cleanup

3 files changed, 223 insertions, 0 deletions

diff --git a/aoc2023/build/packages/snag/src/snag.app.src b/aoc2023/build/packages/snag/src/snag.app.src
new file mode 100644
index 0000000..175e326
--- /dev/null
+++ b/aoc2023/build/packages/snag/src/snag.app.src
@@ -0,0 +1,8 @@
+{application, snag, [
+    {vsn, "0.2.1"},
+    {applications, [gleam_stdlib,
+                    gleeunit]},
+    {description, "A boilerplate-free ad-hoc error type"},
+    {modules, [snag]},
+    {registered, []}
+]}.
diff --git a/aoc2023/build/packages/snag/src/snag.erl b/aoc2023/build/packages/snag/src/snag.erl
new file mode 100644
index 0000000..a07f242
--- /dev/null
+++ b/aoc2023/build/packages/snag/src/snag.erl
@@ -0,0 +1,74 @@
+-module(snag).
+-compile([no_auto_import, nowarn_unused_vars]).
+
+-export([new/1, error/1, layer/2, context/2, pretty_print/1, line_print/1]).
+-export_type([snag/0]).
+
+-type snag() :: {snag, binary(), list(binary())}.
+
+-spec new(binary()) -> snag().
+new(Issue) ->
+    {snag, Issue, []}.
+
+-spec error(binary()) -> {ok, any()} | {error, snag()}.
+error(Issue) ->
+    {error, new(Issue)}.
+
+-spec layer(snag(), binary()) -> snag().
+layer(Snag, Issue) ->
+    {snag, Issue, [erlang:element(2, Snag) | erlang:element(3, Snag)]}.
+
+-spec context({ok, EXX} | {error, snag()}, binary()) -> {ok, EXX} |
+    {error, snag()}.
+context(Result, Issue) ->
+    case Result of
+        {ok, _} ->
+            Result;
+
+        {error, Snag} ->
+            {error, layer(Snag, Issue)}
+    end.
+
+-spec pretty_print_cause(list(binary())) -> gleam@string_builder:string_builder().
+pretty_print_cause(Cause) ->
+    _pipe = Cause,
+    _pipe@1 = gleam@list:index_map(
+        _pipe,
+        fun(Index, Line) ->
+            gleam@string:concat(
+                [<<"  "/utf8>>,
+                    gleam@int:to_string(Index),
+                    <<": "/utf8>>,
+                    Line,
+                    <<"\n"/utf8>>]
+            )
+        end
+    ),
+    gleam@string_builder:from_strings(_pipe@1).
+
+-spec pretty_print(snag()) -> binary().
+pretty_print(Snag) ->
+    Builder = gleam@string_builder:from_strings(
+        [<<"error: "/utf8>>, erlang:element(2, Snag), <<"\n"/utf8>>]
+    ),
+    gleam@string_builder:to_string(case erlang:element(3, Snag) of
+            [] ->
+                Builder;
+
+            Cause ->
+                _pipe = Builder,
+                _pipe@1 = gleam@string_builder:append(
+                    _pipe,
+                    <<"\ncause:\n"/utf8>>
+                ),
+                gleam@string_builder:append_builder(
+                    _pipe@1,
+                    pretty_print_cause(Cause)
+                )
+        end).
+
+-spec line_print(snag()) -> binary().
+line_print(Snag) ->
+    _pipe = [gleam@string:append(<<"error: "/utf8>>, erlang:element(2, Snag)) |
+        erlang:element(3, Snag)],
+    gleam@string:join(_pipe, <<" <- "/utf8>>).
diff --git a/aoc2023/build/packages/snag/src/snag.gleam b/aoc2023/build/packages/snag/src/snag.gleam
new file mode 100644
index 0000000..8d39537
--- /dev/null
+++ b/aoc2023/build/packages/snag/src/snag.gleam
@@ -0,0 +1,141 @@
+import gleam
+import gleam/string_builder
+import gleam/string
+import gleam/list
+import gleam/int
+
+/// A Snag is a boilerplate-free error type that can be used to track why an
+/// error happened, though does not store as much detail on specific errors as a
+/// custom error type would.
+///
+/// It is useful in code where it must either pass or fail, and when it fails we
+/// want good debugging information to print to the user. i.e. Command line
+/// tools, data processing pipelines, etc.
+///
+/// If it not suited to code where the application needs to make a decision about
+/// what to do in the event of an error, such as whether to give up or to try
+/// again. i.e. Libraries, web application backends, API clients, etc.
+/// In these situations it is recommended to create a custom type for your errors
+/// as it can be pattern matched on and have any additional detail added as
+/// fields.
+pub type Snag {
+  Snag(issue: String, cause: List(String))
+}
+
+/// A concise alias for a `Result` that uses a `Snag` as the error value.
+pub type Result(t) =
+  gleam.Result(t, Snag)
+
+/// Create a new `Snag` with the given issue text.
+///
+/// See also the `error` function for creating a `Snag` wrapped in a `Result`.
+///
+/// # Example
+///
+/// ```gleam
+/// > new("Not enough credit")
+/// > |> line_print
+/// "error: Not enough credit"
+/// ```
+pub fn new(issue: String) -> Snag {
+  Snag(issue: issue, cause: [])
+}
+
+/// Create a new `Snag` wrapped in a `Result` with the given issue text.
+///
+/// # Example
+///
+/// ```gleam
+/// > error("Not enough credit")
+/// Error(new("Not enough credit"))
+/// ```
+pub fn error(issue: String) -> Result(success) {
+  Error(new(issue))
+}
+
+/// Add additional contextual information to a `Snag`.
+///
+/// See also the `context` function for adding contextual information to a `Snag`
+/// wrapped in a `Result`.
+///
+/// # Example
+///
+/// ```gleam
+/// > new("Not enough credit")
+/// > |> layer("Unable to make purchase")
+/// > |> line_print
+/// "error: Unable to make purchase <- Not enough credit"
+/// ```
+pub fn layer(snag: Snag, issue: String) -> Snag {
+  Snag(issue: issue, cause: [snag.issue, ..snag.cause])
+}
+
+/// Add additional contextual information to a `Snag` wrapped in a `Result`.
+///
+/// # Example
+///
+/// ```gleam
+/// > error("Not enough credit")
+/// > |> context("Unable to make purchase")
+/// > |> result.map_error(line_print)
+/// Error("error: Unable to make purchase <- Not enough credit")
+/// ```
+pub fn context(result: Result(success), issue: String) -> Result(success) {
+  case result {
+    Ok(_) -> result
+    Error(snag) -> Error(layer(snag, issue))
+  }
+}
+
+/// Turn a snag into a multi-line string, optimised for readability.
+///
+/// # Example
+///
+/// ```gleam
+/// > new("Not enough credit")
+/// > |> layer("Unable to make purchase")
+/// > |> layer("Character creation failed")
+/// > |> pretty_print
+/// "error: Character creation failed
+///
+/// cause:
+///   0: Unable to make purchase
+///   1: Not enough credit
+/// "
+/// ```
+pub fn pretty_print(snag: Snag) -> String {
+  let builder = string_builder.from_strings(["error: ", snag.issue, "\n"])
+
+  string_builder.to_string(case snag.cause {
+    [] -> builder
+    cause ->
+      builder
+      |> string_builder.append("\ncause:\n")
+      |> string_builder.append_builder(pretty_print_cause(cause))
+  })
+}
+
+fn pretty_print_cause(cause) {
+  cause
+  |> list.index_map(fn(index, line) {
+    string.concat(["  ", int.to_string(index), ": ", line, "\n"])
+  })
+  |> string_builder.from_strings
+}
+
+/// Turn a snag into a single-line string, optimised for compactness. This may be
+/// useful for logging snags.
+///
+/// # Example
+///
+/// ```gleam
+/// > new("Not enough credit")
+/// > |> layer("Unable to make purchase")
+/// > |> layer("Character creation failed")
+/// > |> pretty_print
+/// "error: Character creation failed <- Unable to make purchase <- Not enough credit"
+/// ```
+pub fn line_print(snag: Snag) -> String {
+  [string.append("error: ", snag.issue), ..snag.cause]
+  |> string.join(" <- ")
+}