(ns System
  "Elixir System module — system-level information and operations.

   In CljElixir: (System/argv), (System/halt 0), etc.")

(defn argv
  "Returns command line arguments as a list of strings.
   (System/argv) ;=> [\"--flag\" \"value\"]"
  [])

(defn halt
  "Halts the Erlang runtime. `status` is 0 (success) or positive integer.
   (System/halt 0) ;=> exits with code 0
   (System/halt 1) ;=> exits with code 1
   (System/halt \"crash message\") ;=> prints message and exits"
  ([])
  ([status]))

(defn stop
  "Gracefully stops the system. Runs all shutdown hooks.
   (System/stop 0)"
  ([status]))

(defn cmd
  "Runs an external command. Returns {output, exit_status}.
   (System/cmd \"echo\" [\"hello\"]) ;=> {\"hello\\n\" 0}
   (System/cmd \"ls\" [\"-la\"] :cd \"/tmp\") ;=> with options"
  ([command args])
  ([command args opts]))

(defn shell
  "Runs a shell command. Returns {output, exit_status}.
   (System/shell \"echo hello && echo world\") ;=> {\"hello\\nworld\\n\" 0}"
  ([command])
  ([command opts]))

(defn get-env
  "Gets an environment variable. Returns nil if not set.
   (System/get-env \"HOME\") ;=> \"/Users/ajet\"
   (System/get-env \"MISSING\" \"default\") ;=> \"default\"
   (System/get-env) ;=> all env vars as a map"
  ([])
  ([varname])
  ([varname default]))

(defn put-env
  "Sets an environment variable.
   (System/put-env \"MY_VAR\" \"value\") ;=> :ok
   (System/put-env %{\"KEY1\" \"val1\" \"KEY2\" \"val2\"}) ;=> :ok"
  ([varname value])
  ([env-map]))

(defn delete-env
  "Deletes an environment variable.
   (System/delete-env \"MY_VAR\") ;=> :ok"
  [varname])

(defn fetch-env
  "Fetches an env var. Returns {:ok value} or :error.
   (System/fetch-env \"HOME\") ;=> {:ok \"/Users/ajet\"}"
  [varname])

(defn fetch-env!
  "Fetches an env var. Raises if not set.
   (System/fetch-env! \"HOME\") ;=> \"/Users/ajet\""
  [varname])

(defn cwd
  "Returns the current working directory.
   (System/cwd) ;=> \"/Users/ajet/repos/clje\""
  [])

(defn cwd!
  "Returns the current working directory. Raises on error."
  [])

(defn tmp-dir
  "Returns the system temporary directory.
   (System/tmp-dir) ;=> \"/tmp\""
  [])

(defn tmp-dir!
  "Returns the system temporary directory. Raises on error."
  [])

(defn user-home
  "Returns the user's home directory.
   (System/user-home) ;=> \"/Users/ajet\""
  [])

(defn user-home!
  "Returns the user's home directory. Raises on error."
  [])

(defn monotonic-time
  "Returns monotonic time. Useful for measuring elapsed time.
   (System/monotonic-time) ;=> nanoseconds
   (System/monotonic-time :millisecond) ;=> milliseconds"
  ([])
  ([unit]))

(defn system-time
  "Returns system time (wall clock, not monotonic).
   (System/system-time) ;=> nanoseconds
   (System/system-time :second) ;=> seconds since epoch"
  ([])
  ([unit]))

(defn os-time
  "Returns OS time.
   (System/os-time :second) ;=> seconds since epoch"
  ([])
  ([unit]))

(defn unique-integer
  "Returns a unique integer.
   (System/unique-integer) ;=> -576460752303423485
   (System/unique-integer [:positive :monotonic]) ;=> 1"
  ([])
  ([modifiers]))

(defn version
  "Returns the Elixir version string.
   (System/version) ;=> \"1.19.5\""
  [])

(defn otp-release
  "Returns the OTP release number as a string.
   (System/otp-release) ;=> \"28\""
  [])

(defn build-info
  "Returns a map with build info."
  [])

(defn schedulers
  "Returns the number of schedulers.
   (System/schedulers) ;=> 8"
  [])

(defn schedulers-online
  "Returns the number of online schedulers.
   (System/schedulers-online) ;=> 8"
  [])

(defn pid
  "Returns the PID of the OS process running the VM.
   (System/pid) ;=> \"12345\""
  [])

(defn at-exit
  "Registers a function to run at VM exit.
   (System/at-exit (fn [status] (IO/puts \"bye\")))"
  [fun])

(defn stacktrace
  "Returns the last exception stacktrace for the calling process."
  [])

(defn no-halt
  "Configures whether the system halts on script completion."
  ([status]))

(defn trap-signal
  "Traps an OS signal. Returns {:ok fun} or {:already-registered fun}.
   (System/trap-signal :sigterm (fn [] (System/stop 0)))"
  [signal fun])

(defn untrap-signal
  "Removes a previously registered signal trap."
  [signal id])

(defn compiled-endianness
  "Returns the endianness (:big or :little).
   (System/compiled-endianness) ;=> :little"
  [])