import logging
import os
import urllib.parse as urlparse
from collections.abc import Callable
from typing import Any, TypedDict

DEFAULT_ENV = "DATABASE_URL"
ENGINE_SCHEMES: dict[str, "Engine"] = {}

MYSQL_BACKEND = "django.db.backends.mysql"
MYSQL_GIS_BACKEND = "django.contrib.gis.db.backends.mysql"
POSTGRESQL_BACKEND = "django.db.backends.postgresql"
POSTGIS_BACKEND = "django.contrib.gis.db.backends.postgis"
REDSHIFT_BACKEND = "django_redshift_backend"
COCKROACH_BACKEND = "django_cockroachdb"
TIMESCALE_BACKEND = "timescale.db.backends.postgresql"
TIMESCALE_GIS_BACKEND = "timescale.db.backends.postgis"
MSSQL_BACKEND = "mssql"
MSSQL_PYODBC_BACKEND = "sql_server.pyodbc"
SQLITE_BACKEND = "django.db.backends.sqlite3"
SPATIALITE_GIS_BACKEND = "django.contrib.gis.db.backends.spatialite"
ORACLE_BACKEND = "django.db.backends.oracle"
ORACLE_GIS_BACKEND = "django.contrib.gis.db.backends.oracle"
MYSQL_CONNECTOR_BACKEND = "mysql.connector.django"

MYSQL_BACKENDS = (
    MYSQL_BACKEND,
    MYSQL_GIS_BACKEND,
)
POSTGRES_BACKENDS = (
    POSTGRESQL_BACKEND,
    POSTGIS_BACKEND,
    REDSHIFT_BACKEND,
    COCKROACH_BACKEND,
    TIMESCALE_BACKEND,
    TIMESCALE_GIS_BACKEND,
)
MSSQL_BACKENDS = (
    MSSQL_BACKEND,
    MSSQL_PYODBC_BACKEND,
)


# From https://docs.djangoproject.com/en/stable/ref/settings/#databases
class DBConfig(TypedDict, total=False):
    ATOMIC_REQUESTS: bool
    AUTOCOMMIT: bool
    CONN_MAX_AGE: int | None
    CONN_HEALTH_CHECKS: bool
    DISABLE_SERVER_SIDE_CURSORS: bool
    ENGINE: str
    HOST: str
    NAME: str
    OPTIONS: dict[str, Any]
    PASSWORD: str
    PORT: str | int
    TEST: dict[str, Any]
    TIME_ZONE: str
    USER: str


PostprocessCallable = Callable[[DBConfig], None]
OptionType = int | str | bool


class ParseError(ValueError):
    def __str__(self) -> str:
        return (
            "This string is not a valid url, possibly because some of its parts"
            " is not properly urllib.parse.quote()'ed."
        )


class UnknownSchemeError(ValueError):
    def __init__(self, scheme: str):
        self.scheme = scheme

    def __str__(self) -> str:
        schemes = ", ".join(sorted(ENGINE_SCHEMES.keys()))
        return (
            f"Scheme '{self.scheme}://' is unknown."
            " Did you forget to register custom backend?"
            f" Following schemes have registered backends: {schemes}."
        )


def default_postprocess(parsed_config: DBConfig) -> None:
    pass


class Engine:
    def __init__(
        self,
        backend: str,
        postprocess: PostprocessCallable = default_postprocess,
    ):
        self.backend = backend
        self.postprocess = postprocess


def register(
    scheme: str, backend: str
) -> Callable[[PostprocessCallable], PostprocessCallable]:
    engine = Engine(backend)
    if scheme not in ENGINE_SCHEMES:
        urlparse.uses_netloc.append(scheme)
    ENGINE_SCHEMES[scheme] = engine

    def inner(func: PostprocessCallable) -> PostprocessCallable:
        engine.postprocess = func
        return func

    return inner


register("spatialite", SPATIALITE_GIS_BACKEND)
register("mysql-connector", MYSQL_CONNECTOR_BACKEND)
register("mysqlgis", MYSQL_GIS_BACKEND)
register("oraclegis", ORACLE_GIS_BACKEND)
register("cockroach", COCKROACH_BACKEND)


@register("sqlite", SQLITE_BACKEND)
def default_to_in_memory_db(parsed_config: DBConfig) -> None:
    # mimic sqlalchemy behaviour
    if not parsed_config.get("NAME"):
        parsed_config["NAME"] = ":memory:"


@register("oracle", ORACLE_BACKEND)
@register("mssqlms", MSSQL_BACKEND)
@register("mssql", MSSQL_PYODBC_BACKEND)
def stringify_port(parsed_config: DBConfig) -> None:
    parsed_config["PORT"] = str(parsed_config.get("PORT", ""))


@register("mysql", MYSQL_BACKEND)
@register("mysql2", MYSQL_BACKEND)
def apply_ssl_ca(parsed_config: DBConfig) -> None:
    options = parsed_config.get("OPTIONS", {})
    ca = options.pop("ssl-ca", None)
    if ca:
        options["ssl"] = {"ca": ca}


@register("postgres", POSTGRESQL_BACKEND)
@register("postgresql", POSTGRESQL_BACKEND)
@register("pgsql", POSTGRESQL_BACKEND)
@register("postgis", POSTGIS_BACKEND)
@register("redshift", REDSHIFT_BACKEND)
@register("timescale", TIMESCALE_BACKEND)
@register("timescalegis", TIMESCALE_GIS_BACKEND)
def apply_current_schema(parsed_config: DBConfig) -> None:
    options = parsed_config.get("OPTIONS", {})
    schema = options.pop("currentSchema", None)
    if schema:
        options["options"] = f"-c search_path={schema}"


def config(
    env: str = DEFAULT_ENV,
    default: str | None = None,
    engine: str | None = None,
    conn_max_age: int | None = 0,
    conn_health_checks: bool = False,
    disable_server_side_cursors: bool = False,
    ssl_require: bool = False,
    test_options: dict[str, Any] | None = None,
) -> DBConfig:
    """Returns configured DATABASE dictionary from DATABASE_URL."""
    s = os.environ.get(env, default)

    if s is None:
        logging.warning(
            "No %s environment variable set, and so no databases setup", env
        )

    if s:
        return parse(
            s,
            engine,
            conn_max_age,
            conn_health_checks,
            disable_server_side_cursors,
            ssl_require,
            test_options,
        )

    return {}


def parse(
    url: str,
    engine: str | None = None,
    conn_max_age: int | None = 0,
    conn_health_checks: bool = False,
    disable_server_side_cursors: bool = False,
    ssl_require: bool = False,
    test_options: dict[str, Any] | None = None,
) -> DBConfig:
    """Parses a database URL and returns configured DATABASE dictionary."""
    settings = _convert_to_settings(
        engine,
        conn_max_age,
        conn_health_checks,
        disable_server_side_cursors,
        test_options,
    )

    if url == "sqlite://:memory:":
        # this is a special case, because if we pass this URL into
        # urlparse, urlparse will choke trying to interpret "memory"
        # as a port number
        return {"ENGINE": ENGINE_SCHEMES["sqlite"].backend, "NAME": ":memory:"}
        # note: no other settings are required for sqlite

    try:
        split_result = urlparse.urlsplit(url)
        engine_obj = ENGINE_SCHEMES.get(split_result.scheme)
        if engine_obj is None:
            raise UnknownSchemeError(split_result.scheme)
        path = split_result.path[1:]
        query = urlparse.parse_qs(split_result.query)
        options = {k: _parse_option_values(v) for k, v in query.items()}
        parsed_config: DBConfig = {
            "ENGINE": engine_obj.backend,
            "USER": urlparse.unquote(split_result.username or ""),
            "PASSWORD": urlparse.unquote(split_result.password or ""),
            "HOST": urlparse.unquote(split_result.hostname or ""),
            "PORT": split_result.port or "",
            "NAME": urlparse.unquote(path),
            "OPTIONS": options,
        }
    except UnknownSchemeError:
        raise
    except ValueError:
        raise ParseError() from None

    # Guarantee that config has options, possibly empty, when postprocess() is called
    assert isinstance(parsed_config["OPTIONS"], dict)
    engine_obj.postprocess(parsed_config)

    # Update the final config with any settings passed in explicitly.
    parsed_config["OPTIONS"].update(settings.pop("OPTIONS", {}))
    parsed_config.update(settings)

    if ssl_require:
        _configure_ssl(parsed_config)

    if not parsed_config["OPTIONS"]:
        parsed_config.pop("OPTIONS")
    return parsed_config


def _parse_option_values(values: list[str]) -> OptionType | list[OptionType]:
    parsed_values = [_parse_value(v) for v in values]
    return parsed_values[0] if len(parsed_values) == 1 else parsed_values


def _parse_value(value: str) -> OptionType:
    if value.isdigit():
        return int(value)
    if value.lower() in ("true", "false"):
        return value.lower() == "true"
    return value


def _configure_ssl(parsed_config: DBConfig) -> None:
    assert "OPTIONS" in parsed_config
    options = parsed_config["OPTIONS"]
    assert "ENGINE" in parsed_config
    backend = parsed_config["ENGINE"]

    if backend in MYSQL_BACKENDS:
        options["ssl_mode"] = "REQUIRED"
    elif backend in POSTGRES_BACKENDS:
        options["sslmode"] = "require"
    elif backend in MSSQL_BACKENDS:
        current_extra = options.get("extra_params", "")
        if "Encrypt=yes" not in current_extra:
            if current_extra:
                options["extra_params"] = f"{current_extra};Encrypt=yes"
            else:
                options["extra_params"] = "Encrypt=yes"


def _convert_to_settings(
    engine: str | None,
    conn_max_age: int | None,
    conn_health_checks: bool,
    disable_server_side_cursors: bool,
    test_options: dict[str, Any] | None,
) -> DBConfig:
    settings: DBConfig = {
        "CONN_MAX_AGE": conn_max_age,
        "CONN_HEALTH_CHECKS": conn_health_checks,
        "DISABLE_SERVER_SIDE_CURSORS": disable_server_side_cursors,
    }
    if engine:
        settings["ENGINE"] = engine
    if test_options:
        settings["TEST"] = test_options
    return settings