"General IE based message handling"

Object subclass: IEBase [
    <comment: 'I am a base for IE types'>

    type [
        "Go through the elementId of the class"
        ^ self class elementId
    ]

    writeOnDirect: aMsg [
        "This should be implemented by the subclass"
        self subclassResponsibility
    ]

    writeOn: aMsg [
        aMsg putByte: self class elementId.
        self writeOnDirect: aMsg.
    ]
]

Object subclass: IEMessage [
    <category: 'osmo-messages'>
    | ies type |

    IEMessage class >> initWith: type [
        <category: 'creation'>
        ^ (self new)
            type: type;
            yourself
    ]

    IEMessage class >> findIE: type with: data from: aIEBase [
        "TODO: This needs to move some basic dispatch class"
        "Find the IE that handles the type specified"

        aIEBase allSubclassesDo: [:each |
            each elementId = type
                    ifTrue: [
                       ^ each parseFrom: data.
                ].
            ].

        ^ Exception signal: 'Unsupported IE type: ', type asString.
    ]

    IEMessage class >> decode: aByteArray with: aIEBase [
        | msg dat |
        msg := IEMessage initWith: (aByteArray at: 1).

        dat := aByteArray copyFrom: 2.
        [dat isEmpty not] whileTrue: [
            | type size data |
            type := dat at: 1.
            size := dat at: 2.
            data := dat copyFrom: 1 to: 2 + size.
            dat  := dat copyFrom: 3 + size.

            msg addIe: (self findIE: type with: data from: aIEBase).
        ].

        ^ msg
    ]

    type: aType [
        <category: 'creation'>
        type := aType.
    ]

    type [
        ^ type
    ]

    addIe: aIe [
        <category: 'creation'>
        self ies add: aIe.
    ]

    ies [
        <category: 'access'>
        ies isNil ifTrue: [
            ies := OrderedCollection new.
        ].

        ^ ies
    ]

    findIE: type ifAbsent: block [
        "Find the IE with the type"
        self ies do: [:each |
            each type = type
                ifTrue: [
                    ^ each
            ].
        ].

        ^ block value.
    ]

    findIE: type ifPresent: block [
        "Find the IE with the type"
        self ies do: [:each |
            each type = type
                ifTrue: [
                    ^ block value: each
            ].
        ].

        ^ nil.
    ]

    writeOn: aMsg [
        <category: 'creation'>
        aMsg putByte: type.

        self ies do: [:each | each writeOn: aMsg ]
    ]
]

Object subclass: BCD [
    <category: 'osmo-message'>
    <comment: 'Class to deal with Binary Coded Decimals'>
    BCD class >> encode: aNumber [
        <category: 'access'>
        | col num |
        col := OrderedCollection new.

        num := aNumber.
        1 to: 3 do: [:each |
            col add: num \\ 10.
            num := num // 10.
        ].

        ^ col reverse asByteArray
    ]

    BCD class >> decode: aByteArray [
        <category: 'access'>
        | num cum |

        num := 0.
        cum := 1.
        aByteArray size to: 1 by: -1 do: [:each |
            | at |
            num := num + ((aByteArray at: each) * cum).
            cum := cum * 10.
        ].

        ^ num
    ]
]