// 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 node

import (
	"context"
	"fmt"
	"slices"

	"github.com/cockroachdb/errors"
	"github.com/dolthub/go-mysql-server/sql"
	"github.com/dolthub/go-mysql-server/sql/plan"
	vitess "github.com/dolthub/vitess/go/vt/sqlparser"

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

// CreateDomain handles the CREATE DOMAIN statement.
type CreateDomain struct {
	SchemaName           string
	Name                 string
	AsType               *pgtypes.DoltgresType
	Collation            string
	HasDefault           bool
	DefaultExpr          sql.Expression
	IsNotNull            bool
	CheckConstraintNames []string
	CheckConstraints     sql.CheckConstraints
	overrides            sql.EngineOverrides
}

var _ sql.ExecSourceRel = (*CreateDomain)(nil)
var _ sql.NodeOverriding = (*CreateDomain)(nil)
var _ vitess.Injectable = (*CreateDomain)(nil)

// Children implements the interface sql.ExecSourceRel.
func (c *CreateDomain) Children() []sql.Node {
	return nil
}

// IsReadOnly implements the interface sql.ExecSourceRel.
func (c *CreateDomain) IsReadOnly() bool {
	return false
}

// Resolved implements the interface sql.ExecSourceRel.
func (c *CreateDomain) Resolved() bool {
	return true
}

// RowIter implements the interface sql.ExecSourceRel.
func (c *CreateDomain) RowIter(ctx *sql.Context, r sql.Row) (sql.RowIter, error) {
	schema, err := core.GetSchemaName(ctx, nil, c.SchemaName)
	if err != nil {
		return nil, err
	}
	collection, err := core.GetTypesCollectionFromContext(ctx, "")
	if err != nil {
		return nil, err
	}

	internalID := id.NewType(schema, c.Name)
	arrayID := id.NewType(schema, "_"+c.Name)

	if collection.HasType(ctx, internalID) {
		return nil, pgtypes.ErrTypeAlreadyExists.New(c.Name)
	}

	var defExpr string
	if c.DefaultExpr != nil {
		defExpr = c.DefaultExpr.String()
	}

	checkDefs := make([]*sql.CheckDefinition, len(c.CheckConstraints))
	for i, check := range c.CheckConstraints {
		checkName := c.CheckConstraintNames[i]
		if checkName == "" {
			checkName = generateCheckNameForDomain(c.Name, c.CheckConstraintNames)
			// add this to the list of names to avoid duplicates later in the loop
			c.CheckConstraintNames[i] = checkName
			check.Name = checkName
		}
		checkDefs[i], err = plan.NewCheckDefinition(ctx, check, sql.GetSchemaFormatter(c.overrides))
		if err != nil {
			return nil, err
		}
	}

	newType := pgtypes.NewDomainType(ctx, c.AsType, defExpr, c.IsNotNull, checkDefs, arrayID, internalID)
	err = collection.CreateType(ctx, newType)
	if err != nil {
		return nil, err
	}

	// create array type of this type
	arrayType := pgtypes.CreateArrayTypeFromBaseType(newType)
	err = collection.CreateType(ctx, arrayType)
	if err != nil {
		return nil, err
	}
	newType.Array = arrayType

	return sql.RowsToRowIter(), nil
}

// generateCheckNameForDomain generates a unique check constraint name for a domain when one is not provided. The
// name must be unique for this type, but doesn't need to be unique across all constraint names in the database.
// Postgres generates names like `domainname_check`, and then uses `domainname_check1`, `domainname_check2`, etc.
// Our behavior varies slightly, in that if a user provides a name that collides with a generated name, we will use
// `domain_check` (no suffix) before moving on to `domain_check2` etc.
func generateCheckNameForDomain(domainName string, allNames []string) string {
	name := domainName + "_check"
	for i := 1; ; i++ {
		if !slices.Contains(allNames, name) {
			return name
		}
		name = fmt.Sprintf("%s_check%d", domainName, i)
	}
}

// Schema implements the interface sql.ExecSourceRel.
func (c *CreateDomain) Schema(ctx *sql.Context) sql.Schema {
	return nil
}

// String implements the interface sql.ExecSourceRel.
func (c *CreateDomain) String() string {
	return "CREATE DOMAIN"
}

// WithChildren implements the interface sql.ExecSourceRel.
func (c *CreateDomain) WithChildren(ctx *sql.Context, children ...sql.Node) (sql.Node, error) {
	return plan.NillaryWithChildren(c, children...)
}

// WithOverrides implements the interface sql.NodeOverriding.
func (c *CreateDomain) WithOverrides(overrides sql.EngineOverrides) sql.Node {
	c.overrides = overrides
	return c
}

// WithResolvedChildren implements the interface vitess.Injectable.
func (c *CreateDomain) WithResolvedChildren(ctx context.Context, children []any) (any, error) {
	checksStartAt := 0
	var defExpr sql.Expression
	if c.HasDefault {
		expr, ok := children[0].(sql.Expression)
		if !ok {
			return nil, errors.Errorf("invalid vitess child, expected sql.Expression for Default value but got %t", children[0])
		}
		defExpr = expr
		checksStartAt = 1
	}
	var checks sql.CheckConstraints
	for i, child := range children[checksStartAt:] {
		expr, ok := child.(sql.Expression)
		if !ok {
			return nil, errors.Errorf("invalid vitess child, expected sql.Expression for Check constraint value but got %t", children[0])
		}
		checks = append(checks, &sql.CheckConstraint{
			Name:     c.CheckConstraintNames[i],
			Expr:     expr,
			Enforced: true,
		})
	}
	if !c.AsType.IsResolvedType() {
		sqlCtx, ok := ctx.(*sql.Context)
		if !ok {
			return nil, errors.Errorf("%T requires a SQL context for type resolution", c)
		}
		typeColl, err := core.GetTypesCollectionFromContext(sqlCtx, "")
		if err != nil {
			return nil, err
		}
		resolvedType, err := typeColl.ResolveType(sqlCtx, c.AsType.ID)
		if err != nil {
			return nil, err
		}
		c.AsType = resolvedType
	}
	if !c.AsType.IsDefined {
		return nil, pgtypes.ErrTypeIsOnlyAShell.New(c.AsType.Name())
	}
	return &CreateDomain{
		SchemaName:           c.SchemaName,
		Name:                 c.Name,
		AsType:               c.AsType,
		Collation:            c.Collation,
		HasDefault:           c.HasDefault,
		DefaultExpr:          defExpr,
		IsNotNull:            c.IsNotNull,
		CheckConstraintNames: c.CheckConstraintNames,
		CheckConstraints:     checks,
	}, nil
}

// DomainColumn represents the column name `VALUE.
// It is a placeholder column reference later
// used for column defined as the domain type.
type DomainColumn struct {
	Typ *pgtypes.DoltgresType
}

var _ vitess.Injectable = (*DomainColumn)(nil)
var _ sql.Expression = (*DomainColumn)(nil)

// Resolved implements the interface sql.Expression.
func (d *DomainColumn) Resolved() bool {
	return true
}

// String implements the interface sql.Expression.
func (d *DomainColumn) String() string {
	return "VALUE"
}

// Type implements the interface sql.Expression.
func (d *DomainColumn) Type(ctx *sql.Context) sql.Type {
	if d.Typ.IsEmptyType() {
		return pgtypes.Unknown
	}
	return d.Typ
}

// IsNullable implements the interface sql.Expression.
func (d *DomainColumn) IsNullable(ctx *sql.Context) bool {
	return false
}

// Eval implements the interface sql.Expression.
func (d *DomainColumn) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
	panic("DomainColumn is a placeholder expression, but Eval() was called")
}

// Children implements the interface sql.Expression.
func (d *DomainColumn) Children() []sql.Expression {
	return nil
}

// WithChildren implements the interface sql.Expression.
func (d *DomainColumn) WithChildren(ctx *sql.Context, children ...sql.Expression) (sql.Expression, error) {
	if len(children) != 0 {
		return nil, sql.ErrInvalidChildrenNumber.New(d, len(children), 0)
	}
	return d, nil
}

// WithResolvedChildren implements the interface vitess.Injectable.
func (d *DomainColumn) WithResolvedChildren(ctx context.Context, children []any) (any, error) {
	if len(children) != 0 {
		return nil, errors.Errorf("invalid vitess child count, expected `0` but got `%d`", len(children))
	}
	return d, nil
}