feat(fstring): implement basic number formatting

examples/basic/23_format_spec.peb

@@ -1,9 +1,23 @@
+// Basic type
 let a = 42
 print(f"int: {a:d}; hex: {a:x}; HEX: {a:X}; oct: {a:o}; bin: {a:b}")
+
+// Grouping
 let b = 1234567890
 print(f"{b:,}")
 print(f"{b:_}")
 
+let c = 1234.5678
+print(f"{c:,._}")
+print(f"{c:_.,}")
+
+// Sign
+
+// Percentage
 let pts = 19
 let total = 22
 print(f"Correct answers: {pts/total:.2%}")
+
+// Precision
+
+// Complex

src/core/format_spec/string_formatter.py

@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from src.core.format_spec.spec import FormatSpec
 from src.core.format_spec.token import TokenType, Token
@@ -21,10 +21,134 @@ class StringFormatter:
         return obj
 
     @staticmethod
-    def check_type(token: Token, obj: Any, expected_type: type | tuple[type, ...]):
+    def assert_type(token: Token, obj: Any, expected_type: type | tuple[type, ...]):
         if not isinstance(obj, expected_type):
             raise PebbleRuntimeError(token, f"Invalid value type. Expected {expected_type}, got {type(obj)}")
 
+    def check_type(self, obj: Any, fmt_type_token: Token) -> Any:
+        match fmt_type_token.type:
+            case TokenType.T_STR:
+                self.assert_type(fmt_type_token, obj, str)
+
+            case TokenType.T_BIN | TokenType.T_DEC | TokenType.T_HEX | TokenType.T_HEX_CAPS | TokenType.T_OCT:
+                if isinstance(obj, float) and obj.is_integer():
+                    obj = int(obj)
+                self.assert_type(fmt_type_token, obj, int)
+
+            case TokenType.T_SCI | TokenType.T_FIX | TokenType.T_PCT:
+                if isinstance(obj, int):
+                    obj = float(obj)
+                self.assert_type(fmt_type_token, obj, float)
+
+            case _:
+                raise PebbleRuntimeError(fmt_type_token, f"Unsupported formatting type '{fmt_type_token.lexeme}'.")
+        return obj
+
+    def guess_type(self, obj: Any) -> tuple[Optional[TokenType], Any]:
+        fmt_type: Optional[TokenType] = None
+        if isinstance(obj, str):
+            fmt_type = TokenType.T_STR
+        elif isinstance(obj, int):
+            fmt_type = TokenType.T_DEC
+        elif isinstance(obj, float):
+            if obj.is_integer():
+                obj = int(obj)
+                fmt_type = TokenType.T_DEC
+            else:
+                fmt_type = TokenType.T_FIX
+        return fmt_type, obj
+
     def format(self, obj: Any, spec: FormatSpec) -> str:
-        # TODO
-        return str(obj)
+        res: str = ""
+        fmt_type: Optional[TokenType]
+        fmt_type_token: Optional[Token]
+        if spec.type is not None:
+            obj = self.check_type(obj, spec.type)
+            fmt_type = spec.type.type
+        else:
+            fmt_type, obj = self.guess_type(obj)
+
+        match fmt_type:
+            case None:
+                res = self.stringify(obj)
+            case TokenType.T_STR:
+                res = obj
+            case TokenType.T_BIN | TokenType.T_DEC | TokenType.T_HEX | TokenType.T_HEX_CAPS | TokenType.T_OCT:
+                res = self.format_int(obj, spec, fmt_type)
+            case TokenType.T_SCI | TokenType.T_FIX | TokenType.T_PCT:
+                res = self.format_float(obj, spec, fmt_type)
+
+        if spec.number.integral.width is not None:
+            res = self.pad(res, spec.number.integral.width)
+        return res
+
+    def format_int(self, value: int, spec: FormatSpec, fmt_type: TokenType) -> str:
+        if spec.number.decimal is not None:
+            raise PebbleRuntimeError(spec.number.decimal.dot, "Incompatible decimal options with int type.")
+
+        sign: str = self.make_sign(value, spec)
+        string: str = self.format_int_part(value, fmt_type, spec.number.integral.grouping)
+
+        return sign + string
+
+    def format_float(self, value: float, spec: FormatSpec, fmt_type: TokenType) -> str:
+        sign: str = self.make_sign(value, spec)
+        value = abs(value)
+        integer: int = int(value)
+        decimal: float = value - integer
+        integer_spec = spec.number.integral
+        decimal_spec = spec.number.decimal
+
+        if decimal_spec is not None:
+            if decimal_spec.precision is not None:
+                decimal = round(decimal, decimal_spec.precision)
+
+        integer_str: str = self.format_int_part(integer, fmt_type, integer_spec.grouping)
+        decimal_str: str = self.format_int_part(int(str(decimal)[2:]), fmt_type, None if decimal_spec is None else decimal_spec.grouping)
+        if decimal_str:
+            decimal_str = f".{decimal_str}"
+
+        return f"{sign}{integer_str}{decimal_str}"
+
+    def format_int_part(self, value: int, fmt_type: TokenType, grouping: Optional[Token]):
+        groups: int = 4
+        string: str = str(value)
+        match fmt_type:
+            case TokenType.T_BIN:
+                string = f"{value:b}"
+            case TokenType.T_HEX:
+                string = f"{value:x}"
+            case TokenType.T_HEX_CAPS:
+                string = f"{value:X}"
+            case TokenType.T_OCT:
+                string = f"{value:o}"
+            case _:
+                groups = 3
+
+        if grouping is not None:
+            string = self.make_groups(string, groups, grouping.lexeme)
+        return string
+
+    def make_sign(self, value: int | float, spec: FormatSpec) -> str:
+        sign: Optional[Token] = spec.options.sign
+        plus: str = ""
+        if sign is not None:
+            match sign.type:
+                case TokenType.PLUS:
+                    plus = "+"
+                case TokenType.SPACE:
+                    plus = " "
+        return "-" if value < 0 else plus
+
+    def make_groups(self, string: str, group_size: int, sep: str) -> str:
+        groups: list[str] = []
+        length: int = len(string)
+        for i in range(0, length, group_size):
+            groups.append(string[max(0, length - i - group_size):length - i])
+        return sep.join(reversed(groups))
+
+    def pad(self, string: str, width: int) -> str:
+        to_pad: int = width - len(string)
+        if to_pad > 0:
+            string = " " * to_pad + string
+        return string