Spreadsheet: Setup and prepare for cell types

This commit adds a generic interface for cell types and hooks it up.
There is no way to set these from the UI, and so they're not saved
anywhere yet.
Also implicitly converts numeric values (strictly integers) to numeric
javascript values, as numbery-looking + numbery-looking === string is
not very interesting. :^)

13 files changed, 468 insertions, 11 deletions

diff --git a/Applications/Spreadsheet/CMakeLists.txt b/Applications/Spreadsheet/CMakeLists.txt
index 5ec5efee9a..e3c4a0766d 100644
--- a/Applications/Spreadsheet/CMakeLists.txt
+++ b/Applications/Spreadsheet/CMakeLists.txt
@@ -1,6 +1,10 @@
 set(SOURCES
     Cell.cpp
     CellSyntaxHighlighter.cpp
+    CellType/Identity.cpp
+    CellType/Numeric.cpp
+    CellType/String.cpp
+    CellType/Type.cpp
     HelpWindow.cpp
     JSIntegration.cpp
     Spreadsheet.cpp
diff --git a/Applications/Spreadsheet/Cell.cpp b/Applications/Spreadsheet/Cell.cpp
index d44d02debf..d7beec0bb3 100644
--- a/Applications/Spreadsheet/Cell.cpp
+++ b/Applications/Spreadsheet/Cell.cpp
@@ -60,6 +60,45 @@ void Cell::set_data(JS::Value new_data)
     evaluated_data = move(new_data);
 }
 
+void Cell::set_type(const StringView& name)
+{
+    auto* cell_type = CellType::get_by_name(name);
+    if (cell_type) {
+        m_type = cell_type;
+        return;
+    }
+
+    ASSERT_NOT_REACHED();
+}
+
+void Cell::set_type_metadata(CellTypeMetadata&& metadata)
+{
+    m_type_metadata = move(metadata);
+}
+
+const CellType& Cell::type() const
+{
+    if (m_type)
+        return *m_type;
+
+    if (kind == LiteralString) {
+        if (data.to_int().has_value())
+            return *CellType::get_by_name("Numeric");
+    }
+
+    return *CellType::get_by_name("Identity");
+}
+
+String Cell::typed_display() const
+{
+    return type().display(const_cast<Cell&>(*this), m_type_metadata);
+}
+
+JS::Value Cell::typed_js_data() const
+{
+    return type().js_value(const_cast<Cell&>(*this), m_type_metadata);
+}
+
 void Cell::update_data()
 {
     TemporaryChange cell_change { sheet->current_evaluated_cell(), this };
diff --git a/Applications/Spreadsheet/Cell.h b/Applications/Spreadsheet/Cell.h
index 6fed58f4b9..f7dd3c71dd 100644
--- a/Applications/Spreadsheet/Cell.h
+++ b/Applications/Spreadsheet/Cell.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include "CellType/Type.h"
 #include "Forward.h"
 #include "JSIntegration.h"
 #include <AK/String.h>
@@ -57,6 +58,16 @@ struct Cell : public Weakable<Cell> {
     void set_data(String new_data);
     void set_data(JS::Value new_data);
 
+    void set_type(const StringView& name);
+    void set_type_metadata(CellTypeMetadata&&);
+
+    String typed_display() const;
+    JS::Value typed_js_data() const;
+
+    const CellType& type() const;
+    const CellTypeMetadata& type_metadata() const { return m_type_metadata; }
+    CellTypeMetadata& type_metadata() { return m_type_metadata; }
+
     String source() const;
 
     JS::Value js_data();
@@ -76,6 +87,8 @@ struct Cell : public Weakable<Cell> {
     Kind kind { LiteralString };
     WeakPtr<Sheet> sheet;
     Vector<WeakPtr<Cell>> referencing_cells;
+    const CellType* m_type { nullptr };
+    CellTypeMetadata m_type_metadata;
 
 private:
     void update_data();
diff --git a/Applications/Spreadsheet/CellType/Identity.cpp b/Applications/Spreadsheet/CellType/Identity.cpp
new file mode 100644
index 0000000000..eed7cb190c
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/Identity.cpp
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Identity.h"
+#include "../Cell.h"
+#include "../Spreadsheet.h"
+
+namespace Spreadsheet {
+
+IdentityCell::IdentityCell()
+    : CellType("Identity")
+{
+}
+
+IdentityCell::~IdentityCell()
+{
+}
+
+String IdentityCell::display(Cell& cell, const CellTypeMetadata&) const
+{
+    return cell.js_data().to_string_without_side_effects();
+}
+
+JS::Value IdentityCell::js_value(Cell& cell, const CellTypeMetadata&) const
+{
+    return cell.js_data();
+}
+
+}
diff --git a/Applications/Spreadsheet/CellType/Identity.h b/Applications/Spreadsheet/CellType/Identity.h
new file mode 100644
index 0000000000..09089153ec
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/Identity.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "Type.h"
+
+namespace Spreadsheet {
+
+class IdentityCell : public CellType {
+
+public:
+    IdentityCell();
+    virtual ~IdentityCell() override;
+    virtual String display(Cell&, const CellTypeMetadata&) const override;
+    virtual JS::Value js_value(Cell&, const CellTypeMetadata&) const override;
+};
+
+}
diff --git a/Applications/Spreadsheet/CellType/Numeric.cpp b/Applications/Spreadsheet/CellType/Numeric.cpp
new file mode 100644
index 0000000000..4218e0d1b2
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/Numeric.cpp
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Numeric.h"
+#include "../Cell.h"
+#include "../Spreadsheet.h"
+
+namespace Spreadsheet {
+
+NumericCell::NumericCell()
+    : CellType("Numeric")
+{
+}
+
+NumericCell::~NumericCell()
+{
+}
+
+String NumericCell::display(Cell& cell, const CellTypeMetadata& metadata) const
+{
+    auto value = js_value(cell, metadata);
+    String string;
+    if (metadata.format.is_null())
+        string = value.to_string_without_side_effects();
+    else
+        string = String::format(metadata.format.characters(), value.to_double(cell.sheet->interpreter())); // FIXME: Somehow make this format less dependent on 'double'.
+
+    if (metadata.length >= 0)
+        return string.substring(0, metadata.length);
+
+    return string;
+}
+
+JS::Value NumericCell::js_value(Cell& cell, const CellTypeMetadata&) const
+{
+    return cell.js_data().to_number(cell.sheet->interpreter());
+}
+
+}
diff --git a/Applications/Spreadsheet/CellType/Numeric.h b/Applications/Spreadsheet/CellType/Numeric.h
new file mode 100644
index 0000000000..e0cd4a295a
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/Numeric.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "Type.h"
+
+namespace Spreadsheet {
+
+class NumericCell : public CellType {
+
+public:
+    NumericCell();
+    virtual ~NumericCell() override;
+    virtual String display(Cell&, const CellTypeMetadata&) const override;
+    virtual JS::Value js_value(Cell&, const CellTypeMetadata&) const override;
+};
+
+}
diff --git a/Applications/Spreadsheet/CellType/String.cpp b/Applications/Spreadsheet/CellType/String.cpp
new file mode 100644
index 0000000000..e8b0ed61d2
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/String.cpp
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "String.h"
+#include "../Cell.h"
+#include "../Spreadsheet.h"
+
+namespace Spreadsheet {
+
+StringCell::StringCell()
+    : CellType("String")
+{
+}
+
+StringCell::~StringCell()
+{
+}
+
+String StringCell::display(Cell& cell, const CellTypeMetadata& metadata) const
+{
+    auto string = cell.js_data().to_string_without_side_effects();
+    if (metadata.length >= 0)
+        return string.substring(0, metadata.length);
+
+    return string;
+}
+
+JS::Value StringCell::js_value(Cell& cell, const CellTypeMetadata& metadata) const
+{
+    auto string = display(cell, metadata);
+    return JS::js_string(cell.sheet->interpreter(), string);
+}
+
+}
diff --git a/Applications/Spreadsheet/CellType/String.h b/Applications/Spreadsheet/CellType/String.h
new file mode 100644
index 0000000000..e4ba28eb24
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/String.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "Type.h"
+
+namespace Spreadsheet {
+
+class StringCell : public CellType {
+
+public:
+    StringCell();
+    virtual ~StringCell() override;
+    virtual String display(Cell&, const CellTypeMetadata&) const override;
+    virtual JS::Value js_value(Cell&, const CellTypeMetadata&) const override;
+};
+
+}
diff --git a/Applications/Spreadsheet/CellType/Type.cpp b/Applications/Spreadsheet/CellType/Type.cpp
new file mode 100644
index 0000000000..80933c1a3d
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/Type.cpp
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Type.h"
+#include "Identity.h"
+#include "Numeric.h"
+#include "String.h"
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+
+static HashMap<String, Spreadsheet::CellType*> s_cell_types;
+static Spreadsheet::StringCell s_string_cell;
+static Spreadsheet::NumericCell s_numeric_cell;
+static Spreadsheet::IdentityCell s_identity_cell;
+
+namespace Spreadsheet {
+
+const CellType* CellType::get_by_name(const StringView& name)
+{
+    return s_cell_types.get(name).value_or(nullptr);
+}
+
+CellType::CellType(const StringView& name)
+{
+    ASSERT(!s_cell_types.contains(name));
+    s_cell_types.set(name, this);
+}
+
+}
diff --git a/Applications/Spreadsheet/CellType/Type.h b/Applications/Spreadsheet/CellType/Type.h
new file mode 100644
index 0000000000..7ed9dbe763
--- /dev/null
+++ b/Applications/Spreadsheet/CellType/Type.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "../Forward.h"
+#include <AK/Forward.h>
+#include <AK/String.h>
+#include <LibJS/Forward.h>
+
+namespace Spreadsheet {
+
+struct CellTypeMetadata {
+    int length { -1 };
+    String format;
+};
+
+class CellType {
+public:
+    static const CellType* get_by_name(const StringView&);
+
+    virtual String display(Cell&, const CellTypeMetadata&) const = 0;
+    virtual JS::Value js_value(Cell&, const CellTypeMetadata&) const = 0;
+    virtual ~CellType() { }
+
+protected:
+    CellType(const StringView& name);
+};
+
+}
diff --git a/Applications/Spreadsheet/JSIntegration.cpp b/Applications/Spreadsheet/JSIntegration.cpp
index 830b664f6f..2431b5e409 100644
--- a/Applications/Spreadsheet/JSIntegration.cpp
+++ b/Applications/Spreadsheet/JSIntegration.cpp
@@ -49,7 +49,7 @@ JS::Value SheetGlobalObject::get(const JS::PropertyName& name, JS::Value receive
         if (auto pos = Sheet::parse_cell_name(name.as_string()); pos.has_value()) {
             auto& cell = m_sheet.ensure(pos.value());
             cell.reference_from(m_sheet.current_evaluated_cell());
-            return cell.js_data();
+            return cell.typed_js_data();
         }
     }
 
diff --git a/Applications/Spreadsheet/SpreadsheetModel.cpp b/Applications/Spreadsheet/SpreadsheetModel.cpp
index 2b92619784..c4c5c286a6 100644
--- a/Applications/Spreadsheet/SpreadsheetModel.cpp
+++ b/Applications/Spreadsheet/SpreadsheetModel.cpp
@@ -50,34 +50,33 @@ GUI::Variant SheetModel::data(const GUI::ModelIndex& index, GUI::ModelRole role)
         return {};
 
     if (role == GUI::ModelRole::Display) {
-        const auto* value = m_sheet->at({ m_sheet->column(index.column()), (size_t)index.row() });
-        if (!value)
+        const auto* cell = m_sheet->at({ m_sheet->column(index.column()), (size_t)index.row() });
+        if (!cell)
             return String::empty();
 
-        if (value->kind == Spreadsheet::Cell::Formula) {
-            if (auto object = as_error(value->evaluated_data)) {
+        if (cell->kind == Spreadsheet::Cell::Formula) {
+            if (auto object = as_error(cell->evaluated_data)) {
                 StringBuilder builder;
                 auto error = object->get("message").to_string_without_side_effects();
                 builder.append("Error: ");
                 builder.append(error);
                 return builder.to_string();
             }
-            return value->evaluated_data.is_empty() ? "" : value->evaluated_data.to_string_without_side_effects();
         }
 
-        return value->data;
+        return cell->typed_display();
     }
 
     if (role == GUI::ModelRole::TextAlignment)
         return {};
 
     if (role == GUI::ModelRole::ForegroundColor) {
-        const auto* value = m_sheet->at({ m_sheet->column(index.column()), (size_t)index.row() });
-        if (!value)
+        const auto* cell = m_sheet->at({ m_sheet->column(index.column()), (size_t)index.row() });
+        if (!cell)
             return {};
 
-        if (value->kind == Spreadsheet::Cell::Formula) {
-            if (as_error(value->evaluated_data))
+        if (cell->kind == Spreadsheet::Cell::Formula) {
+            if (as_error(cell->evaluated_data))
                 return Color(Color::Red);
         }