| 1 | build_backend = ({changes,view_changes,semantic,get_key,view_key,fromJS}) ->
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| 2 |
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| 3 | The backend return a function that can be provided to `backend_join`.
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| 4 |
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| 5 | (sources) ->
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| 6 |
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| 7 | For `update` events it will update the document.
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| 8 |
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| 9 | route = sources
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| 10 | .filter operation UPDATE
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| 11 | .thru changes_semantic
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| 12 |
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| 13 | route.create.forEach semantic.create
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| 14 | route.update.forEach semantic.update
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| 15 | route.delete.forEach semantic.delete
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| 16 |
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| 17 | For `subscribe` events it will GET the document and then notify on that current value
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| 18 | and on any future changes. (This is equivalent to a `@most/hold` on the entire database
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| 19 | viewed as a stream, basically, but uses little ressources.)
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| 20 |
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| 21 | subscriptions_keys =
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| 22 | sources
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| 23 | .filter operation SUBSCRIBE
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| 24 | .map Key
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| 25 | .multicast()
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| 26 |
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| 27 | No action is needed for `unsubscribe` events.
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| 28 |
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| 29 | Fetch current value, return a message similar to a row from `_all_docs`.
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| 30 |
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| 31 | values =
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| 32 | subscriptions_keys
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| 33 | .filter is_string # Can only retrieve string keys from a database
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| 34 | .map get_key
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| 35 | .chain most.fromPromise
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| 36 | .filter not_null
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| 37 |
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| 38 | Compute values for wandering-country-view/all by querying the server-side view.
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| 39 |
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| 40 | view_values =
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| 41 | subscriptions_keys
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| 42 | .chain view_key
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| 43 |
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| 44 |
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| 45 | The output is the combination of:
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| 46 |
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| 47 | most.mergeArray [
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| 48 |
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| 49 | - subscriptions to document changes in the database
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| 50 |
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| 51 | changes.map (msg) ->
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| 52 | Immutable.fromJS msg
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| 53 | .merge
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| 54 | op: NOTIFY
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| 55 | value: rev: msg.doc._rev # or msg.changes[0].rev
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| 56 | doc: fromJS msg.doc
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| 57 | key: msg.id
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| 58 |
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| 59 | - requested documents in the database
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| 60 |
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| 61 | values.map (doc) ->
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| 62 | Immutable.Map
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| 63 | op: NOTIFY
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| 64 | id: doc._id
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| 65 | key: doc._id
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| 66 | value: rev: doc._rev
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| 67 | doc: fromJS doc
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| 68 |
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| 69 | - subscriptions to changes in the view
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| 70 |
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| 71 | view_changes.map (msg) ->
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| 72 | Immutable.fromJS msg
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| 73 | .set 'op', NOTIFY
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| 74 |
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| 75 | - requested entries in the view
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| 76 |
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| 77 | view_values.map (msg) ->
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| 78 | Immutable.fromJS msg
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| 79 | .set 'op', NOTIFY
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| 80 |
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| 81 | ]
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| 82 |
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| 83 | module.exports = build_backend
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| 84 | changes_semantic = require 'red-rings-semantic'
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| 85 | {operation,Key,is_string,is_object,not_null,has_key} = require 'abrasive-ducks-transducers'
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| 86 | Immutable = require 'immutable'
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| 87 | most = require 'most'
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| 88 | {UPDATE,SUBSCRIBE,UNSUBSCRIBE,NOTIFY} = require 'red-rings/operations'
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