From d041897a0813d8de4bde18b242355a5514e324bf Mon Sep 17 00:00:00 2001
From: zjhmale <zjhmale@gmail.com>
Date: Sun, 21 May 2017 22:49:42 +0800
Subject: [PATCH] Fixes #112

---
 src/analysis/common.js                   |  7 ++--
 src/controller.js                        | 17 ++++++----
 src/idris/commands.js                    | 16 +++++----
 src/maybe.js                             | 42 ++++++++++++++++++++++++
 src/providers/ipkg/completionProvider.js |  7 ++--
 5 files changed, 72 insertions(+), 17 deletions(-)
 create mode 100644 src/maybe.js

diff --git a/src/analysis/common.js b/src/analysis/common.js
index 681e56f..7d654f6 100644
--- a/src/analysis/common.js
+++ b/src/analysis/common.js
@@ -2,6 +2,7 @@ const fs = require("fs")
 const glob = require("glob")
 const _ = require('lodash')
 const vscode = require('vscode')
+const Maybe = require('../maybe.js')
 
 const idrisKeywords = [
   "if",
@@ -206,8 +207,10 @@ let getAllFiles = (ext) => {
       return file.endsWith(`.${ext}`)
     })
   } else {
-    let uri = vscode.window.activeTextEditor.document.uri.fsPath
-    return uri.endsWith(ext) ? [uri] : []
+    return Maybe.of(vscode.window.activeTextEditor)
+      .map((editor) => { return editor.document.uri.fsPath })
+      .map((uri) => { return uri.endsWith(ext) ? [uri] : [] })
+      .getOrElse([])
   }
 }
 
diff --git a/src/controller.js b/src/controller.js
index 4e86c4f..cb9adce 100644
--- a/src/controller.js
+++ b/src/controller.js
@@ -5,6 +5,7 @@ const vscode = require('vscode')
 const fs = require('fs')
 const cp = require('child_process')
 const path = require('path')
+const Maybe = require('./maybe')
 
 const IDRIS_MODE = [
   { language: 'idris', scheme: 'file' },
@@ -71,13 +72,15 @@ let reInitialize = () => {
 }
 
 let withCompilerOptions = (callback) => {
-  let document = vscode.window.activeTextEditor.document
-  if (!IDRIS_MODE.map((mode) => { return mode.language }).includes(document.languageId)) return
-  let uri = document.uri.fsPath
-
-  getCompilerOptsPromise().subscribe((compilerOptions) => {
-    commands.initialize(compilerOptions)
-    callback(uri)
+  Maybe.of(vscode.window.activeTextEditor).map((editor) => {
+    let document = editor.document
+    if (!IDRIS_MODE.map((mode) => { return mode.language }).includes(document.languageId)) return
+    let uri = document.uri.fsPath
+  
+    getCompilerOptsPromise().subscribe((compilerOptions) => {
+      commands.initialize(compilerOptions)
+      callback(uri)
+    })
   })
 }
 
diff --git a/src/idris/commands.js b/src/idris/commands.js
index e2c2dd4..f12ff60 100644
--- a/src/idris/commands.js
+++ b/src/idris/commands.js
@@ -6,6 +6,7 @@ const common = require('../analysis/common')
 const findDefinition = require('../analysis/find-definition')
 const Rx = require('rx-lite')
 const path = require('path')
+const Maybe = require('../maybe')
 
 let model = null
 let checkNotTotalModel = null
@@ -102,13 +103,16 @@ let getWord = () => {
  * Get the column of the first character of a concrete line of code
  */
 let getStartColumn = (line) => {
-  if (line >= vscode.window.activeTextEditor.document.lineCount)
-    return 0
+  return Maybe.of(vscode.window.activeTextEditor).map((editor) => {
+    let document = editor.document
 
-  let document = vscode.window.activeTextEditor.document
-  let textAtLine = document.lineAt(line).text
-  let column = textAtLine.indexOf(textAtLine.trim())
-  return column
+    if (line >= document.lineCount)
+      return 0
+
+    let textAtLine = document.lineAt(line).text
+    let column = textAtLine.indexOf(textAtLine.trim())
+    return column
+  }).getOrElse(0)
 }
 
 let clearTotalityDiagnostics = () => {
diff --git a/src/maybe.js b/src/maybe.js
new file mode 100644
index 0000000..22e02f0
--- /dev/null
+++ b/src/maybe.js
@@ -0,0 +1,42 @@
+//http://jrsinclair.com/articles/2016/marvellously-mysterious-javascript-maybe-monad/
+
+var Maybe = module.exports = function (val) {
+  this.__value = val
+}
+
+Maybe.of = function (val) {
+  return new Maybe(val)
+}
+
+Maybe.prototype.isNothing = function () {
+  return (this.__value === null || this.__value === undefined)
+}
+
+Maybe.prototype.map = function (f) {
+  if (this.isNothing()) {
+    return Maybe.of(null)
+  }
+  return Maybe.of(f(this.__value))
+}
+
+Maybe.prototype.foreach = function (f) {
+  if (!this.isNothing()) {
+    f(this.__value)
+  }
+}
+
+Maybe.prototype.orElse = function (d) {
+  if (this.isNothing()) {
+    return Maybe.of(d)
+  }
+
+  return this
+}
+
+Maybe.prototype.getOrElse = function (d) {
+  if (this.isNothing()) {
+    return d
+  }
+
+  return this.__value
+}
diff --git a/src/providers/ipkg/completionProvider.js b/src/providers/ipkg/completionProvider.js
index d50afb7..ecb84e3 100644
--- a/src/providers/ipkg/completionProvider.js
+++ b/src/providers/ipkg/completionProvider.js
@@ -1,12 +1,15 @@
 const common = require('../../analysis/common')
 const completionUtil = require('../completionUtil')
 const vscode = require('vscode')
+const Maybe = require('../../maybe')
 
 let identList
 
 let buildCompletionList = () => {
-  let uri = vscode.window.activeTextEditor.document.uri.fsPath
-  identList = common.getIdents(uri)
+  Maybe.of(vscode.window.activeTextEditor).map((editor) => {
+    let uri = editor.document.uri.fsPath
+    identList = common.getIdents(uri)
+  })
 }
 
 let IPKGCompletionProvider = (function () {