# lab42_message
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## Synopsis
Simple Library to manage Errors and Results.
Its Simplicity is inspired by
Dave Thomas' keynote, condensed here https://pragdave.me/blog/2018/06/02/project-structure.html
## API
A container for error messages.
Defining some severities.
Create results depending on error messages.
Convenience functions for adding, filtering and sorting messages.
### Lab42.Message.add_critical/3
Create a message with severity :critical and add in front of other messages
iex(10)> add_critical([], "Just a critical message", {1, 3})
[%Lab42.Message{message: "Just a critical message", severity: :critical, location: {1, 3}}]
### Lab42.Message.add_debug/3
Create a message with severity :debug and add in front of other messages
iex(2)> add_debug([], "Just a debug message", {1, 3})
[%Lab42.Message{message: "Just a debug message", severity: :debug, location: {1, 3}}]
### Lab42.Message.add_error/3
Create a message with severity :error and add in front of other messages
iex(8)> add_error([], "Just a error message", {1, 3})
[%Lab42.Message{message: "Just a error message", severity: :error, location: {1, 3}}]
### Lab42.Message.add_fatal/3
Create a message with severity :fatal and add in front of other messages
iex(12)> add_fatal([], "Just a fatal message", {1, 3})
[%Lab42.Message{message: "Just a fatal message", severity: :fatal, location: {1, 3}}]
### Lab42.Message.add_info/3
Create a message with severity :info and add in front of other messages
iex(4)> add_info([], "Just a info message", {1, 3})
[%Lab42.Message{message: "Just a info message", severity: :info, location: {1, 3}}]
### Lab42.Message.add_warning/3
Create a message with severity :warning and add in front of other messages
iex(6)> add_warning([], "Just a warning message", {1, 3})
[%Lab42.Message{message: "Just a warning message", severity: :warning, location: {1, 3}}]
### Lab42.Message.make_critical/2
Create a message with severity :critical
iex(11)> make_critical("Just a critical message", {1, 3})
%Lab42.Message{message: "Just a critical message", severity: :critical, location: {1, 3}}
### Lab42.Message.make_debug/2
Create a message with severity :debug
iex(3)> make_debug("Just a debug message", {1, 3})
%Lab42.Message{message: "Just a debug message", severity: :debug, location: {1, 3}}
### Lab42.Message.make_error/2
Create a message with severity :error
iex(9)> make_error("Just a error message", {1, 3})
%Lab42.Message{message: "Just a error message", severity: :error, location: {1, 3}}
### Lab42.Message.make_fatal/2
Create a message with severity :fatal
iex(13)> make_fatal("Just a fatal message", {1, 3})
%Lab42.Message{message: "Just a fatal message", severity: :fatal, location: {1, 3}}
### Lab42.Message.make_info/2
Create a message with severity :info
iex(5)> make_info("Just a info message", {1, 3})
%Lab42.Message{message: "Just a info message", severity: :info, location: {1, 3}}
### Lab42.Message.make_warning/2
Create a message with severity :warning
iex(7)> make_warning("Just a warning message", {1, 3})
%Lab42.Message{message: "Just a warning message", severity: :warning, location: {1, 3}}
### Lab42.Message.max_severity/2
Returns the maximum priority of messages
A list of messages can be passed in
iex(15)> messages =
...(15)> []
...(15)> |> add_error("error1", 1)
...(15)> |> add_info("info2", 2)
...(15)> |> add_warning("warning3", 3)
...(15)> max_severity(messages)
:error
However a list of message tuples is also allowed
iex(16)> messages =
...(16)> []
...(16)> |> add_error("error1", 1)
...(16)> |> add_fatal("fatal2", 2)
...(16)> |> add_warning("warning3", 3)
...(16)> |> messages()
...(16)> max_severity(messages)
:fatal
In accordance of the robustness principle the last can even be mixed
iex(17)> messages =
...(17)> []
...(17)> |> add_error("what an error", 42)
...(17)> |> add_info("what an info", 42)
...(17)> max_severity([{:critical, "", nil}|messages])
:critical
And last, but not least it might be convenient to get the severity_value instead of
the symbolic severity
iex(18)> messages =
...(18)> []
...(18)> |> add_error("what an error", 42)
...(18)> |> add_info("what an info", 42)
...(18)> max_severity([{:critical, "", nil}|messages], value: true)
4
### Lab42.Message.messages/2
Extract messages from a list of messages into a library agnositic form as triples.
As all the `add_*` functions create a list in reverse order, this function also
rereverses the message tuples.
iex(19)> messages =
...(19)> []
...(19)> |> add_error("error1", 1)
...(19)> |> add_info("info2", 2)
...(19)> |> add_warning("warning3", 3)
...(19)> messages(messages)
[ {:error, "error1", 1}, {:warning, "warning3", 3} ]
As you can see only messages with severity of warning and up are returned.
One can of course get messages with less severity too:
iex(20)> messages =
...(20)> []
...(20)> |> add_error("error1", 1)
...(20)> |> add_info("info2", 2)
...(20)> |> add_debug("debug3", 3)
...(20)> messages(messages, severity: :info)
[ {:error, "error1", 1}, {:info, "info2", 2} ]
And, eventually, for your convenience, instead of `severity: :debug` a shorter and more expressive `:all` can be passed in
iex(21)> messages =
...(21)> []
...(21)> |> add_error("error1", 1)
...(21)> |> add_info("info2", 2)
...(21)> |> add_debug("debug3", 3)
...(21)> messages(messages, :all)
[ {:error, "error1", 1}, {:info, "info2", 2}, {:debug, "debug3", 3} ]
### Lab42.Message.result/3
Wrap a value and error messages into a result tuple, messages themselves
are converted to message tuples as with `messages`. Also warnings still
deliver an `:ok` reesult.œ
iex(22)> messages = []
...(22)> |> add_debug("hello", 1)
...(22)> |> add_info("hello again", 2)
...(22)> |> add_warning("world", 3)
...(22)> result(messages, "result")
{:ok, "result", [{:warning, "world", 3}]}
However the presence of errors or worse returns an `:error` result.
N.B. that the input can be a mixture of `Lab42.Message` structs and
agnostic tuples.
iex(23)> messages = [{:fatal, "that was not good", 0}]
...(23)> |> add_debug("hello", 1)
...(23)> result(messages, "result")
{:error, "result", [{:fatal, "that was not good", 0}]}
As with `messages` one can control what level of errors shall be included, here
is an example where warnings are surpressed
iex(24)> messages = []
...(24)> |> add_error("hello", 1)
...(24)> |> add_info("hello again", 2)
...(24)> |> add_warning("world", 3)
...(24)> result(messages, 42, severity: :error)
{:error, 42, [{:error, "hello", 1}]}
## Author
Copyright © 2019 Robert Dober, mailto:robert.dober@gmail.com
## License
[Apache-2.0](LICENSE)
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