Exo-train kata

Given a string representation of a train, print an ASCII-art representation of this train.

• H: locomotive <HHHH
• P: passenger car |OOOO|

Cars are attached together by ::

HPP ---> <HHHH::|OOOO|::|OOOO|

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• R: restaurant car |hThT|

HPRP ---> <HHHH::|OOOO|::|hThT|::|OOOO|

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• H: locomotive attached at the end HHHH>

HPRPH ---> <HHHH::|OOOO|::|hThT|::|OOOO|::HHHH>

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• A car can be deatached from the head or the end of the train

HPRPH ---> toASCIIart ---><HHHH::|OOOO|::|hThT|::|OOOO|::HHHH> ---> detachEnd ---> <HHHH::|OOOO|::|hThT|::|OOOO| ---> detachHead ---> |OOOO|::|hThT|::|OOOO|

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• C: cargo car |____| (when empty) |^^^^| (when full)

HCCC ---> <HHHH::|____|::|____|::|____| ---> fill ---> <HHHH::|^^^^|::|____|::|____| ---> fill ---> <HHHH::|^^^^|::|^^^^|::|____| ---> fill ---> <HHHH::|^^^^|::|^^^^|::|^^^^| ---> fill ---> error: cannot fill a full train

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