Add feature parity with go-cid implementation

cid/__init__.py

@@ -4,4 +4,20 @@
 __email__ = "dhruv@dhruvb.com"
 __version__ = "0.4.0"
 
-from .cid import CIDv0, CIDv1, from_bytes, from_string, is_cid, make_cid  # noqa: F401
+from .cid import (  # noqa: F401
+    CIDJSONEncoder,
+    CIDv0,
+    CIDv1,
+    extract_encoding,
+    from_bytes,
+    from_bytes_strict,
+    from_reader,
+    from_string,
+    is_cid,
+    make_cid,
+    must_parse,
+    parse_ipfs_path,
+)
+from .builder import Builder, V0Builder, V1Builder  # noqa: F401
+from .prefix import Prefix  # noqa: F401
+from .set import CIDSet  # noqa: F401

cid/builder.py

@@ -0,0 +1,147 @@
+"""Builder pattern for CID construction."""
+
+from abc import ABC, abstractmethod
+import hashlib
+from typing import TYPE_CHECKING
+
+import multihash
+
+if TYPE_CHECKING:
+    from .cid import CIDv0, CIDv1
+
+
+class Builder(ABC):
+    """Builder interface for CID construction."""
+
+    @abstractmethod
+    def sum(self, data: bytes) -> "CIDv0 | CIDv1":
+        """
+        Hash data and create CID.
+
+        :param bytes data: Data to hash
+        :return: CID object
+        :rtype: :py:class:`cid.CIDv0` or :py:class:`cid.CIDv1`
+        """
+        pass
+
+    @abstractmethod
+    def get_codec(self) -> str:
+        """
+        Get current codec.
+
+        :return: Codec name
+        :rtype: str
+        """
+        pass
+
+    @abstractmethod
+    def with_codec(self, codec: str) -> "Builder":
+        """
+        Return new builder with different codec.
+
+        :param str codec: New codec name
+        :return: New builder instance
+        :rtype: :py:class:`cid.builder.Builder`
+        """
+        pass
+
+
+class V0Builder(Builder):
+    """Builder for CIDv0."""
+
+    def sum(self, data: bytes) -> "CIDv0":
+        """
+        Create CIDv0 from data.
+
+        :param bytes data: Data to hash
+        :return: CIDv0 object
+        :rtype: :py:class:`cid.CIDv0`
+        """
+        from .cid import CIDv0
+
+        digest = hashlib.sha256(data).digest()
+        mhash = multihash.encode(digest, "sha2-256")
+        return CIDv0(mhash)
+
+    def get_codec(self) -> str:
+        """
+        Get current codec (always "dag-pb" for CIDv0).
+
+        :return: Codec name
+        :rtype: str
+        """
+        return "dag-pb"
+
+    def with_codec(self, codec: str) -> Builder:
+        """
+        Return new builder with different codec.
+
+        Changing codec from CIDv0 requires switching to V1Builder.
+
+        :param str codec: New codec name
+        :return: New builder instance (V1Builder if codec changed)
+        :rtype: :py:class:`cid.builder.Builder`
+        """
+        if codec == "dag-pb":
+            return self
+        # Changing codec requires V1
+        return V1Builder(codec=codec, mh_type="sha2-256")
+
+
+class V1Builder(Builder):
+    """Builder for CIDv1."""
+
+    def __init__(self, codec: str, mh_type: str, mh_length: int = -1) -> None:
+        """
+        Create V1Builder.
+
+        :param str codec: Codec name
+        :param str mh_type: Multihash type
+        :param int mh_length: Multihash length (-1 for default)
+        """
+        self.codec = codec
+        self.mh_type = mh_type
+        self.mh_length = mh_length
+
+    def sum(self, data: bytes) -> "CIDv1":
+        """
+        Create CIDv1 from data.
+
+        :param bytes data: Data to hash
+        :return: CIDv1 object
+        :rtype: :py:class:`cid.CIDv1`
+        """
+        from .cid import CIDv1
+
+        if self.mh_type == "sha2-256":
+            digest = hashlib.sha256(data).digest()
+        elif self.mh_type == "sha2-512":
+            digest = hashlib.sha512(data).digest()
+        else:
+            msg = f"Hash type {self.mh_type} not fully implemented"
+            raise NotImplementedError(msg)
+
+        mh_length = None if self.mh_length == -1 else self.mh_length
+        mhash = multihash.encode(digest, self.mh_type, mh_length)
+        return CIDv1(self.codec, mhash)
+
+    def get_codec(self) -> str:
+        """
+        Get current codec.
+
+        :return: Codec name
+        :rtype: str
+        """
+        return self.codec
+
+    def with_codec(self, codec: str) -> Builder:
+        """
+        Return new builder with different codec.
+
+        :param str codec: New codec name
+        :return: New builder instance
+        :rtype: :py:class:`cid.builder.Builder`
+        """
+        if codec == self.codec:
+            return self
+        return V1Builder(codec=codec, mh_type=self.mh_type, mh_length=self.mh_length)