add additional tests for vi's 'h' and 'l' motions

test/test.sml

@@ -4,21 +4,218 @@ open InputMsg
 
 val emptyVec = Vector.fromList []
 
+fun withIdx (app: AppType.app_type, idx) =
+  let
+    val
+      { startLine
+      , buffer
+      , searchList
+      , searchString
+      , mode
+      , windowWidth
+      , windowHeight
+      , cursorIdx = _
+      } = app
+  in
+    { startLine = startLine
+    , buffer = buffer
+    , searchList = searchList
+    , searchString = searchString
+    , mode = mode
+    , windowWidth = windowWidth
+    , windowHeight = windowHeight
+    , cursorIdx = idx
+    }
+  end
+
 val cursorTests = describe "cursor operations"
-  [ test "'l' moves cursor leftward by one when cursorIdx < length" (fn _ =>
+  [ test "'h' does not move cursor when cursorIdx = 0" (fn _ =>
       let
         (* arrange *)
         val buffer = LineGap.fromString "hello world"
         val app = AppType.init (buffer, 0, 0)
+        val {cursorIdx = oldCursorIdx, ...} = app
 
         (* act *)
-        val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"l")
+        val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"h")
-
-      (* assert *)
       in
-        Expect.isTrue (cursorIdx = 1)
+        (* assert *)
+        Expect.isTrue (oldCursorIdx = 0 andalso cursorIdx = 0)
       end)
 
+  , test "'h' moves cursor left by one in contiguous string when cursorIdx > 0"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer = LineGap.fromString "hello world"
+           val app = AppType.init (buffer, 0, 0)
+           val app = withIdx (app, 1)
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"h")
+         in
+           (* assert *)
+           Expect.isTrue (cursorIdx = 0)
+         end)
+
+  , test "'h' moves cursor left by one in split string when cursorIdx > 0"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer =
+             { idx = 0
+             , line = 0
+             , leftStrings = []
+             , leftLines = []
+             , rightStrings = ["hello", " world"]
+             , rightLines = [emptyVec, emptyVec]
+             }
+           val app = AppType.init (buffer, 0, 0)
+           val app = withIdx (app, 5)
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"h")
+         in
+           (* assert *)
+           Expect.isTrue (cursorIdx = 4)
+         end)
+
+  , test
+      "'h' moves cursor left by two in contiguous string when prev chr is \\n"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer =
+             { idx = 0
+             , line = 0
+             , leftStrings = []
+             , leftLines = []
+             , rightStrings = ["hello\nworld"]
+             , rightLines = [emptyVec]
+             }
+           val app = AppType.init (buffer, 0, 0)
+           val app = withIdx (app, 6)
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"h")
+         in
+           (* assert *)
+           Expect.isTrue (cursorIdx = 4)
+         end)
+
+  , test "'h' moves cursor left by two in split string when prev chr is \\n"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer =
+             { idx = 0
+             , line = 0
+             , leftStrings = []
+             , leftLines = []
+             , rightStrings = ["hello\n", " world"]
+             , rightLines = [emptyVec, emptyVec]
+             }
+           val app = AppType.init (buffer, 0, 0)
+           val app = withIdx (app, 6)
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"h")
+         in
+           (* assert *)
+           Expect.isTrue (cursorIdx = 4)
+         end)
+
+  , test
+      "'l' moves cursor right by one in contiguous string when cursorIdx < length"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer = LineGap.fromString "hello world"
+           val app = AppType.init (buffer, 0, 0)
+           val {cursorIdx = oldCursorIdx, ...} = app
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"l")
+         in
+           (* assert *)
+           Expect.isTrue (oldCursorIdx = 0 andalso cursorIdx = 1)
+         end)
+
+  , test "'l' moves cursor right by one in split string when cursorIdx < length"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer =
+             { idx = 0
+             , line = 0
+             , leftStrings = []
+             , leftLines = []
+             , rightStrings = ["hello ", "world"]
+             , rightLines = [emptyVec, emptyVec]
+             }
+           val app = AppType.init (buffer, 0, 0)
+           val {cursorIdx = oldCursorIdx, ...} = app
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"l")
+         in
+           (* assert *)
+           Expect.isTrue (oldCursorIdx = 0 andalso cursorIdx = 1)
+         end)
+
+  , test "'l' does not move cursor right by one when cursorIdx = length"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer = LineGap.fromString "hello world\n"
+           val app = AppType.init (buffer, 0, 0)
+           val app = withIdx (app, 10)
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"l")
+         in
+           (* assert *)
+           Expect.isTrue (cursorIdx = 10)
+         end)
+
+  , test
+      "'l' moves right by two in contiguous string when char is followed by \\n"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer = LineGap.fromString "hello\nworld\n"
+           val app = AppType.init (buffer, 0, 0)
+           val app = withIdx (app, 4)
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"l")
+         in
+           (* assert *)
+           Expect.isTrue (cursorIdx = 6)
+         end)
+
+  , test "'l' moves right by two in split string when char is followed by \\n"
+      (fn _ =>
+         let
+           (* arrange *)
+           val buffer =
+             { idx = 0
+             , line = 0
+             , leftStrings = []
+             , leftLines = []
+             , rightStrings = ["hello\n", "world"]
+             , rightLines = [emptyVec, emptyVec]
+             }
+           val app = AppType.init (buffer, 0, 0)
+           val app = withIdx (app, 4)
+
+           (* act *)
+           val ({cursorIdx, ...}, _) = AppUpdate.update (app, CHAR_EVENT #"l")
+         in
+           (* assert *)
+           Expect.isTrue (cursorIdx = 6)
+         end)
+
   , test "'w' moves cursor to start of next word in contiguous string" (fn _ =>
       let
         (* arrange *)