from collections import namedtuple

from django.db.backends.base.introspection import BaseDatabaseIntrospection
from django.db.backends.base.introspection import FieldInfo as BaseFieldInfo
from django.db.backends.base.introspection import TableInfo
from django.db.models import Index

FieldInfo = namedtuple("FieldInfo", BaseFieldInfo._fields + ("is_autofield",))


class DatabaseIntrospection(BaseDatabaseIntrospection):
    # Maps type codes to Django Field types.
    data_types_reverse = {
        16: "BooleanField",
        17: "BinaryField",
        20: "BigIntegerField",
        21: "SmallIntegerField",
        23: "IntegerField",
        25: "TextField",
        700: "FloatField",
        701: "FloatField",
        869: "GenericIPAddressField",
        1042: "CharField",  # blank-padded
        1043: "CharField",
        1082: "DateField",
        1083: "TimeField",
        1114: "DateTimeField",
        1184: "DateTimeField",
        1186: "DurationField",
        1266: "TimeField",
        1700: "DecimalField",
        2950: "UUIDField",
        3802: "JSONField",
    }
    # A hook for subclasses.
    index_default_access_method = "btree"

    ignored_tables = []

    def get_field_type(self, data_type, description):
        field_type = super().get_field_type(data_type, description)
        if description.is_autofield or (
            # Required for pre-Django 4.1 serial columns.
            description.default
            and "nextval" in description.default
        ):
            if field_type == "IntegerField":
                return "AutoField"
            elif field_type == "BigIntegerField":
                return "BigAutoField"
            elif field_type == "SmallIntegerField":
                return "SmallAutoField"
        return field_type

    def get_table_list(self, cursor):
        """Return a list of table and view names in the current database."""
        cursor.execute(
            """
            SELECT
                c.relname,
                CASE
                    WHEN c.relispartition THEN 'p'
                    WHEN c.relkind IN ('m', 'v') THEN 'v'
                    ELSE 't'
                END
            FROM pg_catalog.pg_class c
            LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
            WHERE c.relkind IN ('f', 'm', 'p', 'r', 'v')
                AND n.nspname NOT IN ('pg_catalog', 'pg_toast')
                AND pg_catalog.pg_table_is_visible(c.oid)
        """
        )
        return [
            TableInfo(*row)
            for row in cursor.fetchall()
            if row[0] not in self.ignored_tables
        ]

    def get_table_description(self, cursor, table_name):
        """
        Return a description of the table with the DB-API cursor.description
        interface.
        """
        # Query the pg_catalog tables as cursor.description does not reliably
        # return the nullable property and information_schema.columns does not
        # contain details of materialized views.
        cursor.execute(
            """
            SELECT
                a.attname AS column_name,
                NOT (a.attnotnull OR (t.typtype = 'd' AND t.typnotnull)) AS is_nullable,
                pg_get_expr(ad.adbin, ad.adrelid) AS column_default,
                CASE WHEN collname = 'default' THEN NULL ELSE collname END AS collation,
                a.attidentity != '' AS is_autofield
            FROM pg_attribute a
            LEFT JOIN pg_attrdef ad ON a.attrelid = ad.adrelid AND a.attnum = ad.adnum
            LEFT JOIN pg_collation co ON a.attcollation = co.oid
            JOIN pg_type t ON a.atttypid = t.oid
            JOIN pg_class c ON a.attrelid = c.oid
            JOIN pg_namespace n ON c.relnamespace = n.oid
            WHERE c.relkind IN ('f', 'm', 'p', 'r', 'v')
                AND c.relname = %s
                AND n.nspname NOT IN ('pg_catalog', 'pg_toast')
                AND pg_catalog.pg_table_is_visible(c.oid)
        """,
            [table_name],
        )
        field_map = {line[0]: line[1:] for line in cursor.fetchall()}
        cursor.execute(
            "SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name)
        )
        return [
            FieldInfo(
                line.name,
                line.type_code,
                line.display_size,
                line.internal_size,
                line.precision,
                line.scale,
                *field_map[line.name],
            )
            for line in cursor.description
        ]

    def get_sequences(self, cursor, table_name, table_fields=()):
        cursor.execute(
            """
            SELECT
                s.relname AS sequence_name,
                a.attname AS colname
            FROM
                pg_class s
                JOIN pg_depend d ON d.objid = s.oid
                    AND d.classid = 'pg_class'::regclass
                    AND d.refclassid = 'pg_class'::regclass
                JOIN pg_attribute a ON d.refobjid = a.attrelid
                    AND d.refobjsubid = a.attnum
                JOIN pg_class tbl ON tbl.oid = d.refobjid
                    AND tbl.relname = %s
                    AND pg_catalog.pg_table_is_visible(tbl.oid)
            WHERE
                s.relkind = 'S';
        """,
            [table_name],
        )
        return [
            {"name": row[0], "table": table_name, "column": row[1]}
            for row in cursor.fetchall()
        ]

    def get_relations(self, cursor, table_name):
        """
        Return a dictionary of {field_name: (field_name_other_table, other_table)}
        representing all foreign keys in the given table.
        """
        cursor.execute(
            """
            SELECT a1.attname, c2.relname, a2.attname
            FROM pg_constraint con
            LEFT JOIN pg_class c1 ON con.conrelid = c1.oid
            LEFT JOIN pg_class c2 ON con.confrelid = c2.oid
            LEFT JOIN
                pg_attribute a1 ON c1.oid = a1.attrelid AND a1.attnum = con.conkey[1]
            LEFT JOIN
                pg_attribute a2 ON c2.oid = a2.attrelid AND a2.attnum = con.confkey[1]
            WHERE
                c1.relname = %s AND
                con.contype = 'f' AND
                c1.relnamespace = c2.relnamespace AND
                pg_catalog.pg_table_is_visible(c1.oid)
        """,
            [table_name],
        )
        return {row[0]: (row[2], row[1]) for row in cursor.fetchall()}

    def get_constraints(self, cursor, table_name):
        """
        Retrieve any constraints or keys (unique, pk, fk, check, index) across
        one or more columns. Also retrieve the definition of expression-based
        indexes.
        """
        constraints = {}
        # Loop over the key table, collecting things as constraints. The column
        # array must return column names in the same order in which they were
        # created.
        cursor.execute(
            """
            SELECT
                c.conname,
                array(
                    SELECT attname
                    FROM unnest(c.conkey) WITH ORDINALITY cols(colid, arridx)
                    JOIN pg_attribute AS ca ON cols.colid = ca.attnum
                    WHERE ca.attrelid = c.conrelid
                    ORDER BY cols.arridx
                ),
                c.contype,
                (SELECT fkc.relname || '.' || fka.attname
                FROM pg_attribute AS fka
                JOIN pg_class AS fkc ON fka.attrelid = fkc.oid
                WHERE fka.attrelid = c.confrelid AND fka.attnum = c.confkey[1]),
                cl.reloptions
            FROM pg_constraint AS c
            JOIN pg_class AS cl ON c.conrelid = cl.oid
            WHERE cl.relname = %s AND pg_catalog.pg_table_is_visible(cl.oid)
        """,
            [table_name],
        )
        for constraint, columns, kind, used_cols, options in cursor.fetchall():
            constraints[constraint] = {
                "columns": columns,
                "primary_key": kind == "p",
                "unique": kind in ["p", "u"],
                "foreign_key": tuple(used_cols.split(".", 1)) if kind == "f" else None,
                "check": kind == "c",
                "index": False,
                "definition": None,
                "options": options,
            }
        # Now get indexes
        cursor.execute(
            """
            SELECT
                indexname,
                array_agg(attname ORDER BY arridx),
                indisunique,
                indisprimary,
                array_agg(ordering ORDER BY arridx),
                amname,
                exprdef,
                s2.attoptions
            FROM (
                SELECT
                    c2.relname as indexname, idx.*, attr.attname, am.amname,
                    CASE
                        WHEN idx.indexprs IS NOT NULL THEN
                            pg_get_indexdef(idx.indexrelid)
                    END AS exprdef,
                    CASE am.amname
                        WHEN %s THEN
                            CASE (option & 1)
                                WHEN 1 THEN 'DESC' ELSE 'ASC'
                            END
                    END as ordering,
                    c2.reloptions as attoptions
                FROM (
                    SELECT *
                    FROM
                        pg_index i,
                        unnest(i.indkey, i.indoption)
                            WITH ORDINALITY koi(key, option, arridx)
                ) idx
                LEFT JOIN pg_class c ON idx.indrelid = c.oid
                LEFT JOIN pg_class c2 ON idx.indexrelid = c2.oid
                LEFT JOIN pg_am am ON c2.relam = am.oid
                LEFT JOIN
                    pg_attribute attr ON attr.attrelid = c.oid AND attr.attnum = idx.key
                WHERE c.relname = %s AND pg_catalog.pg_table_is_visible(c.oid)
            ) s2
            GROUP BY indexname, indisunique, indisprimary, amname, exprdef, attoptions;
        """,
            [self.index_default_access_method, table_name],
        )
        for (
            index,
            columns,
            unique,
            primary,
            orders,
            type_,
            definition,
            options,
        ) in cursor.fetchall():
            if index not in constraints:
                basic_index = (
                    type_ == self.index_default_access_method
                    and
                    # '_btree' references
                    # django.contrib.postgres.indexes.BTreeIndex.suffix.
                    not index.endswith("_btree")
                    and options is None
                )
                constraints[index] = {
                    "columns": columns if columns != [None] else [],
                    "orders": orders if orders != [None] else [],
                    "primary_key": primary,
                    "unique": unique,
                    "foreign_key": None,
                    "check": False,
                    "index": True,
                    "type": Index.suffix if basic_index else type_,
                    "definition": definition,
                    "options": options,
                }
        return constraints
