// Copyright 2024 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package pgcatalog

import (
	"io"

	"github.com/dolthub/go-mysql-server/sql"

	"github.com/dolthub/doltgresql/server/functions"
	"github.com/dolthub/doltgresql/server/tables"
	pgtypes "github.com/dolthub/doltgresql/server/types"
)

// PgTablesName is a constant to the pg_tables name.
const PgTablesName = "pg_tables"

// pgTableRow stores the data needed for a row in pg_tables: the table data and the schema it exists in.
type pgTableRow struct {
	Table       sql.Table
	TableSchema string
}

// InitPgTables handles registration of the pg_tables handler.
func InitPgTables() {
	tables.AddHandler(PgCatalogName, PgTablesName, PgTablesHandler{})
}

// PgTablesHandler is the handler for the pg_tables table.
type PgTablesHandler struct{}

var _ tables.Handler = PgTablesHandler{}

// Name implements the interface tables.Handler.
func (p PgTablesHandler) Name() string {
	return PgTablesName
}

// RowIter implements the interface tables.Handler.
func (p PgTablesHandler) RowIter(ctx *sql.Context, _ sql.Partition) (sql.RowIter, error) {
	// Use cached data from this process if it exists
	pgCatalogCache, err := getPgCatalogCache(ctx)
	if err != nil {
		return nil, err
	}

	if pgCatalogCache.tables == nil {
		var tables []pgTableRow
		// TODO: This should include information_schema tables
		// TODO: However, information schema is currently incorrect for Doltgres, so we exclude it.
		err := functions.IterateCurrentDatabase(ctx, functions.Callbacks{
			Table: func(ctx *sql.Context, schema functions.ItemSchema, table functions.ItemTable) (cont bool, err error) {
				if schema.Item.SchemaName() != sql.InformationSchemaDatabaseName {
					tables = append(tables, pgTableRow{table.Item, schema.Item.SchemaName()})
				}
				return true, nil
			},
		})
		if err != nil {
			return nil, err
		}

		pgCatalogCache.tables = tables
	}

	return &pgTablesRowIter{
		tables: pgCatalogCache.tables,
	}, nil
}

// PkSchema implements the interface tables.Handler.
func (p PgTablesHandler) PkSchema() sql.PrimaryKeySchema {
	return sql.PrimaryKeySchema{
		Schema:     pgTablesSchema,
		PkOrdinals: nil,
	}
}

// pgTablesSchema is the schema for pg_tables.
var pgTablesSchema = sql.Schema{
	{Name: "schemaname", Type: pgtypes.Name, Default: nil, Nullable: true, Source: PgTablesName},
	{Name: "tablename", Type: pgtypes.Name, Default: nil, Nullable: true, Source: PgTablesName},
	{Name: "tableowner", Type: pgtypes.Name, Default: nil, Nullable: true, Source: PgTablesName},
	{Name: "tablespace", Type: pgtypes.Name, Default: nil, Nullable: true, Source: PgTablesName},
	{Name: "hasindexes", Type: pgtypes.Bool, Default: nil, Nullable: true, Source: PgTablesName},
	{Name: "hasrules", Type: pgtypes.Bool, Default: nil, Nullable: true, Source: PgTablesName},
	{Name: "hastriggers", Type: pgtypes.Bool, Default: nil, Nullable: true, Source: PgTablesName},
	{Name: "rowsecurity", Type: pgtypes.Bool, Default: nil, Nullable: true, Source: PgTablesName},
}

// pgTablesRowIter is the sql.RowIter for the pg_tables table.
type pgTablesRowIter struct {
	// tables are the set of tables and the name of the schema they belong in
	tables []pgTableRow
	// idx is the current index in the iteration through the above slice
	idx int
}

var _ sql.RowIter = (*pgTablesRowIter)(nil)

// Next implements the interface sql.RowIter.
func (iter *pgTablesRowIter) Next(ctx *sql.Context) (sql.Row, error) {
	if iter.idx >= len(iter.tables) {
		return nil, io.EOF
	}
	defer func() {
		iter.idx++
	}()

	table := iter.tables[iter.idx].Table
	schema := iter.tables[iter.idx].TableSchema
	tableName := table.Name()

	var hasIndexes bool
	if it, ok := table.(sql.IndexAddressable); ok {
		idxs, err := it.GetIndexes(ctx)
		if err != nil {
			return nil, err
		}

		if len(idxs) > 0 {
			hasIndexes = true
		}
	}

	return sql.Row{
		schema,     // schemaname
		tableName,  // tablename
		"postgres", // tableowner
		nil,        // tablespace
		hasIndexes, // hasindexes
		false,      // hasrules  // TODO
		false,      // hastriggers // TODO
		false,      // rowsecurity
	}, nil
}

// Close implements the interface sql.RowIter.
func (iter *pgTablesRowIter) Close(ctx *sql.Context) error {
	return nil
}