14 files changed, 284 insertions, 36 deletions

diff --git a/.gitignore b/.gitignore
index 6c22375..fd72c00 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,6 @@
 # ignore history used by rustyline
 history.txt
 ./.idea
+
+.envrc
+result
diff --git a/Cargo.lock b/Cargo.lock
index 8b0baa1..de51705 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -158,6 +158,7 @@ dependencies = [
  "radix_fmt",
  "regex",
  "rustyline",
+ "term_size",
 ]
 
 [[package]]
@@ -374,6 +375,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
 
 [[package]]
+name = "term_size"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e4129646ca0ed8f45d09b929036bafad5377103edd06e50bf574b353d2b08d9"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
+[[package]]
 name = "textwrap"
 version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index ae37294..4527862 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -19,3 +19,4 @@ lazy_static = "1.3.0"
 directories = "2.0.1"
 regex       = "1.1.7"
 num         = "0.2"
+term_size   = "0.3"
diff --git a/default.nix b/default.nix
new file mode 100644
index 0000000..a755ba1
--- /dev/null
+++ b/default.nix
@@ -0,0 +1,6 @@
+let
+  pkgs = import <nixpkgs> {};
+  sources = import ./nix/sources.nix;
+  naersk = pkgs.callPackage sources.naersk {};
+in
+  naersk.buildPackage ./.
diff --git a/nix/sources.json b/nix/sources.json
new file mode 100644
index 0000000..17be642
--- /dev/null
+++ b/nix/sources.json
@@ -0,0 +1,38 @@
+{
+    "naersk": {
+        "branch": "master",
+        "description": "Build rust crates in Nix. No configuration, no code generation, no IFD. Sandbox friendly.",
+        "homepage": "",
+        "owner": "nmattia",
+        "repo": "naersk",
+        "rev": "22b96210b2433228d42bce460f3befbdcfde7520",
+        "sha256": "0qa8jnw71qk1i1fgpydx1nv17cnvlydb9jhd6f7gvhglagm19b4v",
+        "type": "tarball",
+        "url": "https://github.com/nmattia/naersk/archive/22b96210b2433228d42bce460f3befbdcfde7520.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "niv": {
+        "branch": "master",
+        "description": "Easy dependency management for Nix projects",
+        "homepage": "https://github.com/nmattia/niv",
+        "owner": "nmattia",
+        "repo": "niv",
+        "rev": "9d35b9e4837ab88517210b1701127612c260eccf",
+        "sha256": "0q50xhnm8g2yfyakrh0nly4swyygxpi0a8cb9gp65wcakcgvzvdh",
+        "type": "tarball",
+        "url": "https://github.com/nmattia/niv/archive/9d35b9e4837ab88517210b1701127612c260eccf.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixos-19.09",
+        "description": "DEPRECATED! This is an obsolete, read-only mirror of the NixOS/nixpkgs repository.",
+        "homepage": "https://github.com/NixOS/nixpkgs",
+        "owner": "NixOS",
+        "repo": "nixpkgs-channels",
+        "rev": "75f4ba05c63be3f147bcc2f7bd4ba1f029cedcb1",
+        "sha256": "157c64220lf825ll4c0cxsdwg7cxqdx4z559fdp7kpz0g6p8fhhr",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/75f4ba05c63be3f147bcc2f7bd4ba1f029cedcb1.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    }
+}
diff --git a/nix/sources.nix b/nix/sources.nix
new file mode 100644
index 0000000..8a725cb
--- /dev/null
+++ b/nix/sources.nix
@@ -0,0 +1,134 @@
+# This file has been generated by Niv.
+
+let
+
+  #
+  # The fetchers. fetch_<type> fetches specs of type <type>.
+  #
+
+  fetch_file = pkgs: spec:
+    if spec.builtin or true then
+      builtins_fetchurl { inherit (spec) url sha256; }
+    else
+      pkgs.fetchurl { inherit (spec) url sha256; };
+
+  fetch_tarball = pkgs: spec:
+    if spec.builtin or true then
+      builtins_fetchTarball { inherit (spec) url sha256; }
+    else
+      pkgs.fetchzip { inherit (spec) url sha256; };
+
+  fetch_git = spec:
+    builtins.fetchGit { url = spec.repo; inherit (spec) rev ref; };
+
+  fetch_builtin-tarball = spec:
+    builtins.trace
+      ''
+        WARNING:
+          The niv type "builtin-tarball" will soon be deprecated. You should
+          instead use `builtin = true`.
+
+          $ niv modify <package> -a type=tarball -a builtin=true
+      ''
+      builtins_fetchTarball { inherit (spec) url sha256; };
+
+  fetch_builtin-url = spec:
+    builtins.trace
+      ''
+        WARNING:
+          The niv type "builtin-url" will soon be deprecated. You should
+          instead use `builtin = true`.
+
+          $ niv modify <package> -a type=file -a builtin=true
+      ''
+      (builtins_fetchurl { inherit (spec) url sha256; });
+
+  #
+  # Various helpers
+  #
+
+  # The set of packages used when specs are fetched using non-builtins.
+  mkPkgs = sources:
+    let
+      sourcesNixpkgs =
+        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) {};
+      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
+      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
+    in
+      if builtins.hasAttr "nixpkgs" sources
+      then sourcesNixpkgs
+      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
+        import <nixpkgs> {}
+      else
+        abort
+          ''
+            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+            add a package called "nixpkgs" to your sources.json.
+          '';
+
+  # The actual fetching function.
+  fetch = pkgs: name: spec:
+
+    if ! builtins.hasAttr "type" spec then
+      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
+    else if spec.type == "file" then fetch_file pkgs spec
+    else if spec.type == "tarball" then fetch_tarball pkgs spec
+    else if spec.type == "git" then fetch_git spec
+    else if spec.type == "builtin-tarball" then fetch_builtin-tarball spec
+    else if spec.type == "builtin-url" then fetch_builtin-url spec
+    else
+      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
+
+  # Ports of functions for older nix versions
+
+  # a Nix version of mapAttrs if the built-in doesn't exist
+  mapAttrs = builtins.mapAttrs or (
+    f: set: with builtins;
+    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
+  );
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball = { url, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchTarball;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchTarball { inherit url; }
+      else
+        fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl = { url, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchurl;
+    in
+      if lessThan nixVersion "1.12" then
+        fetchurl { inherit url; }
+      else
+        fetchurl attrs;
+
+  # Create the final "sources" from the config
+  mkSources = config:
+    mapAttrs (
+      name: spec:
+        if builtins.hasAttr "outPath" spec
+        then abort
+          "The values in sources.json should not have an 'outPath' attribute"
+        else
+          spec // { outPath = fetch config.pkgs name spec; }
+    ) config.sources;
+
+  # The "config" used by the fetchers
+  mkConfig =
+    { sourcesFile ? ./sources.json
+    , sources ? builtins.fromJSON (builtins.readFile sourcesFile)
+    , pkgs ? mkPkgs sources
+    }: rec {
+      # The sources, i.e. the attribute set of spec name to spec
+      inherit sources;
+
+      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
+      inherit pkgs;
+    };
+in
+mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }
diff --git a/shell.nix b/shell.nix
new file mode 100644
index 0000000..c0e1bb0
--- /dev/null
+++ b/shell.nix
@@ -0,0 +1,10 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  buildInputs = with pkgs; [
+    cargo
+    rustc
+    rustfmt
+    pkg-config
+  ];
+}
diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..e05d4e3
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,71 @@
+/* Copyright (C) 2019  Akshay Oppiliappan <[email protected]>
+ * Refer to LICENCE for more information.
+ * */
+
+use std::iter::ExactSizeIterator;
+
+use crate::lex;
+
+#[derive(Debug)]
+pub enum CalcError {
+    Math(Math),
+    Syntax(String),
+    Parser(String),
+    Help,
+}
+
+#[derive(Debug)]
+pub enum Math {
+    DivideByZero,
+    OutOfBounds,
+    UnknownBase,
+}
+
+pub fn handler(e: CalcError) -> String {
+    match e {
+        CalcError::Math(math_err) => match math_err {
+            Math::DivideByZero => "Math Error: Divide by zero error!".to_string(),
+            Math::OutOfBounds => "Domain Error: Out of bounds!".to_string(),
+            Math::UnknownBase => "Base too large! Accepted ranges: 0 - 36".to_string(),
+        },
+        CalcError::Syntax(details) => format!("Syntax Error: {}", details),
+        CalcError::Parser(details) => format!("Parser Error: {}", details),
+        CalcError::Help => {
+            // calculate max width but ideally this should be calculated once
+            let mut max_width = 79; // capped at 79
+            if let Some((w, _)) = term_size::dimensions() {
+                if w < max_width {
+                    max_width = w;
+                }
+            }
+            let operators: Vec<_> = lex::OPERATORS.keys().map(|c| c.to_string()).collect();
+            format!(
+                "Constants\n{}\nFunctions\n{}\nOperators\n{}\n",
+                blocks(max_width, lex::CONSTANTS.keys().cloned()),
+                blocks(max_width, lex::FUNCTIONS.keys().cloned()),
+                operators.join(" ")
+            )
+        }
+    }
+}
+
+/// Convert iterator into strings of chunks of 8 right padded with space.
+fn blocks(
+    max_width: usize,
+    mut iter: impl Iterator<Item = &'static str> + ExactSizeIterator,
+) -> String {
+    // multiply by eight since we are formatting it into chunks of 8
+    let items_per_line = max_width / 8;
+    let full_bytes = (iter.len() - iter.len() % items_per_line) * 8;
+    let part_bytes = iter.len() % items_per_line * 8; // leftovers
+    let n_newlines = iter.len() / items_per_line + if part_bytes > 0 { 1 } else { 0 };
+    let mut s = String::with_capacity(full_bytes + part_bytes + n_newlines);
+    for _ in 0..n_newlines {
+        for item in iter.by_ref().take(items_per_line) {
+            s.extend(format!("{:>8}", item).chars());
+        }
+        s.push('\n');
+    }
+    debug_assert_eq!(s.capacity(), s.len()); // check capacity calculation
+    s
+}
diff --git a/src/error/mod.rs b/src/error/mod.rs
deleted file mode 100644
index ec2b555..0000000
--- a/src/error/mod.rs
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright (C) 2019  Akshay Oppiliappan <[email protected]>
- * Refer to LICENCE for more information.
- * */
-
-#[derive(Debug)]
-pub enum CalcError {
-    Math(Math),
-    Syntax(String),
-    Parser(String),
-}
-
-#[derive(Debug)]
-pub enum Math {
-    DivideByZero,
-    OutOfBounds,
-    UnknownBase,
-}
-
-pub fn handler(e: CalcError) -> String {
-    match e {
-        CalcError::Math(math_err) => match math_err {
-            Math::DivideByZero => "Math Error: Divide by zero error!".to_string(),
-            Math::OutOfBounds => "Domain Error: Out of bounds!".to_string(),
-            Math::UnknownBase => "Base too large! Accepted ranges: 0 - 36".to_string(),
-        },
-        CalcError::Syntax(details) => format!("Syntax Error: {}", details),
-        CalcError::Parser(details) => format!("Parser Error: {}", details),
-    }
-}
diff --git a/src/format/mod.rs b/src/format.rs
index 45673d7..45673d7 100644
--- a/src/format/mod.rs
+++ b/src/format.rs
diff --git a/src/lex/mod.rs b/src/lex.rs
index 3222c12..76f61a0 100644
--- a/src/lex/mod.rs
+++ b/src/lex.rs
@@ -5,9 +5,8 @@
 use lazy_static::lazy_static;
 use std::collections::HashMap;
 
-use crate::CONFIGURATION;
-
 use crate::error::{CalcError, Math};
+use crate::CONFIGURATION;
 
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub struct Operator {
@@ -70,14 +69,14 @@ pub enum Token {
 }
 
 lazy_static! {
-    static ref CONSTANTS: HashMap<&'static str, Token> = {
+    pub static ref CONSTANTS: HashMap<&'static str, Token> = {
         let mut m = HashMap::new();
         m.insert("e",  Token::Num(std::f64::consts::E));
         m.insert("pi", Token::Num(std::f64::consts::PI));
         m
     };
 
-    static ref FUNCTIONS: HashMap<&'static str, Token> = {
+    pub static ref FUNCTIONS: HashMap<&'static str, Token> = {
         let mut m = HashMap::new();
         m.insert("sin",   Function::token_from_fn("sin".into(),   |x| is_radian_mode(x, CONFIGURATION.radian_mode).sin()));
         m.insert("cos",   Function::token_from_fn("cos".into(),   |x| is_radian_mode(x, CONFIGURATION.radian_mode).cos()));
@@ -106,7 +105,7 @@ lazy_static! {
         m
     };
 
-    static ref OPERATORS: HashMap<char, Token> = {
+    pub static ref OPERATORS: HashMap<char, Token> = {
         let mut m = HashMap::new();
         m.insert('+', Operator::token_from_op('+', |x, y| x + y, 2, true));
         m.insert('-', Operator::token_from_op('-', |x, y| x - y, 2, true));
diff --git a/src/main.rs b/src/main.rs
index 5b7fdb4..75c33bb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -193,8 +193,10 @@ fn parse_arguments() -> Configuration {
 }
 
 pub fn eval_math_expression(input: &str, prev_ans: Option<f64>) -> Result<f64, CalcError> {
-    let input = input.trim();
-    let input = input.replace(" ", "");
+    let input = input.trim().replace(" ", "");
+    if input == "help" {
+        return Err(CalcError::Help);
+    }
     if input.is_empty() {
         return Ok(0.);
     }
diff --git a/src/parse/mod.rs b/src/parse.rs
index aa8bd4b..aa8bd4b 100644
--- a/src/parse/mod.rs
+++ b/src/parse.rs
diff --git a/src/readline/mod.rs b/src/readline.rs
index ea195ee..d689f95 100644
--- a/src/readline/mod.rs
+++ b/src/readline.rs
@@ -12,6 +12,7 @@ use directories::ProjectDirs;
 
 use regex::Regex;
 
+use crate::error::CalcError;
 use crate::eval_math_expression;
 
 pub struct RLHelper {
@@ -67,6 +68,7 @@ impl Highlighter for LineHighlighter {
                 }
                 Owned(coloured)
             }
+            Err(CalcError::Help) => Owned(line.replace("help", "\x1b[36mhelp\x1b[0m")),
             Err(_) => Owned(format!("\x1b[31m{}\x1b[0m", line)),
         }
     }