) {
            cacheable = NO;
        }
    }
    
    // Use the cacheable flag to determine the result.
    
    if (cacheable) {
        
        // This code only caches HTTPS data in memory.  This is inline with earlier versions of
        // iOS.  Modern versions of iOS use file protection to protect the cache, and thus are
        // happy to cache HTTPS on disk.  I've not made the correspondencing change because
        // it's nice to see all three cache policies in action.
        
        if ([[[[request URL] scheme] lowercaseString] isEqual:@"https"]) {
            result = NSURLCacheStorageAllowedInMemoryOnly;
        } else {
            result = NSURLCacheStorageAllowed;
        }
    } else {
        result = NSURLCacheStorageNotAllowed;
    }
    
    return result;
}
