REBOL interface to GnuCash: Working with the GnuCash XML

Now to take the file we created and start messing with it.

I found an option to turn off compressing the data file for GnuCash, so I want to focus on parsing the XML.

There’s a few REBOL scripts that work with XML; I chose xml-parse.r.  Initially I used its builtin block parsing methods to turn the XML into REBOL blocks that I could work with, but I decided that parsing the entire document into blocks first, just so I could try random REBOL series! functions against it would be a huge waste.  So, I ended up writing a gnucash handler to look for specific elements as they’re parsed and save the child nodes of each as key/value pairs.

As a first try I want to supply the source XML and a request/response block!:
>> gnucash/list read %2011.xml [“gnc:transaction” []]

rebol [
  Title: "Process GnuCash data file"
  File: "%parse-gc-xml.r"
  Date:  13 Dec 2012
  Purpose: {
    interface to gnucash data
  }
]

do %xml-parse.r
gnucash: make xml-parse/parser [
    subjects: copy []
    content: copy ""
    row: none
    set-namespace-aware false

    list: func [ gc-xml [string!] subjects [block!] ][
        self/subjects: copy subjects
        parse-xml gc-xml
        return self/subjects
    ]
	
    handler: make xml-parse/xml-parse-handler [

        characters: func [ characters [string! none!] ][
            if all [ 
                found? row 
                found? characters 
            ][
                append content characters
            ]
        ]
        start-element: func [
            ns-uri [string! none!]
            local-name [string! none!] q-name [string!]
            attr-list [block!]
        ][
            clear head content
            if found? rowset: select subjects q-name [ 
                append/only rowset row: copy []
            ]
        ]
        end-element: func [
            ns-uri [string! none!]
            local-name [string! none!] q-name [string! ]
        ][
            if found? row [ 
                either select subjects q-name 
                    [ row: none ][ repend row [q-name copy content] ]
            ]
        ]
    ] ; handler
] ; gnucash

Try it out.
>> do %parse-gc-xml.r
>> trns: gnucash/list read %../2011.xml [“gnc:transaction” []]
== [“gnc:transaction” [[“trn:id” “a1ddec4b4fe26e84745a8cddac018620” “cmdty:space” “ISO4217” “cmdty:id” “USD” “trn:currency” “” “ts:…
>> trns/1
== “gnc:transaction”
>> trns/2
== [[“trn:id” “a1ddec4b4fe26e84745a8cddac018620” “cmdty:space” “ISO4217” “cmdty:id” “USD” “trn:currency” “” “ts:date” “2011-01-03 0…
>> trns/2/1
== [“trn:id” “a1ddec4b4fe26e84745a8cddac018620” “cmdty:space” “ISO4217” “cmdty:id” “USD” “trn:currency” “” “ts:date” “2011-01-03 00…
>>
>> trns/2/2
== [“trn:id” “1849b854cd0ad3fbbddc94f3d661672a” “cmdty:space” “ISO4217” “cmdty:id” “USD” “trn:currency” “” “ts:date” “2011-05-20 00…

So we can think of trns as having “rows” of gnc:transaction attributes.  Precisely, its second entry is the returned rowset.  If I want the date from the second transaction, I can.

>> select trns/2/2 “ts:date”
== “2011-05-20 00:00:00 -0600”

We can collect multiple rowsets with one call by adding additional element/block! pairs in the argument.

>> result: gnucash/list read %../2011.xml [“gnc:commodity” [] “gnc:account” []]
== [“gnc:commodity” [[“cmdty:space” “ISO4217” “cmdty:id” “USD” “cmdty:get_quotes” “” “cmdty:quote_source” “currency” “cmdty:quote_t…
>> acts: find result “gnc:account”
== [“gnc:account” [[“act:name” “Root Account” “act:id” “6197eee7c4c8c51c914cd3aa4114ef44” “act:type” “ROOT”] [“act:name” “Expenses”…
>> acts/1
== “gnc:account”
>> select acts/2/1 “act:name”
== “Root Account”

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REBOL interface to GnuCash: Uncompressing the data

I first saw REBOL in about 1999 and immediately thought it was about the bitchinest thing since function pointers let me implement polymorphism in C (and assembler).  I am going to try once again, now that I have some free time, to learn it.  As part of a much bigger idea, I want to work with GnuCash files.

GnuCash (I am using version 2.4.8) puts all its data in a compressed file.  I used 7-Zip to check it out and that’s what I’ll use to uncompress it, since I couldn’t get the native REBOL scripts I found to work — but that’s OK, because I can call 7-Zip’s command line version from REBOL.

(Check out how to install on your machine on the REBOL site, please.)

And especially, before I start, I have frankly struggled with this language in the past.  I’ve read that REBOL can be harder to learn if you have a lot of traditional programming experience.

The script should let me select the GnuCash compressed data file to be used as 7-zip’s input and show me the uncompressed data.

Ask for GnuCash input file to uncompress

rebol [
    Title: "Process GnuCash data file"
    File: "%rebcash.r"
    Date: 01 Dec 2012
    Purpose: {
        interface to gnucash data
    }
]

if gc-source-file:
    request-file/title/keep/only/filter
    "Select GnuCash File" "OK" "*.gc" [
    call/console reform [ 
        "C:\Program Files\7-Zip\7z.exe" 'e '-tgzip '-so '-y
            rejoin [ {"} to-local-file clean-path gc-source-file {"} ]
    ]
]

The -so option sends output to stdout.

The /console refinement on call lets me see its output in the REBOL interpreter.

The REBOL rejoin function evaluates the terms in the block and returns a concatenated string of results.  Some magic file system functions are used to turn the REBOL file! type that was returned by request-file into a path the host can be happy with.

So for a simple scripting language, that’s great. Here’s what starts dumping to my screen:

Output in console window