// Package bdb supplies the sql(b)oiler (d)ata(b)ase abstractions.
package bdb

import (
	"sort"

	"github.com/pkg/errors"
)

// Interface for a database driver. Functionality required to support a specific
// database type (eg, MySQL, Postgres etc.)
type Interface interface {
	TableNames(schema string, whitelist, blacklist []string) ([]string, error)
	Columns(schema, tableName string) ([]Column, error)
	PrimaryKeyInfo(schema, tableName string) (*PrimaryKey, error)
	ForeignKeyInfo(schema, tableName string) ([]ForeignKey, error)

	// TranslateColumnType takes a Database column type and returns a go column type.
	TranslateColumnType(Column) Column

	// UseLastInsertID should return true if the driver is capable of using
	// the sql.Exec result's LastInsertId
	UseLastInsertID() bool

	// UseTopClause should return true if the Database is capable of using
	// the SQL TOP clause
	UseTopClause() bool

	// Open the database connection
	Open() error
	// Close the database connection
	Close()

	// Dialect helpers, these provide the values that will go into
	// a queries.Dialect, so the query builder knows how to support
	// your database driver properly.
	LeftQuote() byte
	RightQuote() byte
	IndexPlaceholders() bool
}

// Tables returns the metadata for all tables, minus the tables
// specified in the blacklist.
func Tables(db Interface, schema string, whitelist, blacklist []string) ([]Table, error) {
	var err error

	names, err := db.TableNames(schema, whitelist, blacklist)
	if err != nil {
		return nil, errors.Wrap(err, "unable to get table names")
	}

	sort.Strings(names)

	var tables []Table
	for _, name := range names {
		t := Table{
			Name: name,
		}

		if t.Columns, err = db.Columns(schema, name); err != nil {
			return nil, errors.Wrapf(err, "unable to fetch table column info (%s)", name)
		}

		for i, c := range t.Columns {
			t.Columns[i] = db.TranslateColumnType(c)
		}

		if t.PKey, err = db.PrimaryKeyInfo(schema, name); err != nil {
			return nil, errors.Wrapf(err, "unable to fetch table pkey info (%s)", name)
		}

		if t.FKeys, err = db.ForeignKeyInfo(schema, name); err != nil {
			return nil, errors.Wrapf(err, "unable to fetch table fkey info (%s)", name)
		}

		setIsJoinTable(&t)

		tables = append(tables, t)
	}

	// Relationships have a dependency on foreign key nullability.
	for i := range tables {
		tbl := &tables[i]
		setForeignKeyConstraints(tbl, tables)
	}
	for i := range tables {
		tbl := &tables[i]
		setRelationships(tbl, tables)
	}

	return tables, nil
}

// setIsJoinTable if there are:
// A composite primary key involving two columns
// Both primary key columns are also foreign keys
func setIsJoinTable(t *Table) {
	if t.PKey == nil || len(t.PKey.Columns) != 2 || len(t.FKeys) < 2 || len(t.Columns) > 2 {
		return
	}

	for _, c := range t.PKey.Columns {
		found := false
		for _, f := range t.FKeys {
			if c == f.Column {
				found = true
				break
			}
		}
		if !found {
			return
		}
	}

	t.IsJoinTable = true
}

func setForeignKeyConstraints(t *Table, tables []Table) {
	for i, fkey := range t.FKeys {
		localColumn := t.GetColumn(fkey.Column)
		foreignTable := GetTable(tables, fkey.ForeignTable)
		foreignColumn := foreignTable.GetColumn(fkey.ForeignColumn)

		t.FKeys[i].Nullable = localColumn.Nullable
		t.FKeys[i].Unique = localColumn.Unique
		t.FKeys[i].ForeignColumnNullable = foreignColumn.Nullable
		t.FKeys[i].ForeignColumnUnique = foreignColumn.Unique
	}
}

func setRelationships(t *Table, tables []Table) {
	t.ToOneRelationships = toOneRelationships(*t, tables)
	t.ToManyRelationships = toManyRelationships(*t, tables)
}