# 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.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(15)> messages =
...(15)> []
...(15)> |> add_error("error1", 1)
...(15)> |> add_info("info2", 2)
...(15)> |> add_warning("warning3", 3)
...(15)> 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(16)> messages =
...(16)> []
...(16)> |> add_error("error1", 1)
...(16)> |> add_info("info2", 2)
...(16)> |> add_debug("debug3", 3)
...(16)> 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(17)> messages =
...(17)> []
...(17)> |> add_error("error1", 1)
...(17)> |> add_info("info2", 2)
...(17)> |> add_debug("debug3", 3)
...(17)> messages(messages, :all)
[ {:error, "error1", 1}, {:info, "info2", 2}, {:debug, "debug3", 3} ]
### Lab42.Message.result/2
Wrap a value and error messages into a result tuple
iex(18)> result([], 42)
{:ok, 42, []}
Messages of severity warning or less still deliver a `:ok` result
iex(19)> messages = []
...(19)> |> add_debug("hello", 1)
...(19)> |> add_info("hello again", 2)
...(19)> |> add_warning("world", 3)
...(19)> {:ok, "result", ^messages} = result(messages, "result")
...(19)> true
true
## Author
Copyright © 2019 Robert Dober, mailto:robert.dober@gmail.com
## License
[Apache-2.0](LICENSE)
<!-- SPDX-License-Identifier: Apache-2.0 -->
