Spreadsheet: Make the XSV parser start with a preview parse

Instead of parsing the whole document. That's really wasteful and
super slow.

4 files changed, 36 insertions, 7 deletions

diff --git a/Userland/Applications/Spreadsheet/ImportDialog.cpp b/Userland/Applications/Spreadsheet/ImportDialog.cpp
index 293ae767cb..7e95c4ea95 100644
--- a/Userland/Applications/Spreadsheet/ImportDialog.cpp
+++ b/Userland/Applications/Spreadsheet/ImportDialog.cpp
@@ -147,7 +147,7 @@ auto CSVImportDialogPage::make_reader() -> Optional<Reader::XSV>
     if (should_trim_trailing)
         behaviours = behaviours | Reader::ParserBehaviour::TrimTrailingFieldSpaces;
 
-    return Reader::XSV(m_csv, traits, behaviours);
+    return Reader::XSV(m_csv, move(traits), behaviours);
 };
 
 void CSVImportDialogPage::update_preview()
@@ -195,6 +195,7 @@ Result<NonnullRefPtrVector<Sheet>, String> ImportDialog::make_and_run_for(String
             NonnullRefPtrVector<Sheet> sheets;
 
             if (reader.has_value()) {
+                reader->parse();
                 if (reader.value().has_error())
                     return String::formatted("CSV Import failed: {}", reader.value().error_string());
 
diff --git a/Userland/Applications/Spreadsheet/Readers/Test/TestXSV.cpp b/Userland/Applications/Spreadsheet/Readers/Test/TestXSV.cpp
index 7a25cba567..0569b59dd4 100644
--- a/Userland/Applications/Spreadsheet/Readers/Test/TestXSV.cpp
+++ b/Userland/Applications/Spreadsheet/Readers/Test/TestXSV.cpp
@@ -18,6 +18,7 @@ TEST_CASE(should_parse_valid_data)
                       4, 5, 6
                       """x", y"z, 9)~~~";
         auto csv = Reader::CSV { data, Reader::default_behaviours() | Reader::ParserBehaviour::ReadHeaders | Reader::ParserBehaviour::TrimLeadingFieldSpaces };
+        csv.parse();
         EXPECT(!csv.has_error());
 
         EXPECT_EQ(csv[0]["Foo"], "1");
@@ -31,6 +32,7 @@ TEST_CASE(should_parse_valid_data)
                       4, "5 "       , 6
                       """x", y"z, 9                       )~~~";
         auto csv = Reader::CSV { data, Reader::default_behaviours() | Reader::ParserBehaviour::ReadHeaders | Reader::ParserBehaviour::TrimLeadingFieldSpaces | Reader::ParserBehaviour::TrimTrailingFieldSpaces };
+        csv.parse();
         EXPECT(!csv.has_error());
 
         EXPECT_EQ(csv[0]["Foo"], "1");
@@ -46,6 +48,7 @@ TEST_CASE(should_fail_nicely)
         auto data = R"~~~(Foo, Bar, Baz
                       x, y)~~~";
         auto csv = Reader::CSV { data, Reader::default_behaviours() | Reader::ParserBehaviour::ReadHeaders | Reader::ParserBehaviour::TrimLeadingFieldSpaces };
+        csv.parse();
         EXPECT(csv.has_error());
         EXPECT_EQ(csv.error(), Reader::ReadError::NonConformingColumnCount);
     }
@@ -54,6 +57,7 @@ TEST_CASE(should_fail_nicely)
         auto data = R"~~~(Foo, Bar, Baz
                       x, y, "z)~~~";
         auto csv = Reader::CSV { data, Reader::default_behaviours() | Reader::ParserBehaviour::ReadHeaders | Reader::ParserBehaviour::TrimLeadingFieldSpaces };
+        csv.parse();
         EXPECT(csv.has_error());
         EXPECT_EQ(csv.error(), Reader::ReadError::QuoteFailure);
     }
@@ -66,6 +70,7 @@ TEST_CASE(should_iterate_rows)
                       4, 5, 6
                       """x", y"z, 9)~~~";
     auto csv = Reader::CSV { data, Reader::default_behaviours() | Reader::ParserBehaviour::ReadHeaders | Reader::ParserBehaviour::TrimLeadingFieldSpaces };
+    csv.parse();
     EXPECT(!csv.has_error());
 
     bool ran = false;
@@ -82,6 +87,7 @@ BENCHMARK_CASE(fairly_big_data)
 
     auto data = file_or_error.value()->read_all();
     auto csv = Reader::CSV { data, Reader::default_behaviours() | Reader::ParserBehaviour::ReadHeaders };
+    csv.parse();
 
     EXPECT(!csv.has_error());
     EXPECT_EQ(csv.size(), 100000u);
diff --git a/Userland/Applications/Spreadsheet/Readers/XSV.cpp b/Userland/Applications/Spreadsheet/Readers/XSV.cpp
index bdce748884..9e3b737fd7 100644
--- a/Userland/Applications/Spreadsheet/Readers/XSV.cpp
+++ b/Userland/Applications/Spreadsheet/Readers/XSV.cpp
@@ -11,12 +11,12 @@ namespace Reader {
 
 ParserBehaviour operator&(ParserBehaviour left, ParserBehaviour right)
 {
-    return static_cast<ParserBehaviour>(static_cast<u32>(left) & static_cast<u32>(right));
+    return static_cast<ParserBehaviour>(to_underlying(left) & to_underlying(right));
 }
 
 ParserBehaviour operator|(ParserBehaviour left, ParserBehaviour right)
 {
-    return static_cast<ParserBehaviour>(static_cast<u32>(left) | static_cast<u32>(right));
+    return static_cast<ParserBehaviour>(to_underlying(left) | to_underlying(right));
 }
 
 void XSV::set_error(ReadError error)
@@ -43,8 +43,22 @@ Vector<String> XSV::headers() const
     return headers;
 }
 
+void XSV::parse_preview()
+{
+    reset();
+    if ((m_behaviours & ParserBehaviour::ReadHeaders) != ParserBehaviour::None)
+        read_headers();
+
+    while (!has_error() && !m_lexer.is_eof()) {
+        if (m_rows.size() >= 10)
+            break;
+        m_rows.append(read_row());
+    }
+}
+
 void XSV::parse()
 {
+    reset();
     if ((m_behaviours & ParserBehaviour::ReadHeaders) != ParserBehaviour::None)
         read_headers();
 
diff --git a/Userland/Applications/Spreadsheet/Readers/XSV.h b/Userland/Applications/Spreadsheet/Readers/XSV.h
index b36fb0d0ed..d5d7bcfb07 100644
--- a/Userland/Applications/Spreadsheet/Readers/XSV.h
+++ b/Userland/Applications/Spreadsheet/Readers/XSV.h
@@ -59,17 +59,18 @@ constexpr ParserBehaviour default_behaviours()
 
 class XSV {
 public:
-    XSV(StringView source, const ParserTraits& traits, ParserBehaviour behaviours = default_behaviours())
+    XSV(StringView source, ParserTraits traits, ParserBehaviour behaviours = default_behaviours())
         : m_source(source)
         , m_lexer(m_source)
         , m_traits(traits)
         , m_behaviours(behaviours)
     {
-        parse();
+        parse_preview();
     }
 
     virtual ~XSV() { }
 
+    void parse();
     bool has_error() const { return m_error != ReadError::None; }
     ReadError error() const { return m_error; }
     String error_string() const
@@ -180,8 +181,15 @@ private:
         }
     };
     void set_error(ReadError error);
-    void parse();
+    void parse_preview();
     void read_headers();
+    void reset()
+    {
+        m_lexer = GenericLexer { m_source };
+        m_rows.clear();
+        m_names.clear();
+        m_error = ReadError::None;
+    }
     Vector<Field> read_row(bool header_row = false);
     Field read_one_field();
     Field read_one_quoted_field();
@@ -189,7 +197,7 @@ private:
 
     StringView m_source;
     GenericLexer m_lexer;
-    const ParserTraits& m_traits;
+    ParserTraits m_traits;
     ParserBehaviour m_behaviours;
     Vector<Field> m_names;
     Vector<Vector<Field>> m_rows;