import json
import re
from pathlib import Path
from typing import Dict, Iterable, List, Optional, Tuple, Union

import avro.schema
import click
import pydantic
import yaml
from avrogen import write_schema_files

ENTITY_CATEGORY_UNSET = "_unset_"


class EntityType(pydantic.BaseModel):
    name: str
    doc: Optional[str] = None
    category: str = ENTITY_CATEGORY_UNSET

    keyAspect: str
    aspects: List[str]


def load_entity_registry(entity_registry_file: Path) -> List[EntityType]:
    with entity_registry_file.open() as f:
        raw_entity_registry = yaml.safe_load(f)

    entities = pydantic.parse_obj_as(List[EntityType], raw_entity_registry["entities"])
    return entities


def load_schema_file(schema_file: Union[str, Path]) -> dict:
    raw_schema_text = Path(schema_file).read_text()
    return json.loads(raw_schema_text)


def load_schemas(schemas_path: str) -> Dict[str, dict]:
    required_schema_files = {
        "mxe/MetadataChangeEvent.avsc",
        "mxe/MetadataChangeProposal.avsc",
        "usage/UsageAggregation.avsc",
        "mxe/MetadataChangeLog.avsc",
        "mxe/PlatformEvent.avsc",
        "platform/event/v1/EntityChangeEvent.avsc",
        "metadata/query/filter/Filter.avsc",  # temporarily added to test reserved keywords support
    }

    # Find all the aspect schemas / other important schemas.
    schema_files: List[Path] = []
    for schema_file in Path(schemas_path).glob("**/*.avsc"):
        relative_path = schema_file.relative_to(schemas_path).as_posix()
        if relative_path in required_schema_files:
            schema_files.append(schema_file)
            required_schema_files.remove(relative_path)
        elif load_schema_file(schema_file).get("Aspect"):
            schema_files.append(schema_file)

    assert not required_schema_files, f"Schema files not found: {required_schema_files}"

    schemas: Dict[str, dict] = {}
    for schema_file in schema_files:
        schema = load_schema_file(schema_file)
        schemas[Path(schema_file).stem] = schema

    return schemas


def patch_schemas(schemas: Dict[str, dict], pdl_path: Path) -> Dict[str, dict]:
    # We can easily find normal urn types using the generated avro schema,
    # but for arrays of urns there's nothing in the avro schema and hence
    # we have to look in the PDL files instead.
    urn_arrays: Dict[
        str, List[Tuple[str, str]]
    ] = {}  # schema name -> list of (field name, type)

    # First, we need to load the PDL files and find all urn arrays.
    for pdl_file in Path(pdl_path).glob("**/*.pdl"):
        pdl_text = pdl_file.read_text()

        # TRICKY: We assume that all urn types end with "Urn".
        arrays = re.findall(
            r"^\s*(\w+)\s*:\s*(?:optional\s+)?array\[(\w*Urn)\]",
            pdl_text,
            re.MULTILINE,
        )
        if arrays:
            schema_name = pdl_file.stem
            urn_arrays[schema_name] = [(item[0], item[1]) for item in arrays]

    # Then, we can patch each schema.
    patched_schemas = {}
    for name, schema in schemas.items():
        patched_schemas[name] = patch_schema(schema, urn_arrays)

    return patched_schemas


def patch_schema(schema: dict, urn_arrays: Dict[str, List[Tuple[str, str]]]) -> dict:
    """
    This method patches the schema to add an "Urn" property to all urn fields.
    Because the inner type in an array is not a named Avro schema, for urn arrays
    we annotate the array field and add an "urn_is_array" property.
    """

    # We're using Names() to generate a full list of embedded schemas.
    all_schemas = avro.schema.Names()
    patched = avro.schema.make_avsc_object(schema, names=all_schemas)

    for nested in all_schemas.names.values():
        if isinstance(nested, (avro.schema.EnumSchema, avro.schema.FixedSchema)):
            continue
        assert isinstance(nested, avro.schema.RecordSchema)

        # Patch normal urn types.
        field: avro.schema.Field
        for field in nested.fields:
            java_class: Optional[str] = field.props.get("java", {}).get("class")
            if java_class and java_class.startswith(
                "com.linkedin.pegasus2avro.common.urn."
            ):
                field.set_prop("Urn", java_class.split(".")[-1])

        # Patch array urn types.
        if nested.name in urn_arrays:
            mapping = urn_arrays[nested.name]

            for field_name, type in mapping:
                field = nested.fields_dict[field_name]
                field.set_prop("Urn", type)
                field.set_prop("urn_is_array", True)

    return patched.to_json()


def merge_schemas(schemas_obj: List[dict]) -> str:
    # Combine schemas as a "union" of all of the types.
    merged = ["null"] + schemas_obj

    # Patch add_name method to NOT complain about duplicate names.
    class NamesWithDups(avro.schema.Names):
        def add_name(self, name_attr, space_attr, new_schema):
            to_add = avro.schema.Name(name_attr, space_attr, self.default_namespace)
            self.names[to_add.fullname] = new_schema
            return to_add

    cleaned_schema = avro.schema.make_avsc_object(merged, names=NamesWithDups())

    # Convert back to an Avro schema JSON representation.
    out_schema = cleaned_schema.to_json()
    encoded = json.dumps(out_schema, indent=2)
    return encoded


autogen_header = """# flake8: noqa

# This file is autogenerated by /metadata-ingestion/scripts/avro_codegen.py
# Do not modify manually!

# pylint: skip-file
# fmt: off
"""
autogen_footer = """
# fmt: on
"""


def suppress_checks_in_file(filepath: Union[str, Path]) -> None:
    """
    Adds a couple lines to the top of an autogenerated file:
        - Comments to suppress flake8 and black.
        - A note stating that the file was autogenerated.
    """

    with open(filepath, "r+") as f:
        contents = f.read()

        f.seek(0, 0)
        f.write(autogen_header)
        f.write(contents)
        f.write(autogen_footer)


def add_avro_python3_warning(filepath: Path) -> None:
    contents = filepath.read_text()

    contents = f"""
# The SchemaFromJSONData method only exists in avro-python3, but is called make_avsc_object in avro.
# We can use this fact to detect conflicts between the two packages. Pip won't detect those conflicts
# because both are namespace packages, and hence are allowed to overwrite files from each other.
# This means that installation order matters, which is a pretty unintuitive outcome.
# See https://github.com/pypa/pip/issues/4625 for details.
try:
    from avro.schema import SchemaFromJSONData
    import warnings

    warnings.warn("It seems like 'avro-python3' is installed, which conflicts with the 'avro' package used by datahub. "
                + "Try running `pip uninstall avro-python3 && pip install --upgrade --force-reinstall avro` to fix this issue.")
except ImportError:
    pass

{contents}
    """

    filepath.write_text(contents)


load_schema_method = """
import functools
import pathlib

@functools.lru_cache(maxsize=None)
def _load_schema(schema_name: str) -> str:
    return (pathlib.Path(__file__).parent / f"{schema_name}.avsc").read_text()
"""
individual_schema_method = """
def get{schema_name}Schema() -> str:
    return _load_schema("{schema_name}")
"""


def make_load_schema_methods(schemas: Iterable[str]) -> str:
    return load_schema_method + "".join(
        individual_schema_method.format(schema_name=schema) for schema in schemas
    )


def save_raw_schemas(schema_save_dir: Path, schemas: Dict[str, dict]) -> None:
    # Save raw avsc files.
    schema_save_dir.mkdir()
    for name, schema in schemas.items():
        (schema_save_dir / f"{name}.avsc").write_text(json.dumps(schema, indent=2))

    # Add getXSchema methods.
    with open(schema_save_dir / "__init__.py", "w") as schema_dir_init:
        schema_dir_init.write(make_load_schema_methods(schemas.keys()))


def annotate_aspects(aspects: List[dict], schema_class_file: Path) -> None:
    schema_classes_lines = schema_class_file.read_text().splitlines()
    line_lookup_table = {line: i for i, line in enumerate(schema_classes_lines)}

    # Create the Aspect class.
    # We ensure that it cannot be instantiated directly, as
    # per https://stackoverflow.com/a/7989101/5004662.
    schema_classes_lines[
        line_lookup_table["__SCHEMAS: Dict[str, RecordSchema] = {}"]
    ] += """

class _Aspect(DictWrapper):
    ASPECT_NAME: ClassVar[str] = None  # type: ignore
    ASPECT_TYPE: ClassVar[str] = "default"
    ASPECT_INFO: ClassVar[dict] = None  # type: ignore

    def __init__(self):
        if type(self) is _Aspect:
            raise TypeError("_Aspect is an abstract class, and cannot be instantiated directly.")
        super().__init__()

    @classmethod
    def get_aspect_name(cls) -> str:
        return cls.ASPECT_NAME  # type: ignore

    @classmethod
    def get_aspect_type(cls) -> str:
        return cls.ASPECT_TYPE

    @classmethod
    def get_aspect_info(cls) -> dict:
        return cls.ASPECT_INFO
"""

    for aspect in aspects:
        className = f'{aspect["name"]}Class'
        aspectName = aspect["Aspect"]["name"]
        class_def_original = f"class {className}(DictWrapper):"

        # Make the aspects inherit from the Aspect class.
        class_def_line = line_lookup_table[class_def_original]
        schema_classes_lines[class_def_line] = f"class {className}(_Aspect):"

        # Define the ASPECT_NAME class attribute.
        # There's always an empty line between the docstring and the RECORD_SCHEMA class attribute.
        # We need to find it and insert our line of code there.
        empty_line = class_def_line + 1
        while not (
            schema_classes_lines[empty_line].strip() == ""
            and schema_classes_lines[empty_line + 1]
            .strip()
            .startswith("RECORD_SCHEMA = ")
        ):
            empty_line += 1
        schema_classes_lines[empty_line] = "\n"
        schema_classes_lines[empty_line] += f"\n    ASPECT_NAME = '{aspectName}'"
        if "type" in aspect["Aspect"]:
            schema_classes_lines[
                empty_line
            ] += f"\n    ASPECT_TYPE = '{aspect['Aspect']['type']}'"

        aspect_info = {
            k: v for k, v in aspect["Aspect"].items() if k not in {"name", "type"}
        }
        schema_classes_lines[empty_line] += f"\n    ASPECT_INFO = {aspect_info}"

        schema_classes_lines[empty_line + 1] += "\n"

    # Finally, generate a big list of all available aspects.
    newline = "\n"
    schema_classes_lines.append(
        f"""
ASPECT_CLASSES: List[Type[_Aspect]] = [
    {f',{newline}    '.join(f"{aspect['name']}Class" for aspect in aspects)}
]

KEY_ASPECTS: Dict[str, Type[_Aspect]] = {{
    {f',{newline}    '.join(f"'{aspect['Aspect']['keyForEntity']}': {aspect['name']}Class" for aspect in aspects if aspect['Aspect'].get('keyForEntity'))}
}}
"""
    )

    schema_class_file.write_text("\n".join(schema_classes_lines))


@click.command()
@click.argument(
    "entity_registry", type=click.Path(exists=True, dir_okay=False), required=True
)
@click.argument(
    "pdl_path", type=click.Path(exists=True, file_okay=False), required=True
)
@click.argument(
    "schemas_path", type=click.Path(exists=True, file_okay=False), required=True
)
@click.argument("outdir", type=click.Path(), required=True)
def generate(
    entity_registry: str, pdl_path: str, schemas_path: str, outdir: str
) -> None:
    entities = load_entity_registry(Path(entity_registry))
    schemas = load_schemas(schemas_path)

    # Patch the avsc files.
    schemas = patch_schemas(schemas, Path(pdl_path))

    # Special handling for aspects.
    aspects = {
        schema["Aspect"]["name"]: schema
        for schema in schemas.values()
        if schema.get("Aspect")
    }

    for entity in entities:
        # This implicitly requires that all keyAspects are resolvable.
        aspect = aspects[entity.keyAspect]

        # This requires that entities cannot share a keyAspect.
        if (
            "keyForEntity" in aspect["Aspect"]
            and aspect["Aspect"]["keyForEntity"] != entity.name
        ):
            raise ValueError(
                f'Entity key {entity.keyAspect} is used by {aspect["Aspect"]["keyForEntity"]} and {entity.name}'
            )

        aspect["Aspect"]["keyForEntity"] = entity.name
        aspect["Aspect"]["entityCategory"] = entity.category
        aspect["Aspect"]["entityAspects"] = entity.aspects
        if entity.doc is not None:
            aspect["Aspect"]["entityDoc"] = entity.doc

    # Check for unused aspects. We currently have quite a few.
    # unused_aspects = set(aspects.keys()) - set().union(
    #     {entity.keyAspect for entity in entities},
    #     *(set(entity.aspects) for entity in entities),
    # )

    merged_schema = merge_schemas(list(schemas.values()))
    write_schema_files(merged_schema, outdir)

    # Schema files post-processing.
    (Path(outdir) / "__init__.py").write_text("# This file is intentionally empty.\n")
    add_avro_python3_warning(Path(outdir) / "schema_classes.py")
    annotate_aspects(
        list(aspects.values()),
        Path(outdir) / "schema_classes.py",
    )

    # Keep a copy of a few raw avsc files.
    required_avsc_schemas = {"MetadataChangeEvent", "MetadataChangeProposal"}
    schema_save_dir = Path(outdir) / "schemas"
    save_raw_schemas(
        schema_save_dir,
        {
            name: schema
            for name, schema in schemas.items()
            if name in required_avsc_schemas
        },
    )

    # Add headers for all generated files
    generated_files = Path(outdir).glob("**/*.py")
    for file in generated_files:
        suppress_checks_in_file(file)


if __name__ == "__main__":
    generate()