View Source Chord.Delta (Chord v0.2.0)
Provides utilities for calculating, merging, and formatting context deltas.
This module contains functions to:
- Compute the differences (deltas) between two contexts.
- Merge multiple deltas into a single representation.
- Format deltas for communication or storage purposes.
The formatting of deltas is customizable. Developers can define their own formatter module
implementing the Chord.Delta.Formatter.Behaviour
and configure it in their application.
By default, the library uses Chord.Delta.Formatter.Default
.
Summary
Functions
Calculates the delta between two contexts.
Formats a delta map for external use using the configured delta formatter.
Merges a list of deltas into a single delta.
Functions
Calculates the delta between two contexts.
Given a current_context
and a new_context
, this function determines the differences:
- Keys present in
new_context
but not incurrent_context
are marked as:added
. - Keys present in both but with differing values are marked as
:modified
. - Keys present in
current_context
but absent innew_context
are marked as:removed
.
Parameters
current_context
(map): The original context.new_context
(map): The updated context.
Returns
- (map): A map representing the delta, where each key maps to a change descriptor.
Example
iex> current_context = %{a: 1, b: 2, c: 3}
iex> new_context = %{a: 1, b: 5, d: 4}
iex> Chord.Delta.calculate_delta(current_context, new_context)
%{
b: %{action: :modified, old_value: 2, value: 5},
c: %{action: :removed, old_value: 3},
d: %{action: :added, value: 4}
}
Formats a delta map for external use using the configured delta formatter.
This function delegates the formatting process to the delta formatter configured in your application.
By default, it uses the Chord.Delta.Formatter.Default
module, but you can provide a custom formatter
to handle deltas according to your application's requirements.
The metadata
parameter provides flexibility for passing additional information to the formatter.
While common keys like :context_id
and :version
are supported by the default formatter,
custom formatters can utilize any metadata relevant to their implementation.
Parameters
delta
(map): The delta map representing changes to the context.metadata
(map): A dynamic map containing additional information for the formatter. Common keys include::context_id
- The identifier of the context.:version
- The version of the context being formatted.
Returns
- A formatted map or any structure returned by the configured formatter.
Merges a list of deltas into a single delta.
Combines multiple delta maps to produce a unified view of changes. The merging logic ensures:
- If any delta marks a key as
:removed
, it takes precedence. - If multiple deltas modify the same key, the
old_value
is taken from the first modification, and thevalue
from the last. - Otherwise, the latest change is retained.
Parameters
delta_list
(list of maps): A list of deltas to merge.
Returns
- (map): A single delta representing the merged changes.
Example
iex> delta1 = %{a: %{action: :added, value: 1}, b: %{action: :modified, old_value: 2, value: 3}}
iex> delta2 = %{b: %{action: :removed, old_value: 3}, c: %{action: :added, value: 4}}
iex> Chord.Delta.merge_deltas([delta1, delta2])
%{
a: %{action: :added, value: 1},
b: %{action: :removed, old_value: 3},
c: %{action: :added, value: 4}
}