1 files changed, 145 insertions, 0 deletions
diff --git a/Applications/Calculator/Keypad.cpp b/Applications/Calculator/Keypad.cpp
new file mode 100644
index 0000000000..14af878138
--- /dev/null
+++ b/Applications/Calculator/Keypad.cpp
@@ -0,0 +1,145 @@
+#include "Keypad.h"
+#include <AK/StringBuilder.h>
+#include <math.h>
+
+Keypad::Keypad()
+{
+}
+
+Keypad::~Keypad()
+{
+}
+
+void Keypad::type_digit(int digit)
+{
+    switch (m_state) {
+    case State::External:
+        m_state = State::TypingInteger;
+        m_negative = false;
+        m_int_value = digit;
+        m_frac_value = 0;
+        m_frac_length = 0;
+        break;
+    case State::TypingInteger:
+        ASSERT(m_frac_value == 0);
+        ASSERT(m_frac_length == 0);
+        m_int_value *= 10;
+        m_int_value += digit;
+        break;
+    case State::TypingDecimal:
+        if (m_frac_length > 6)
+            break;
+        m_frac_value *= 10;
+        m_frac_value += digit;
+        m_frac_length++;
+        break;
+    }
+}
+
+void Keypad::type_decimal_point()
+{
+    switch (m_state) {
+    case State::External:
+        m_negative = false;
+        m_int_value = 0;
+        m_frac_value = 0;
+        m_frac_length = 0;
+        break;
+    case State::TypingInteger:
+        ASSERT(m_frac_value == 0);
+        ASSERT(m_frac_length == 0);
+        m_state = State::TypingDecimal;
+        break;
+    case State::TypingDecimal:
+        // Ignore it.
+        break;
+    }
+}
+
+void Keypad::type_backspace()
+{
+    switch (m_state) {
+    case State::External:
+        m_negative = false;
+        m_int_value = 0;
+        m_frac_value = 0;
+        m_frac_length = 0;
+        break;
+    case State::TypingDecimal:
+        if (m_frac_length > 0) {
+            m_frac_value /= 10;
+            m_frac_length--;
+            break;
+        }
+        ASSERT(m_frac_value == 0);
+        m_state = State::TypingInteger;
+        [[fallthrough]];
+    case State::TypingInteger:
+        ASSERT(m_frac_value == 0);
+        ASSERT(m_frac_length == 0);
+        m_int_value /= 10;
+        if (m_int_value == 0)
+            m_negative = false;
+        break;
+    }
+}
+
+double Keypad::value() const
+{
+    double res = 0.0;
+
+    long frac = m_frac_value;
+    for (int i = 0; i < m_frac_length; i++) {
+        int digit = frac % 10;
+        res += digit;
+        res /= 10.0;
+        frac /= 10;
+    }
+
+    res += m_int_value;
+    if (m_negative)
+        res = -res;
+
+    return res;
+}
+
+void Keypad::set_value(double value)
+{
+    m_state = State::External;
+
+    if (value < 0.0) {
+        m_negative = true;
+        value = -value;
+    } else
+        m_negative = false;
+
+    m_int_value = value;
+    value -= m_int_value;
+
+    m_frac_value = 0;
+    m_frac_length = 0;
+    while (value != 0) {
+        value *= 10.0;
+        int digit = value;
+        m_frac_value *= 10;
+        m_frac_value += digit;
+        m_frac_length++;
+        value -= digit;
+
+        if (m_frac_length > 6)
+            break;
+    }
+}
+
+String Keypad::to_string() const
+{
+    StringBuilder builder;
+    if (m_negative)
+        builder.append("-");
+    builder.appendf("%ld.", m_int_value);
+
+    if (m_frac_length > 0)
+        builder.appendf("%0*ld", m_frac_length, m_frac_value);
+
+    return builder.to_string();
+}