db.go

// Copyright (c) 2012-present The upper.io/db authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

// Package db provides a common interface to work with different data sources
// using adapters that wrap mature database drivers.
//
// The main purpose of db is to abstract common database operations and
// encourage users perform advanced operations directly using the underlying
// driver.  db supports the MySQL, PostgreSQL, SQLite and QL databases and
// provides partial support (CRUD, no transactions) for MongoDB.
//
//  go get upper.io/db.v2
//
// Usage
//
//  package main
//
//  import (
//  	"log"
//
//  	"upper.io/db.v2/postgresql" // Imports the postgresql adapter.
//  )
//
//  var settings = postgresql.ConnectionURL{
//  	Database: `booktown`,
//  	Host:     `demo.upper.io`,
//  	User:     `demouser`,
//  	Password: `demop4ss`,
//  }
//
//  // Book represents a book.
//  type Book struct {
//  	ID        uint   `db:"id"`
//  	Title     string `db:"title"`
//  	AuthorID  uint   `db:"author_id"`
//  	SubjectID uint   `db:"subject_id"`
//  }
//
//  func main() {
//  	sess, err := postgresql.Open(settings)
//  	if err != nil {
//  		log.Fatal(err)
//  	}
//  	defer sess.Close()
//
//  	var books []Book
//  	if err := sess.Collection("books").Find().OrderBy("title").All(&books); err != nil {
//  		log.Fatal(err)
//  	}
//
//  	log.Println("Books:")
//  	for _, book := range books {
//  		log.Printf("%q (ID: %d)\n", book.Title, book.ID)
//  	}
//  }
//
// See more usage examples and documentation for users at
// http://beta.upper.io/db.v2.
package db // import "upper.io/db.v2"

import (
	"fmt"
	"reflect"
)

// Constraint interface represents a condition.
type Constraint interface {
	Key() interface{}
	Value() interface{}
}

// Constraints interface represents an array of constraints.
type Constraints interface {
	Constraints() []Constraint
}

// Compound represents an statement that has one or many sentences joined by a
// compound operator, like AND or OR.
type Compound interface {
	Sentences() []Compound
	Operator() CompoundOperator
}

// CompoundOperator represents the operation on a compound statement.
type CompoundOperator uint

// Compound operators.
const (
	OperatorNone = CompoundOperator(iota)
	OperatorAnd
	OperatorOr
)

// RawValue interface represents values that can bypass SQL filters. Use with
// care.
type RawValue interface {
	fmt.Stringer
	Raw() string
}

// Function interface defines methods for representing database functions.
type Function interface {
	Arguments() []interface{}
	Name() string
}

// Marshaler is the interface implemented by struct fields that can marshal
// themselves into a value that can be saved to a database.
type Marshaler interface {
	MarshalDB() (interface{}, error)
}

// Unmarshaler is the interface implemented by struct fields that can unmarshal
// themselves from database data into a Go value.
type Unmarshaler interface {
	UnmarshalDB(interface{}) error
}

// Cond is a map that defines conditions for a query.
//
// Each entry of the map represents a condition (a column-value relation bound
// by a comparison operator). The comparison operator is optional and can be
// specified after the column name, if no comparison operator is provided the
// equality is used.
//
// Examples:
//
//  // Where age equals 18.
//  db.Cond{"age": 18}
//  //	// Where age is greater than or equal to 18.
//  db.Cond{"age >=": 18}
//
//  // Where id is in a list of ids.
//  db.Cond{"id IN": []{1, 2, 3}}
//
//  // Where age is lower than 18 (mongodb-like operator).
//  db.Cond{"age $lt": 18}
//
//  // Where age > 32 and age < 35
//  db.Cond{"age >": 32, "age <": 35}
type Cond map[interface{}]interface{}

// Constraints returns each one of the Cond map records as a constraint.
func (c Cond) Constraints() []Constraint {
	z := make([]Constraint, 0, len(c))
	for k, v := range c {
		z = append(z, NewConstraint(k, v))
	}
	return z
}

// Sentences return each one of the map records as a compound.
func (c Cond) Sentences() []Compound {
	z := make([]Compound, 0, len(c))
	for k, v := range c {
		z = append(z, Cond{k: v})
	}
	return z
}

// Operator returns the default compound operator.
func (c Cond) Operator() CompoundOperator {
	return OperatorNone
}

type rawValue struct {
	v string
}

func (r rawValue) Raw() string {
	return r.v
}

func (r rawValue) String() string {
	return r.Raw()
}

type compound struct {
	conds []Compound
}

func newCompound(c ...Compound) *compound {
	return &compound{c}
}

func (c *compound) Sentences() []Compound {
	return c.conds
}

func (c *compound) Operator() CompoundOperator {
	return OperatorNone
}

func (c *compound) push(a ...Compound) *compound {
	c.conds = append(c.conds, a...)
	return c
}

// Union represents an OR compound.
type Union struct {
	*compound
}

// Or adds more terms to the compound.
func (o *Union) Or(conds ...Compound) *Union {
	o.compound.push(conds...)
	return o
}

// Operator returns the OR operator.
func (o *Union) Operator() CompoundOperator {
	return OperatorOr
}

// And adds more terms to the compound.
func (a *Intersection) And(conds ...Compound) *Intersection {
	a.compound.push(conds...)
	return a
}

// Intersection represents an AND compound.
type Intersection struct {
	*compound
}

// Operator returns the AND operator.
func (a *Intersection) Operator() CompoundOperator {
	return OperatorAnd
}

type constraint struct {
	k interface{}
	v interface{}
}

func (c constraint) Key() interface{} {
	return c.k
}

func (c constraint) Value() interface{} {
	return c.v
}

// NewConstraint creates a constraint.
func NewConstraint(key interface{}, value interface{}) Constraint {
	return constraint{k: key, v: value}
}

// Func represents a database function.
//
// Examples:
//
//	// MOD(29, 9)
//	db.Func("MOD", 29, 9)
//
//	// CONCAT("foo", "bar")
//	db.Func("CONCAT", "foo", "bar")
//
//	// NOW()
//	db.Func("NOW")
//
//	// RTRIM("Hello  ")
//	db.Func("RTRIM", "Hello  ")
func Func(name string, args ...interface{}) Function {
	if len(args) == 1 {
		if reflect.TypeOf(args[0]).Kind() == reflect.Slice {
			iargs := make([]interface{}, len(args))
			for i := range args {
				iargs[i] = args[i]
			}
			args = iargs
		}
	}
	return &dbFunc{name: name, args: args}
}

type dbFunc struct {
	name string
	args []interface{}
}

func (f *dbFunc) Arguments() []interface{} {
	return f.args
}

func (f *dbFunc) Name() string {
	return f.name
}

// And joins conditions under logical conjunction. Conditions can be
// represented by db.Cond{}, db.Or() or db.And().
//
// Examples:
//
//	// name = "Peter" AND last_name = "Parker"
//	db.And(
//		db.Cond{"name": "Peter"},
//		db.Cond{"last_name": "Parker "},
//	)
//
//	// (name = "Peter" OR name = "Mickey") AND last_name = "Mouse"
//	db.And(
//		db.Or(
//			db.Cond{"name": "Peter"},
//			db.Cond{"name": "Mickey"},
//		),
//		db.Cond{"last_name": "Mouse"},
//	)
func And(conds ...Compound) *Intersection {
	return &Intersection{compound: newCompound(conds...)}
}

// Or joins conditions under logical disjunction. Conditions can be represented
// by db.Cond{}, db.Or() or db.And().
//
// Example:
//
//	// year = 2012 OR year = 1987
//	db.Or(
//		db.Cond{"year": 2012},
//		db.Cond{"year": 1987},
//	)
func Or(conds ...Compound) *Union {
	return &Union{compound: newCompound(conds...)}
}

// Raw marks chunks of data as protected, so they pass directly to the query
// without any filtering. Use with care.
//
// Example:
//
//	// SOUNDEX('Hello')
//	Raw("SOUNDEX('Hello')")
func Raw(s string) RawValue {
	return rawValue{v: s}
}

// Database is an interface that defines methods that must be satisfied by
// all database adapters.
type Database interface {
	// Driver returns the underlying driver the wrapper uses.
	//
	// In order to actually use the driver, the `interface{}` value needs to be
	// casted into the appropriate type.
	//
	// Example:
	//  internalSQLDriver := sess.Driver().(*sql.DB)
	Driver() interface{}

	// Open attempts to establish a connection with a DBMS.
	Open(ConnectionURL) error

	// Clone duplicates the current database session. Returns an error if the
	// clone did not succeed.
	// Clone() (Database, error)

	// Ping returns an error if the database manager could be reached.
	Ping() error

	// Close closes the currently active connection to the database and clears
	// caches.
	Close() error

	// Collection returns a collection reference given a table name.
	Collection(string) Collection

	// Collections returns the names of all non-system tables on the database.
	Collections() ([]string, error)

	// Name returns the name of the active database.
	Name() string

	// ConnectionURL returns the data used to set up the adapter.
	ConnectionURL() ConnectionURL
}

// Tx is an interface that enhaces the Database interface with additional
// methods for transactional operations.
//
// Example:
//  sess, err = postgresql.Open(settings)
//  ...
//
//  tx, err = sess.NewTransaction()
//  ...
//
//  artist, err = tx.Collection("artist")
//  ...
//
//  id, err = artist.Insert(item)
//  ...
//
//  err = tx.Commit()
type Tx interface {
	Database

	// Rollback discards all the instructions on the current transaction.
	Rollback() error

	// Commit commits the current transaction.
	Commit() error
}

// Collection is an interface that defines methods useful for handling tables.
type Collection interface {

	// Insert inserts a new item into the collection, it accepts a map or a
	// struct as argument and returns the ID of the newly added element. The type
	// of this ID depends on the database adapter. The ID returned by Insert()
	// can be passed directly to Find() to retrieve the recently added element.
	Insert(interface{}) (interface{}, error)

	// InsertReturning is like Insert() but it updates the passed pointer to map
	// or struct with the newly inserted element. This is all done atomically
	// within a transaction. If the database does not support transactions this
	// method returns db.ErrUnsupported.
	InsertReturning(interface{}) error

	// Exists returns true if the collection exists.
	Exists() bool

	// Find returns a result set with the given filters.
	Find(...interface{}) Result

	// Truncate removes all elements on the collection and resets the
	// collection's IDs.
	Truncate() error

	// Name returns the name of the collection.
	Name() string
}

// Result is an interface that defines methods useful for working with result
// sets.
type Result interface {
	// String satisfies fmt.Stringer and returns a SELECT statement for
	// the result.
	String() string

	// Limit defines the maximum number of results in this set. It only has
	// effect on `One()`, `All()` and `Next()`.
	Limit(int) Result

	// Offset ignores the first *n* results. It only has effect on `One()`, `All()`
	// and `Next()`.
	Offset(int) Result

	// OrderBy receives field names that define the order in which elements will be
	// returned in a query, field names may be prefixed with a minus sign (-)
	// indicating descending order, ascending order will be used otherwise.
	OrderBy(...interface{}) Result

	// Select defines specific columns to be returned from the elements of the
	// set.
	Select(...interface{}) Result

	// Where discards the initial filtering conditions and sets new ones.
	Where(...interface{}) Result

	// Group is used to group results that have the same value in the same column
	// or columns.
	Group(...interface{}) Result

	// Delete deletes all items within the result set. `Offset()` and `Limit()` are
	// not honoured by `Delete()`.
	Delete() error

	// Update modifies all items within the result set. `Offset()` and `Limit()`
	// are not honoured by `Update()`.
	Update(interface{}) error

	// Count returns the number of items that match the set conditions. `Offset()`
	// and `Limit()` are not honoured by `Count()`
	Count() (uint64, error)

	// Next fetches the next result within the result set and dumps it into the
	// given pointer to struct or pointer to map. You must call
	// `Close()` after finishing using `Next()`.
	Next(ptrToStruct interface{}) bool

	// Err returns the last error that has happened with the result set, nil
	// otherwise.
	Err() error

	// One fetches the first result within the result set and dumps it into the
	// given pointer to struct or pointer to map. The result set is automatically
	// closed after picking the element, so there is no need to call Close()
	// after using One().
	One(ptrToStruct interface{}) error

	// All fetches all results within the result set and dumps them into the
	// given pointer to slice of maps or structs.  The result set is
	// automatically closed, so there is no need to call Close() after
	// using All().
	All(sliceOfStructs interface{}) error

	// Close closes the result set.
	Close() error
}

// ConnectionURL represents a connection string
type ConnectionURL interface {
	// String returns the connection string that is going to be passed to the
	// adapter.
	String() string
}

// EnvEnableDebug can be used by adapters to determine if the user has enabled
// debugging.
//
// If the user sets the `UPPERIO_DB_DEBUG` environment variable to a
// non-empty value, all generated statements will be printed at runtime to
// the standard logger.
//
// Example:
//
//	UPPERIO_DB_DEBUG=1 go test
//
//	UPPERIO_DB_DEBUG=1 ./go-program
const EnvEnableDebug = `UPPERIO_DB_DEBUG`

var (
	_ = Function(&dbFunc{})
	_ = Constraints(Cond{})
	_ = Compound(Cond{})
	_ = Constraint(&constraint{})
	_ = RawValue(&rawValue{})
)