package mdb

import (
	"log"
	"net"
	"os"

	"git.crumpington.com/public/jldb/lib/errs"
	"git.crumpington.com/public/jldb/lib/wal"
	"git.crumpington.com/public/jldb/mdb/change"
	"git.crumpington.com/public/jldb/mdb/pfile"
)

func (db *Database) repSendState(conn net.Conn) error {
	pf, err := pfile.Open(pageFilePath(db.rootDir))
	if err != nil {
		return err
	}
	defer pf.Close()
	return pf.Send(conn, db.conf.NetTimeout)
}

func (db *Database) repRecvState(conn net.Conn) error {
	finalPath := pageFilePath(db.rootDir)
	tmpPath := finalPath + ".dl"
	if err := pfile.Recv(conn, tmpPath, db.conf.NetTimeout); err != nil {
		return err
	}

	if err := os.Rename(tmpPath, finalPath); err != nil {
		return errs.Unexpected.WithErr(err)
	}

	return nil
}

func (db *Database) repInitStorage() (err error) {
	db.pf, err = pfile.Open(pageFilePath(db.rootDir))
	return err
}

func (db *Database) repReplay(rec wal.Record) (err error) {
	db.changes, err = change.Read(db.changes[:0], rec.Reader)
	if err != nil {
		return err
	}

	return db.pf.ApplyChanges(db.changes)
}

func (db *Database) repLoadFromStorage() (err error) {
	db.idx, err = pfile.NewIndex(db.pf)
	if err != nil {
		return err
	}

	tx := db.snapshot.Load()
	err = pfile.IterateAllocated(db.pf, db.idx, func(cID, iID uint64, data []byte) error {
		return db.loadItem(tx, cID, iID, data)
	})
	if err != nil {
		return err
	}
	db.snapshot.Store(tx)
	return nil
}

func (db *Database) loadItem(tx *Snapshot, cID, iID uint64, data []byte) error {
	c, ok := db.collections[cID]
	if !ok {
		log.Printf("Failed to find collection %d for item in page file.", cID)
		return nil
	}

	return c.insertItem(tx, iID, data)
}

func (db *Database) repApply(rec wal.Record) (err error) {
	db.changes, err = change.Read(db.changes[:0], rec.Reader)
	if err != nil {
		return err
	}

	if err := db.pf.ApplyChanges(db.changes); err != nil {
		return err
	}

	if db.rep.Primary() {
		return nil
	}

	// For secondary, we need to also apply changes to memory.

	tx := db.snapshot.Load().begin()
	for _, change := range db.changes {
		if err = db.applyChange(tx, change); err != nil {
			return err
		}
	}
	tx.seqNum = rec.SeqNum
	tx.timestampMS = rec.TimestampMS
	tx.setReadOnly()
	db.snapshot.Store(tx)
	return nil
}

func (db *Database) applyChange(tx *Snapshot, change change.Change) error {
	c, ok := db.collections[change.CollectionID]
	if !ok {
		return nil
	}

	if change.Store {
		return c.upsertItem(tx, change.ItemID, change.Data)
	}

	// The only error this could return is NotFound. We'll ignore that error here.
	c.deleteItem(tx, change.ItemID)
	return nil
}