import json
from functools import lru_cache, partial

from django.conf import settings
from django.db.backends.base.operations import BaseDatabaseOperations
from django.db.backends.postgresql.compiler import InsertUnnest
from django.db.backends.postgresql.psycopg_any import (
    Inet,
    Jsonb,
    errors,
    is_psycopg3,
    mogrify,
)
from django.db.backends.utils import split_tzname_delta
from django.db.models.constants import OnConflict
from django.db.models.functions import Cast
from django.utils.regex_helper import _lazy_re_compile


@lru_cache
def get_json_dumps(encoder):
    if encoder is None:
        return json.dumps
    return partial(json.dumps, cls=encoder)


class DatabaseOperations(BaseDatabaseOperations):
    compiler_module = "django.db.backends.postgresql.compiler"
    cast_char_field_without_max_length = "varchar"
    explain_prefix = "EXPLAIN"
    explain_options = frozenset(
        [
            "ANALYZE",
            "BUFFERS",
            "COSTS",
            "GENERIC_PLAN",
            "MEMORY",
            "SETTINGS",
            "SERIALIZE",
            "SUMMARY",
            "TIMING",
            "VERBOSE",
            "WAL",
        ]
    )
    cast_data_types = {
        "AutoField": "integer",
        "BigAutoField": "bigint",
        "SmallAutoField": "smallint",
    }

    if is_psycopg3:
        from psycopg.types import numeric

        integerfield_type_map = {
            "SmallIntegerField": numeric.Int2,
            "IntegerField": numeric.Int4,
            "BigIntegerField": numeric.Int8,
            "PositiveSmallIntegerField": numeric.Int2,
            "PositiveIntegerField": numeric.Int4,
            "PositiveBigIntegerField": numeric.Int8,
        }

    def unification_cast_sql(self, output_field):
        internal_type = output_field.get_internal_type()
        if internal_type in (
            "GenericIPAddressField",
            "IPAddressField",
            "TimeField",
            "UUIDField",
        ):
            # PostgreSQL will resolve a union as type 'text' if input types are
            # 'unknown'.
            # https://www.postgresql.org/docs/current/typeconv-union-case.html
            # These fields cannot be implicitly cast back in the default
            # PostgreSQL configuration so we need to explicitly cast them.
            # We must also remove components of the type within brackets:
            # varchar(255) -> varchar.
            return (
                "CAST(%%s AS %s)" % output_field.db_type(self.connection).split("(")[0]
            )
        return "%s"

    # EXTRACT format cannot be passed in parameters.
    _extract_format_re = _lazy_re_compile(r"[A-Z_]+")

    def date_extract_sql(self, lookup_type, sql, params):
        # https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
        if lookup_type == "week_day":
            # For consistency across backends, we return Sunday=1, Saturday=7.
            return f"EXTRACT(DOW FROM {sql}) + 1", params
        elif lookup_type == "iso_week_day":
            return f"EXTRACT(ISODOW FROM {sql})", params
        elif lookup_type == "iso_year":
            return f"EXTRACT(ISOYEAR FROM {sql})", params

        lookup_type = lookup_type.upper()
        if not self._extract_format_re.fullmatch(lookup_type):
            raise ValueError(f"Invalid lookup type: {lookup_type!r}")
        return f"EXTRACT({lookup_type} FROM {sql})", params

    def date_trunc_sql(self, lookup_type, sql, params, tzname=None):
        sql, params = self._convert_sql_to_tz(sql, params, tzname)
        # https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
        return f"DATE_TRUNC(%s, {sql})", (lookup_type, *params)

    def _prepare_tzname_delta(self, tzname):
        tzname, sign, offset = split_tzname_delta(tzname)
        if offset:
            sign = "-" if sign == "+" else "+"
            return f"{tzname}{sign}{offset}"
        return tzname

    def _convert_sql_to_tz(self, sql, params, tzname):
        if tzname and settings.USE_TZ:
            tzname_param = self._prepare_tzname_delta(tzname)
            return f"{sql} AT TIME ZONE %s", (*params, tzname_param)
        return sql, params

    def datetime_cast_date_sql(self, sql, params, tzname):
        sql, params = self._convert_sql_to_tz(sql, params, tzname)
        return f"({sql})::date", params

    def datetime_cast_time_sql(self, sql, params, tzname):
        sql, params = self._convert_sql_to_tz(sql, params, tzname)
        return f"({sql})::time", params

    def datetime_extract_sql(self, lookup_type, sql, params, tzname):
        sql, params = self._convert_sql_to_tz(sql, params, tzname)
        if lookup_type == "second":
            # Truncate fractional seconds.
            return f"EXTRACT(SECOND FROM DATE_TRUNC(%s, {sql}))", ("second", *params)
        return self.date_extract_sql(lookup_type, sql, params)

    def datetime_trunc_sql(self, lookup_type, sql, params, tzname):
        sql, params = self._convert_sql_to_tz(sql, params, tzname)
        # https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
        return f"DATE_TRUNC(%s, {sql})", (lookup_type, *params)

    def time_extract_sql(self, lookup_type, sql, params):
        if lookup_type == "second":
            # Truncate fractional seconds.
            return f"EXTRACT(SECOND FROM DATE_TRUNC(%s, {sql}))", ("second", *params)
        return self.date_extract_sql(lookup_type, sql, params)

    def time_trunc_sql(self, lookup_type, sql, params, tzname=None):
        sql, params = self._convert_sql_to_tz(sql, params, tzname)
        return f"DATE_TRUNC(%s, {sql})::time", (lookup_type, *params)

    def deferrable_sql(self):
        return " DEFERRABLE INITIALLY DEFERRED"

    def bulk_insert_sql(self, fields, placeholder_rows):
        if isinstance(placeholder_rows, InsertUnnest):
            return f"SELECT * FROM {placeholder_rows}"
        return super().bulk_insert_sql(fields, placeholder_rows)

    def lookup_cast(self, lookup_type, internal_type=None):
        lookup = "%s"
        # Cast text lookups to text to allow things like filter(x__contains=4)
        if lookup_type in (
            "iexact",
            "contains",
            "icontains",
            "startswith",
            "istartswith",
            "endswith",
            "iendswith",
            "regex",
            "iregex",
        ):
            if internal_type in ("IPAddressField", "GenericIPAddressField"):
                lookup = "HOST(%s)"
            else:
                lookup = "%s::text"

        # Use UPPER(x) for case-insensitive lookups; it's faster.
        if lookup_type in ("iexact", "icontains", "istartswith", "iendswith"):
            lookup = "UPPER(%s)" % lookup

        return lookup

    def no_limit_value(self):
        return None

    def prepare_sql_script(self, sql):
        return [sql]

    def quote_name(self, name):
        if name.startswith('"') and name.endswith('"'):
            return name  # Quoting once is enough.
        return '"%s"' % name

    def compose_sql(self, sql, params):
        return mogrify(sql, params, self.connection)

    def set_time_zone_sql(self):
        return "SELECT set_config('TimeZone', %s, false)"

    def sql_flush(self, style, tables, *, reset_sequences=False, allow_cascade=False):
        if not tables:
            return []

        # Perform a single SQL 'TRUNCATE x, y, z...;' statement. It allows us
        # to truncate tables referenced by a foreign key in any other table.
        sql_parts = [
            style.SQL_KEYWORD("TRUNCATE"),
            ", ".join(style.SQL_FIELD(self.quote_name(table)) for table in tables),
        ]
        if reset_sequences:
            sql_parts.append(style.SQL_KEYWORD("RESTART IDENTITY"))
        if allow_cascade:
            sql_parts.append(style.SQL_KEYWORD("CASCADE"))
        return ["%s;" % " ".join(sql_parts)]

    def sequence_reset_by_name_sql(self, style, sequences):
        # 'ALTER SEQUENCE sequence_name RESTART WITH 1;'... style SQL
        # statements to reset sequence indices
        sql = []
        for sequence_info in sequences:
            table_name = sequence_info["table"]
            # 'id' will be the case if it's an m2m using an autogenerated
            # intermediate table (see BaseDatabaseIntrospection.sequence_list).
            column_name = sequence_info["column"] or "id"
            sql.append(
                "%s setval(pg_get_serial_sequence('%s','%s'), 1, false);"
                % (
                    style.SQL_KEYWORD("SELECT"),
                    style.SQL_TABLE(self.quote_name(table_name)),
                    style.SQL_FIELD(column_name),
                )
            )
        return sql

    def tablespace_sql(self, tablespace, inline=False):
        if inline:
            return "USING INDEX TABLESPACE %s" % self.quote_name(tablespace)
        else:
            return "TABLESPACE %s" % self.quote_name(tablespace)

    def sequence_reset_sql(self, style, model_list):
        from django.db import models

        output = []
        qn = self.quote_name
        for model in model_list:
            # Use `coalesce` to set the sequence for each model to the max pk
            # value if there are records, or 1 if there are none. Set the
            # `is_called` property (the third argument to `setval`) to true if
            # there are records (as the max pk value is already in use),
            # otherwise set it to false. Use pg_get_serial_sequence to get the
            # underlying sequence name from the table name and column name.

            for f in model._meta.local_fields:
                if isinstance(f, models.AutoField):
                    output.append(
                        "%s setval(pg_get_serial_sequence('%s','%s'), "
                        "coalesce(max(%s), 1), max(%s) %s null) %s %s;"
                        % (
                            style.SQL_KEYWORD("SELECT"),
                            style.SQL_TABLE(qn(model._meta.db_table)),
                            style.SQL_FIELD(f.column),
                            style.SQL_FIELD(qn(f.column)),
                            style.SQL_FIELD(qn(f.column)),
                            style.SQL_KEYWORD("IS NOT"),
                            style.SQL_KEYWORD("FROM"),
                            style.SQL_TABLE(qn(model._meta.db_table)),
                        )
                    )
                    # Only one AutoField is allowed per model, so don't bother
                    # continuing.
                    break
        return output

    def prep_for_iexact_query(self, x):
        return x

    def max_name_length(self):
        """
        Return the maximum length of an identifier.

        The maximum length of an identifier is 63 by default, but can be
        changed by recompiling PostgreSQL after editing the NAMEDATALEN
        macro in src/include/pg_config_manual.h.

        This implementation returns 63, but can be overridden by a custom
        database backend that inherits most of its behavior from this one.
        """
        return 63

    def distinct_sql(self, fields, params):
        if fields:
            params = [param for param_list in params for param in param_list]
            return (["DISTINCT ON (%s)" % ", ".join(fields)], params)
        else:
            return ["DISTINCT"], []

    if is_psycopg3:

        def last_executed_query(self, cursor, sql, params):
            if self.connection.features.uses_server_side_binding:
                try:
                    return self.compose_sql(sql, params)
                except errors.DataError:
                    return None
            else:
                if cursor._query and cursor._query.query is not None:
                    return cursor._query.query.decode()
                return None

    else:

        def last_executed_query(self, cursor, sql, params):
            # https://www.psycopg.org/docs/cursor.html#cursor.query
            # The query attribute is a Psycopg extension to the DB API 2.0.
            if cursor.query is not None:
                return cursor.query.decode()
            return None

    if is_psycopg3:

        def adapt_integerfield_value(self, value, internal_type):
            if value is None or hasattr(value, "resolve_expression"):
                return value
            return self.integerfield_type_map[internal_type](value)

    def adapt_datefield_value(self, value):
        return value

    def adapt_datetimefield_value(self, value):
        return value

    def adapt_timefield_value(self, value):
        return value

    def adapt_ipaddressfield_value(self, value):
        if value:
            return Inet(value)
        return None

    def adapt_json_value(self, value, encoder):
        return Jsonb(value, dumps=get_json_dumps(encoder))

    def subtract_temporals(self, internal_type, lhs, rhs):
        if internal_type == "DateField":
            lhs_sql, lhs_params = lhs
            rhs_sql, rhs_params = rhs
            params = (*lhs_params, *rhs_params)
            return "(interval '1 day' * (%s - %s))" % (lhs_sql, rhs_sql), params
        return super().subtract_temporals(internal_type, lhs, rhs)

    def explain_query_prefix(self, format=None, **options):
        extra = {}
        if serialize := options.pop("serialize", None):
            if serialize.upper() in {"TEXT", "BINARY"}:
                extra["SERIALIZE"] = serialize.upper()
        # Normalize options.
        if options:
            options = {
                name.upper(): "true" if value else "false"
                for name, value in options.items()
            }
            for valid_option in self.explain_options:
                value = options.pop(valid_option, None)
                if value is not None:
                    extra[valid_option] = value
        prefix = super().explain_query_prefix(format, **options)
        if format:
            extra["FORMAT"] = format
        if extra:
            prefix += " (%s)" % ", ".join("%s %s" % i for i in extra.items())
        return prefix

    def on_conflict_suffix_sql(self, fields, on_conflict, update_fields, unique_fields):
        if on_conflict == OnConflict.IGNORE:
            return "ON CONFLICT DO NOTHING"
        if on_conflict == OnConflict.UPDATE:
            return "ON CONFLICT(%s) DO UPDATE SET %s" % (
                ", ".join(map(self.quote_name, unique_fields)),
                ", ".join(
                    [
                        f"{field} = EXCLUDED.{field}"
                        for field in map(self.quote_name, update_fields)
                    ]
                ),
            )
        return super().on_conflict_suffix_sql(
            fields,
            on_conflict,
            update_fields,
            unique_fields,
        )

    def prepare_join_on_clause(self, lhs_table, lhs_field, rhs_table, rhs_field):
        lhs_expr, rhs_expr = super().prepare_join_on_clause(
            lhs_table, lhs_field, rhs_table, rhs_field
        )

        if lhs_field.db_type(self.connection) != rhs_field.db_type(self.connection):
            rhs_expr = Cast(rhs_expr, lhs_field)

        return lhs_expr, rhs_expr
