package server

import (
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	_ "github.com/mattn/go-sqlite3" // SQLite driver
	"heckel.io/ntfy/util"
	"log"
	"strings"
	"time"
)

var (
	errUnexpectedMessageType = errors.New("unexpected message type")
)

// Messages cache
const (
	createMessagesTableQuery = `
		BEGIN;
		CREATE TABLE IF NOT EXISTS messages (
			id INTEGER PRIMARY KEY AUTOINCREMENT,
			mid TEXT NOT NULL,
			time INT NOT NULL,
			topic TEXT NOT NULL,
			message TEXT NOT NULL,
			title TEXT NOT NULL,
			priority INT NOT NULL,
			tags TEXT NOT NULL,
			click TEXT NOT NULL,
			actions TEXT NOT NULL,
			attachment_name TEXT NOT NULL,
			attachment_type TEXT NOT NULL,
			attachment_size INT NOT NULL,
			attachment_expires INT NOT NULL,
			attachment_url TEXT NOT NULL,
			sender TEXT NOT NULL,
			encoding TEXT NOT NULL,
			published INT NOT NULL
		);
		CREATE INDEX IF NOT EXISTS idx_mid ON messages (mid);
		CREATE INDEX IF NOT EXISTS idx_topic ON messages (topic);
		COMMIT;
	`
	insertMessageQuery = `
		INSERT INTO messages (mid, time, topic, message, title, priority, tags, click, actions, attachment_name, attachment_type, attachment_size, attachment_expires, attachment_url, sender, encoding, published) 
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
	`
	pruneMessagesQuery           = `DELETE FROM messages WHERE time < ? AND published = 1`
	selectRowIDFromMessageID     = `SELECT id FROM messages WHERE topic = ? AND mid = ?`
	selectMessagesSinceTimeQuery = `
		SELECT mid, time, topic, message, title, priority, tags, click, actions, attachment_name, attachment_type, attachment_size, attachment_expires, attachment_url, sender, encoding
		FROM messages 
		WHERE topic = ? AND time >= ? AND published = 1
		ORDER BY time, id
	`
	selectMessagesSinceTimeIncludeScheduledQuery = `
		SELECT mid, time, topic, message, title, priority, tags, click, actions, attachment_name, attachment_type, attachment_size, attachment_expires, attachment_url, sender, encoding
		FROM messages 
		WHERE topic = ? AND time >= ?
		ORDER BY time, id
	`
	selectMessagesSinceIDQuery = `
		SELECT mid, time, topic, message, title, priority, tags, click, actions, attachment_name, attachment_type, attachment_size, attachment_expires, attachment_url, sender, encoding
		FROM messages 
		WHERE topic = ? AND id > ? AND published = 1 
		ORDER BY time, id
	`
	selectMessagesSinceIDIncludeScheduledQuery = `
		SELECT mid, time, topic, message, title, priority, tags, click, actions, attachment_name, attachment_type, attachment_size, attachment_expires, attachment_url, sender, encoding
		FROM messages 
		WHERE topic = ? AND (id > ? OR published = 0)
		ORDER BY time, id
	`
	selectMessagesDueQuery = `
		SELECT mid, time, topic, message, title, priority, tags, click, actions, attachment_name, attachment_type, attachment_size, attachment_expires, attachment_url, sender, encoding
		FROM messages 
		WHERE time <= ? AND published = 0
		ORDER BY time, id
	`
	updateMessagePublishedQuery     = `UPDATE messages SET published = 1 WHERE mid = ?`
	selectMessagesCountQuery        = `SELECT COUNT(*) FROM messages`
	selectMessageCountForTopicQuery = `SELECT COUNT(*) FROM messages WHERE topic = ?`
	selectTopicsQuery               = `SELECT topic FROM messages GROUP BY topic`
	selectAttachmentsSizeQuery      = `SELECT IFNULL(SUM(attachment_size), 0) FROM messages WHERE sender = ? AND attachment_expires >= ?`
	selectAttachmentsExpiredQuery   = `SELECT mid FROM messages WHERE attachment_expires > 0 AND attachment_expires < ?`
)

// Schema management queries
const (
	currentSchemaVersion          = 7
	createSchemaVersionTableQuery = `
		CREATE TABLE IF NOT EXISTS schemaVersion (
			id INT PRIMARY KEY,
			version INT NOT NULL
		);
	`
	insertSchemaVersion      = `INSERT INTO schemaVersion VALUES (1, ?)`
	updateSchemaVersion      = `UPDATE schemaVersion SET version = ? WHERE id = 1`
	selectSchemaVersionQuery = `SELECT version FROM schemaVersion WHERE id = 1`

	// 0 -> 1
	migrate0To1AlterMessagesTableQuery = `
		BEGIN;
		ALTER TABLE messages ADD COLUMN title TEXT NOT NULL DEFAULT('');
		ALTER TABLE messages ADD COLUMN priority INT NOT NULL DEFAULT(0);
		ALTER TABLE messages ADD COLUMN tags TEXT NOT NULL DEFAULT('');
		COMMIT;
	`

	// 1 -> 2
	migrate1To2AlterMessagesTableQuery = `
		ALTER TABLE messages ADD COLUMN published INT NOT NULL DEFAULT(1);
	`

	// 2 -> 3
	migrate2To3AlterMessagesTableQuery = `
		BEGIN;
		ALTER TABLE messages ADD COLUMN click TEXT NOT NULL DEFAULT('');
		ALTER TABLE messages ADD COLUMN attachment_name TEXT NOT NULL DEFAULT('');
		ALTER TABLE messages ADD COLUMN attachment_type TEXT NOT NULL DEFAULT('');
		ALTER TABLE messages ADD COLUMN attachment_size INT NOT NULL DEFAULT('0');
		ALTER TABLE messages ADD COLUMN attachment_expires INT NOT NULL DEFAULT('0');
		ALTER TABLE messages ADD COLUMN attachment_owner TEXT NOT NULL DEFAULT('');
		ALTER TABLE messages ADD COLUMN attachment_url TEXT NOT NULL DEFAULT('');
		COMMIT;
	`
	// 3 -> 4
	migrate3To4AlterMessagesTableQuery = `
		ALTER TABLE messages ADD COLUMN encoding TEXT NOT NULL DEFAULT('');
	`

	// 4 -> 5
	migrate4To5AlterMessagesTableQuery = `
		BEGIN;
		CREATE TABLE IF NOT EXISTS messages_new (
			id INTEGER PRIMARY KEY AUTOINCREMENT,
			mid TEXT NOT NULL,
			time INT NOT NULL,
			topic TEXT NOT NULL,
			message TEXT NOT NULL,
			title TEXT NOT NULL,
			priority INT NOT NULL,
			tags TEXT NOT NULL,
			click TEXT NOT NULL,
			attachment_name TEXT NOT NULL,
			attachment_type TEXT NOT NULL,
			attachment_size INT NOT NULL,
			attachment_expires INT NOT NULL,
			attachment_url TEXT NOT NULL,
			attachment_owner TEXT NOT NULL,
			encoding TEXT NOT NULL,
			published INT NOT NULL
		);
		CREATE INDEX IF NOT EXISTS idx_mid ON messages_new (mid);
		CREATE INDEX IF NOT EXISTS idx_topic ON messages_new (topic);
		INSERT 
			INTO messages_new (
				mid, time, topic, message, title, priority, tags, click, attachment_name, attachment_type, 
				attachment_size, attachment_expires, attachment_url, attachment_owner, encoding, published)
			SELECT
				id, time, topic, message, title, priority, tags, click, attachment_name, attachment_type, 
				attachment_size, attachment_expires, attachment_url, attachment_owner, encoding, published
			FROM messages;
		DROP TABLE messages;
		ALTER TABLE messages_new RENAME TO messages;
		COMMIT;
	`

	// 5 -> 6
	migrate5To6AlterMessagesTableQuery = `
		ALTER TABLE messages ADD COLUMN actions TEXT NOT NULL DEFAULT('');
	`

	// 6 -> 7
	migrate6To7AlterMessagesTableQuery = `
		ALTER TABLE messages RENAME COLUMN attachment_owner TO sender;
	`
)

type messageCache struct {
	db  *sql.DB
	nop bool
}

// newSqliteCache creates a SQLite file-backed cache
func newSqliteCache(filename string, nop bool) (*messageCache, error) {
	db, err := sql.Open("sqlite3", filename)
	if err != nil {
		return nil, err
	}
	if err := setupCacheDB(db); err != nil {
		return nil, err
	}
	return &messageCache{
		db:  db,
		nop: nop,
	}, nil
}

// newMemCache creates an in-memory cache
func newMemCache() (*messageCache, error) {
	return newSqliteCache(createMemoryFilename(), false)
}

// newNopCache creates an in-memory cache that discards all messages;
// it is always empty and can be used if caching is entirely disabled
func newNopCache() (*messageCache, error) {
	return newSqliteCache(createMemoryFilename(), true)
}

// createMemoryFilename creates a unique memory filename to use for the SQLite backend.
// From mattn/go-sqlite3: "Each connection to ":memory:" opens a brand new in-memory
// sql database, so if the stdlib's sql engine happens to open another connection and
// you've only specified ":memory:", that connection will see a brand new database.
// A workaround is to use "file::memory:?cache=shared" (or "file:foobar?mode=memory&cache=shared").
// Every connection to this string will point to the same in-memory database."
func createMemoryFilename() string {
	return fmt.Sprintf("file:%s?mode=memory&cache=shared", util.RandomString(10))
}

func (c *messageCache) AddMessage(m *message) error {
	if m.Event != messageEvent {
		return errUnexpectedMessageType
	}
	if c.nop {
		return nil
	}
	published := m.Time <= time.Now().Unix()
	tags := strings.Join(m.Tags, ",")
	var attachmentName, attachmentType, attachmentURL string
	var attachmentSize, attachmentExpires int64
	if m.Attachment != nil {
		attachmentName = m.Attachment.Name
		attachmentType = m.Attachment.Type
		attachmentSize = m.Attachment.Size
		attachmentExpires = m.Attachment.Expires
		attachmentURL = m.Attachment.URL
	}
	var actionsStr string
	if len(m.Actions) > 0 {
		actionsBytes, err := json.Marshal(m.Actions)
		if err != nil {
			return err
		}
		actionsStr = string(actionsBytes)
	}
	_, err := c.db.Exec(
		insertMessageQuery,
		m.ID,
		m.Time,
		m.Topic,
		m.Message,
		m.Title,
		m.Priority,
		tags,
		m.Click,
		actionsStr,
		attachmentName,
		attachmentType,
		attachmentSize,
		attachmentExpires,
		attachmentURL,
		m.Sender,
		m.Encoding,
		published,
	)
	return err
}

func (c *messageCache) Messages(topic string, since sinceMarker, scheduled bool) ([]*message, error) {
	if since.IsNone() {
		return make([]*message, 0), nil
	} else if since.IsID() {
		return c.messagesSinceID(topic, since, scheduled)
	}
	return c.messagesSinceTime(topic, since, scheduled)
}

func (c *messageCache) messagesSinceTime(topic string, since sinceMarker, scheduled bool) ([]*message, error) {
	var rows *sql.Rows
	var err error
	if scheduled {
		rows, err = c.db.Query(selectMessagesSinceTimeIncludeScheduledQuery, topic, since.Time().Unix())
	} else {
		rows, err = c.db.Query(selectMessagesSinceTimeQuery, topic, since.Time().Unix())
	}
	if err != nil {
		return nil, err
	}
	return readMessages(rows)
}

func (c *messageCache) messagesSinceID(topic string, since sinceMarker, scheduled bool) ([]*message, error) {
	idrows, err := c.db.Query(selectRowIDFromMessageID, topic, since.ID())
	if err != nil {
		return nil, err
	}
	defer idrows.Close()
	if !idrows.Next() {
		return c.messagesSinceTime(topic, sinceAllMessages, scheduled)
	}
	var rowID int64
	if err := idrows.Scan(&rowID); err != nil {
		return nil, err
	}
	idrows.Close()
	var rows *sql.Rows
	if scheduled {
		rows, err = c.db.Query(selectMessagesSinceIDIncludeScheduledQuery, topic, rowID)
	} else {
		rows, err = c.db.Query(selectMessagesSinceIDQuery, topic, rowID)
	}
	if err != nil {
		return nil, err
	}
	return readMessages(rows)
}

func (c *messageCache) MessagesDue() ([]*message, error) {
	rows, err := c.db.Query(selectMessagesDueQuery, time.Now().Unix())
	if err != nil {
		return nil, err
	}
	return readMessages(rows)
}

func (c *messageCache) MarkPublished(m *message) error {
	_, err := c.db.Exec(updateMessagePublishedQuery, m.ID)
	return err
}

func (c *messageCache) MessageCount(topic string) (int, error) {
	rows, err := c.db.Query(selectMessageCountForTopicQuery, topic)
	if err != nil {
		return 0, err
	}
	defer rows.Close()
	var count int
	if !rows.Next() {
		return 0, errors.New("no rows found")
	}
	if err := rows.Scan(&count); err != nil {
		return 0, err
	} else if err := rows.Err(); err != nil {
		return 0, err
	}
	return count, nil
}

func (c *messageCache) Topics() (map[string]*topic, error) {
	rows, err := c.db.Query(selectTopicsQuery)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	topics := make(map[string]*topic)
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		topics[id] = newTopic(id)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return topics, nil
}

func (c *messageCache) Prune(olderThan time.Time) error {
	_, err := c.db.Exec(pruneMessagesQuery, olderThan.Unix())
	return err
}

func (c *messageCache) AttachmentBytesUsed(sender string) (int64, error) {
	rows, err := c.db.Query(selectAttachmentsSizeQuery, sender, time.Now().Unix())
	if err != nil {
		return 0, err
	}
	defer rows.Close()
	var size int64
	if !rows.Next() {
		return 0, errors.New("no rows found")
	}
	if err := rows.Scan(&size); err != nil {
		return 0, err
	} else if err := rows.Err(); err != nil {
		return 0, err
	}
	return size, nil
}

func (c *messageCache) AttachmentsExpired() ([]string, error) {
	rows, err := c.db.Query(selectAttachmentsExpiredQuery, time.Now().Unix())
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	ids := make([]string, 0)
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		ids = append(ids, id)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return ids, nil
}

func readMessages(rows *sql.Rows) ([]*message, error) {
	defer rows.Close()
	messages := make([]*message, 0)
	for rows.Next() {
		var timestamp, attachmentSize, attachmentExpires int64
		var priority int
		var id, topic, msg, title, tagsStr, click, actionsStr, attachmentName, attachmentType, attachmentURL, sender, encoding string
		err := rows.Scan(
			&id,
			&timestamp,
			&topic,
			&msg,
			&title,
			&priority,
			&tagsStr,
			&click,
			&actionsStr,
			&attachmentName,
			&attachmentType,
			&attachmentSize,
			&attachmentExpires,
			&attachmentURL,
			&sender,
			&encoding,
		)
		if err != nil {
			return nil, err
		}
		var tags []string
		if tagsStr != "" {
			tags = strings.Split(tagsStr, ",")
		}
		var actions []*action
		if actionsStr != "" {
			if err := json.Unmarshal([]byte(actionsStr), &actions); err != nil {
				return nil, err
			}
		}
		var att *attachment
		if attachmentName != "" && attachmentURL != "" {
			att = &attachment{
				Name:    attachmentName,
				Type:    attachmentType,
				Size:    attachmentSize,
				Expires: attachmentExpires,
				URL:     attachmentURL,
			}
		}
		messages = append(messages, &message{
			ID:         id,
			Time:       timestamp,
			Event:      messageEvent,
			Topic:      topic,
			Message:    msg,
			Title:      title,
			Priority:   priority,
			Tags:       tags,
			Click:      click,
			Actions:    actions,
			Attachment: att,
			Sender:     sender,
			Encoding:   encoding,
		})
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return messages, nil
}

func setupCacheDB(db *sql.DB) error {
	// If 'messages' table does not exist, this must be a new database
	rowsMC, err := db.Query(selectMessagesCountQuery)
	if err != nil {
		return setupNewCacheDB(db)
	}
	rowsMC.Close()

	// If 'messages' table exists, check 'schemaVersion' table
	schemaVersion := 0
	rowsSV, err := db.Query(selectSchemaVersionQuery)
	if err == nil {
		defer rowsSV.Close()
		if !rowsSV.Next() {
			return errors.New("cannot determine schema version: cache file may be corrupt")
		}
		if err := rowsSV.Scan(&schemaVersion); err != nil {
			return err
		}
		rowsSV.Close()
	}

	// Do migrations
	if schemaVersion == currentSchemaVersion {
		return nil
	} else if schemaVersion == 0 {
		return migrateFrom0(db)
	} else if schemaVersion == 1 {
		return migrateFrom1(db)
	} else if schemaVersion == 2 {
		return migrateFrom2(db)
	} else if schemaVersion == 3 {
		return migrateFrom3(db)
	} else if schemaVersion == 4 {
		return migrateFrom4(db)
	} else if schemaVersion == 5 {
		return migrateFrom5(db)
	} else if schemaVersion == 6 {
		return migrateFrom6(db)
	}
	return fmt.Errorf("unexpected schema version found: %d", schemaVersion)
}

func setupNewCacheDB(db *sql.DB) error {
	if _, err := db.Exec(createMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(createSchemaVersionTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(insertSchemaVersion, currentSchemaVersion); err != nil {
		return err
	}
	return nil
}

func migrateFrom0(db *sql.DB) error {
	log.Print("Migrating cache database schema: from 0 to 1")
	if _, err := db.Exec(migrate0To1AlterMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(createSchemaVersionTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(insertSchemaVersion, 1); err != nil {
		return err
	}
	return migrateFrom1(db)
}

func migrateFrom1(db *sql.DB) error {
	log.Print("Migrating cache database schema: from 1 to 2")
	if _, err := db.Exec(migrate1To2AlterMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(updateSchemaVersion, 2); err != nil {
		return err
	}
	return migrateFrom2(db)
}

func migrateFrom2(db *sql.DB) error {
	log.Print("Migrating cache database schema: from 2 to 3")
	if _, err := db.Exec(migrate2To3AlterMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(updateSchemaVersion, 3); err != nil {
		return err
	}
	return migrateFrom3(db)
}

func migrateFrom3(db *sql.DB) error {
	log.Print("Migrating cache database schema: from 3 to 4")
	if _, err := db.Exec(migrate3To4AlterMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(updateSchemaVersion, 4); err != nil {
		return err
	}
	return migrateFrom4(db)
}

func migrateFrom4(db *sql.DB) error {
	log.Print("Migrating cache database schema: from 4 to 5")
	if _, err := db.Exec(migrate4To5AlterMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(updateSchemaVersion, 5); err != nil {
		return err
	}
	return migrateFrom5(db)
}

func migrateFrom5(db *sql.DB) error {
	log.Print("Migrating cache database schema: from 5 to 6")
	if _, err := db.Exec(migrate5To6AlterMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(updateSchemaVersion, 6); err != nil {
		return err
	}
	return migrateFrom6(db)
}

func migrateFrom6(db *sql.DB) error {
	log.Print("Migrating cache database schema: from 6 to 7")
	if _, err := db.Exec(migrate6To7AlterMessagesTableQuery); err != nil {
		return err
	}
	if _, err := db.Exec(updateSchemaVersion, 7); err != nil {
		return err
	}
	return nil // Update this when a new version is added
}