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

// PgCastName is a constant to the pg_cast name.
const PgCastName = "pg_cast"

// InitPgCast handles registration of the pg_cast handler.
func InitPgCast() {
	tables.AddHandler(PgCatalogName, PgCastName, PgCastHandler{})
}

// PgCastHandler is the handler for the pg_cast table.
type PgCastHandler struct{}

var _ tables.Handler = PgCastHandler{}

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

// RowIter implements the interface tables.Handler.
func (p PgCastHandler) RowIter(ctx *sql.Context, partition sql.Partition) (sql.RowIter, error) {
	castsColl, err := core.GetCastsCollectionFromContext(ctx, "")
	if err != nil {
		return nil, err
	}
	var allCasts []casts.Cast
	err = castsColl.IterateCasts(ctx, func(c casts.Cast) (stop bool, err error) {
		allCasts = append(allCasts, c)
		return false, nil
	})
	if err != nil {
		return nil, err
	}
	return &pgCastRowIter{
		allCasts: allCasts,
		idx:      0,
	}, nil
}

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

// pgCastSchema is the schema for pg_cast.
var pgCastSchema = sql.Schema{
	{Name: "oid", Type: pgtypes.Oid, Default: nil, Nullable: false, Source: PgCastName},
	{Name: "castsource", Type: pgtypes.Oid, Default: nil, Nullable: false, Source: PgCastName},
	{Name: "casttarget", Type: pgtypes.Oid, Default: nil, Nullable: false, Source: PgCastName},
	{Name: "castfunc", Type: pgtypes.Oid, Default: nil, Nullable: false, Source: PgCastName},
	{Name: "castcontext", Type: pgtypes.InternalChar, Default: nil, Nullable: false, Source: PgCastName},
	{Name: "castmethod", Type: pgtypes.InternalChar, Default: nil, Nullable: false, Source: PgCastName},
}

// pgCastRowIter is the sql.RowIter for the pg_cast table.
type pgCastRowIter struct {
	allCasts []casts.Cast
	idx      int
}

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

// Next implements the interface sql.RowIter.
func (iter *pgCastRowIter) Next(ctx *sql.Context) (sql.Row, error) {
	if iter.idx >= len(iter.allCasts) {
		return nil, io.EOF
	}
	cast := iter.allCasts[iter.idx]
	iter.idx++
	var castContext string
	switch cast.CastType {
	case casts.CastType_Explicit:
		castContext = "e"
	case casts.CastType_Assignment:
		castContext = "a"
	case casts.CastType_Implicit:
		castContext = "i"
	}
	var castMethod string
	if cast.Function.IsValid() || cast.BuiltIn != nil {
		castMethod = "f"
	} else if cast.UseInOut {
		castMethod = "i"
	} else {
		castMethod = "b"
	}
	return sql.Row{
		cast.ID.AsId(),
		cast.ID.SourceType().AsId(),
		cast.ID.TargetType().AsId(),
		cast.Function.AsId(),
		castContext,
		castMethod,
	}, nil
}

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