metamon

-module(metamon@command).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/metamon/command.gleam").
-export([new/4, no_precondition/3, always/3, name_of/1]).
-export_type([command/2]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " Stateful / model-based testing primitives.\n"
    "\n"
    " A `Command(model, real)` represents one transition that can be\n"
    " applied to two parallel worlds:\n"
    "\n"
    "   * **model**: a pure description of the expected state (typically\n"
    "     a record or a `Dict`). The `next_model` step says how the\n"
    "     command updates this expected state.\n"
    "   * **real**: the system under test (a database connection, a\n"
    "     stateful module, an in-memory cache). The `run` step performs\n"
    "     the command on the real world and returns `Ok(Nil)` on\n"
    "     success or `Error(reason)` when an invariant is violated.\n"
    "\n"
    " The `precondition` decides whether the command can fire in the\n"
    " current model state; the runner skips commands whose preconditions\n"
    " are false.\n"
    "\n"
    " See `metamon/stateful` for the runner that drives a list of\n"
    " commands against an initial `(model, real)` pair.\n"
).

-type command(HWL, HWM) :: {command,
        binary(),
        fun((HWL) -> boolean()),
        fun((HWL) -> HWL),
        fun((HWM) -> {ok, nil} | {error, binary()})}.

-file("src/metamon/command.gleam", 32).
?DOC(" Construct a command. `name` is shown in failure reports.\n").
-spec new(
    binary(),
    fun((HWN) -> boolean()),
    fun((HWN) -> HWN),
    fun((HWO) -> {ok, nil} | {error, binary()})
) -> command(HWN, HWO).
new(Name, Pre, Next, Run) ->
    {command, Name, Pre, Next, Run}.

-file("src/metamon/command.gleam", 54).
?DOC(
    " Construct a command with no precondition — the precondition arm is\n"
    " fixed to `fn(_m) { True }`, so the command's gating step is a\n"
    " no-op.\n"
    "\n"
    " \"No precondition\" is **not** the same as \"always runs\": if the\n"
    " command's `run` returns `Error(reason)`, the runner halts the\n"
    " sequence with `Failed`, and any later commands in the list are\n"
    " skipped. Use `command.new` when the command should be gated on the\n"
    " current model state.\n"
    "\n"
    " `command.always` is a synonym for `no_precondition` kept for\n"
    " backward compatibility; new code should prefer this name because\n"
    " it reads correctly at the call site.\n"
).
-spec no_precondition(
    binary(),
    fun((HWT) -> HWT),
    fun((HWU) -> {ok, nil} | {error, binary()})
) -> command(HWT, HWU).
no_precondition(Name, Next, Run) ->
    {command, Name, fun(_) -> true end, Next, Run}.

-file("src/metamon/command.gleam", 67).
?DOC(
    " Synonym for `no_precondition`. The name reads as \"always runs\",\n"
    " which overstates the contract — the command's `run` can still\n"
    " return `Error`, halting the sequence. Prefer `no_precondition` in\n"
    " new code; this constructor is retained as an alias so existing\n"
    " call sites continue to compile.\n"
).
-spec always(
    binary(),
    fun((HWZ) -> HWZ),
    fun((HXA) -> {ok, nil} | {error, binary()})
) -> command(HWZ, HXA).
always(Name, Next, Run) ->
    no_precondition(Name, Next, Run).

-file("src/metamon/command.gleam", 76).
?DOC(" Get the command's user-facing name.\n").
-spec name_of(command(any(), any())) -> binary().
name_of(Cmd) ->
    erlang:element(2, Cmd).