package core

import (
	"fmt"
	"log"
	"time"

	_ "github.com/mattn/go-sqlite3"
)

func AddSource(db DB, name string) error {
	_, err := db.Exec(`
		insert into sources (name)
		values (?)
	`, name)

	return err
}

func GetSources(db DB) ([]string, error) {
	rows, err := db.Query(`
		select name
		from sources
	`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var names []string
	for rows.Next() {
		var name string
		if err = rows.Scan(&name); err != nil {
			return nil, err
		}
		names = append(names, name)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return names, nil
}

func SourceExists(db DB, source string) (bool, error) {
	row := db.QueryRow("select count(*) from sources where name = ?", source)
	var c int
	err := row.Scan(&c)
	return c > 0, err
}

func DeleteSource(db DB, name string) error {
	_, err := db.Exec(`
		delete from sources
		where name = ?
	`, name)

	return err
}

func GetState(db DB, source string) ([]byte, error) {
	row := db.QueryRow("select state from sources where name = ?", source)
	var state []byte
	err := row.Scan(&state)
	return state, err
}

func SetState(db DB, source string, state []byte) error {
	_, err := db.Exec("update sources set state = ? where name = ?", state, source)
	return err
}

// Given the results of a fetch, add new items, update existing items, and delete expired items.
//
// Returns the number of new and deleted items on success.
func UpdateWithFetchedItems(
	db DB,
	source string,
	state []byte,
	items []Item,
	now time.Time,
) (int, int, error) {
	var new int
	var del int
	var err error
	err = db.Transact(func(tx DB) error {
		new, del, err = updateWithFetchedItemsTx(tx, source, state, items, now)
		return err
	})
	return new, del, err
}

// Implementation logic for [UpdateWithFetchedItems], which executes this inside a transaction.
func updateWithFetchedItemsTx(
	db DB,
	source string,
	state []byte,
	items []Item,
	now time.Time,
) (int, int, error) {
	// Get the existing items
	existingItems, err := GetAllItemsForSource(db, source)
	if err != nil {
		return 0, 0, err
	}
	existingIds := map[string]bool{}
	existingItemsById := map[string]*Item{}
	for _, item := range existingItems {
		existingIds[item.Id] = true
		existingItemsById[item.Id] = &item
	}

	// Split the fetch into adds and updates
	var newItems []Item
	var updatedItems []Item
	for _, item := range items {
		if existingIds[item.Id] {
			updatedItems = append(updatedItems, item)
		} else {
			newItems = append(newItems, item)
		}
	}

	// Bulk insert the new items
	if err = AddItems(db, newItems); err != nil {
		return 0, 0, err
	}

	// Bulk update the existing items
	for _, item := range updatedItems {
		BackfillItem(&item, existingItemsById[item.Id])
	}
	if err = UpdateItems(db, updatedItems); err != nil {
		return 0, 0, err
	}

	envs, err := GetEnvs(db, source)
	if err != nil {
		return 0, 0, fmt.Errorf("failed to get envs for %s: %v", source, err)
	}

	// If the source has an on-create trigger, run it for each new item
	// On-create errors are ignored to avoid failing the fetch
	onCreateArgv, err := GetArgvForAction(db, source, "on_create")
	if err == nil && len(onCreateArgv) > 0 {
		var updatedNewItems []Item
		for _, item := range newItems {
			var updatedItem Item
			updatedItem, state, err = ExecuteItemAction(item, onCreateArgv, envs, state, time.Minute)
			if err != nil {
				log.Printf("error: on_create failed for %s/%s: %v", item.Source, item.Id, err)
			}
			updatedNewItems = append(updatedNewItems, updatedItem)
		}
		UpdateItems(db, updatedNewItems)
	}

	// Get the list of expired items
	fetchedIds := map[string]bool{}
	for _, item := range items {
		fetchedIds[item.Id] = true
	}
	expiredIds := map[string]bool{}
	for id := range existingIds {
		expiredIds[id] = !fetchedIds[id]
	}

	// Check expired items for deletion
	idsToDelete := map[string]bool{}
	for _, item := range existingItems {
		if expiredIds[item.Id] && item.Deletable(now) {
			idsToDelete[item.Id] = true
		}
	}

	// Delete each item to be deleted
	for id := range idsToDelete {
		if _, err = DeleteItem(db, source, id); err != nil {
			return 0, 0, err
		}
	}

	if err = SetState(db, source, state); err != nil {
		return 0, 0, err
	}

	return len(newItems), len(idsToDelete), nil
}