package store

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"net/netip"

	"steward/internal/model"
)

const settingsKey = "settings"

// LoadState reads the whole configuration.
func (s *Store) LoadState(ctx context.Context) (*model.State, error) {
	st := &model.State{Settings: model.DefaultSettings(), Subnets: []*model.Subnet{}, Reservations: []*model.Reservation{}}
	if v, err := s.GetMeta(ctx, settingsKey); err != nil {
		return nil, err
	} else if v != "" {
		if err := json.Unmarshal([]byte(v), &st.Settings); err != nil {
			return nil, fmt.Errorf("reading settings: %w", err)
		}
	}
	if st.Settings.Options == nil {
		st.Settings.Options = []model.OptionValue{}
	}
	rows, err := s.db.QueryContext(ctx, `SELECT id, name, interface, prefix, pools, pool_order, address_order, lease_time, options, disabled, comment FROM subnets ORDER BY id`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	for rows.Next() {
		sn := &model.Subnet{}
		var prefix, pools, opts string
		var disabled int
		if err := rows.Scan(&sn.ID, &sn.Name, &sn.Interface, &prefix, &pools, &sn.PoolOrder, &sn.AddressOrder, &sn.LeaseTime, &opts, &disabled, &sn.Comment); err != nil {
			return nil, err
		}
		sn.Prefix, _ = netip.ParsePrefix(prefix)
		sn.Disabled = disabled != 0
		if err := json.Unmarshal([]byte(pools), &sn.Pools); err != nil {
			return nil, fmt.Errorf("subnet %d pools: %w", sn.ID, err)
		}
		if err := json.Unmarshal([]byte(opts), &sn.Options); err != nil {
			return nil, fmt.Errorf("subnet %d options: %w", sn.ID, err)
		}
		st.Subnets = append(st.Subnets, sn)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	rows, err = s.db.QueryContext(ctx, `SELECT id, mac, client_id, ip, hostname, options, lease_time, disabled, comment FROM reservations ORDER BY id`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	for rows.Next() {
		r := &model.Reservation{}
		var ip, opts string
		var disabled int
		if err := rows.Scan(&r.ID, &r.MAC, &r.ClientID, &ip, &r.Hostname, &opts, &r.LeaseTime, &disabled, &r.Comment); err != nil {
			return nil, err
		}
		r.IP, _ = netip.ParseAddr(ip)
		r.Disabled = disabled != 0
		if err := json.Unmarshal([]byte(opts), &r.Options); err != nil {
			return nil, fmt.Errorf("reservation %d options: %w", r.ID, err)
		}
		st.Reservations = append(st.Reservations, r)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	for _, sn := range st.Subnets {
		if sn.Pools == nil {
			sn.Pools = []model.Pool{}
		}
		if sn.Options == nil {
			sn.Options = []model.OptionValue{}
		}
	}
	for _, r := range st.Reservations {
		if r.Options == nil {
			r.Options = []model.OptionValue{}
		}
	}
	st.Sort()
	return st, nil
}

// SaveChanges writes configuration changes and their history entry in one
// transaction. The entry gets its ID and, when it undoes another, that
// entry is marked reverted.
func (s *Store) SaveChanges(ctx context.Context, changes []model.Change, e *model.HistoryEntry) error {
	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	for _, c := range changes {
		if err := applyChange(ctx, tx, c); err != nil {
			return fmt.Errorf("saving %s %d: %w", c.Kind, c.ID, err)
		}
	}
	if e != nil {
		var uid any
		if e.UserID != 0 {
			uid = e.UserID
		}
		var revertOf any
		if e.RevertOf != 0 {
			revertOf = e.RevertOf
		}
		res, err := tx.ExecContext(ctx, `INSERT INTO history (time, user_id, username, via, description, changes, revert_of) VALUES (?,?,?,?,?,?,?)`,
			ts(e.Time), uid, e.Username, e.Via, e.Description, jsonText(e.Changes), revertOf)
		if err != nil {
			return err
		}
		if e.ID, err = res.LastInsertId(); err != nil {
			return err
		}
		if e.RevertOf != 0 {
			if _, err := tx.ExecContext(ctx, `UPDATE history SET reverted_by = ? WHERE id = ?`, e.ID, e.RevertOf); err != nil {
				return err
			}
		}
	}
	return tx.Commit()
}

func applyChange(ctx context.Context, tx *sql.Tx, c model.Change) error {
	switch c.Kind {
	case model.KindSettings:
		if c.After == nil {
			return fmt.Errorf("settings can't be deleted")
		}
		_, err := tx.ExecContext(ctx, `INSERT INTO meta (key, value) VALUES (?, ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value`, settingsKey, string(c.After))
		return err
	case model.KindSubnet:
		if c.After == nil {
			_, err := tx.ExecContext(ctx, `DELETE FROM subnets WHERE id = ?`, c.ID)
			return err
		}
		var sn model.Subnet
		if err := json.Unmarshal(c.After, &sn); err != nil {
			return err
		}
		_, err := tx.ExecContext(ctx, `INSERT INTO subnets (id, name, interface, prefix, pools, pool_order, address_order, lease_time, options, disabled, comment) VALUES (?,?,?,?,?,?,?,?,?,?,?)
			ON CONFLICT(id) DO UPDATE SET name = excluded.name, interface = excluded.interface, prefix = excluded.prefix, pools = excluded.pools,
			pool_order = excluded.pool_order, address_order = excluded.address_order, lease_time = excluded.lease_time, options = excluded.options, disabled = excluded.disabled, comment = excluded.comment`,
			sn.ID, sn.Name, sn.Interface, sn.Prefix.String(), jsonText(nonNil(sn.Pools)), sn.PoolOrder, sn.AddressOrder, sn.LeaseTime, jsonText(nonNilOpts(sn.Options)), boolInt(sn.Disabled), sn.Comment)
		return err
	case model.KindReservation:
		if c.After == nil {
			_, err := tx.ExecContext(ctx, `DELETE FROM reservations WHERE id = ?`, c.ID)
			return err
		}
		var r model.Reservation
		if err := json.Unmarshal(c.After, &r); err != nil {
			return err
		}
		_, err := tx.ExecContext(ctx, `INSERT INTO reservations (id, mac, client_id, ip, hostname, options, lease_time, disabled, comment) VALUES (?,?,?,?,?,?,?,?,?)
			ON CONFLICT(id) DO UPDATE SET mac = excluded.mac, client_id = excluded.client_id, ip = excluded.ip, hostname = excluded.hostname,
			options = excluded.options, lease_time = excluded.lease_time, disabled = excluded.disabled, comment = excluded.comment`,
			r.ID, r.MAC, r.ClientID, r.IP.String(), r.Hostname, jsonText(nonNilOpts(r.Options)), r.LeaseTime, boolInt(r.Disabled), r.Comment)
		return err
	}
	return fmt.Errorf("unknown kind %q", c.Kind)
}

func nonNil(p []model.Pool) []model.Pool {
	if p == nil {
		return []model.Pool{}
	}
	return p
}

func nonNilOpts(o []model.OptionValue) []model.OptionValue {
	if o == nil {
		return []model.OptionValue{}
	}
	return o
}