// Package runner orchestrates the once-a-day simulation against the store.
package runner

import (
	"context"
	"encoding/json"
	"fmt"
	"time"

	"wh/config"
	"wh/sim"
	"wh/store"
)

const (
	MetaConfig = "config"
	MetaDay    = "day"
	MetaMarket = "market"
)

// RunNextDay simulates the next day atomically: everything is committed
// together or not at all, so a crashed run can simply be repeated.
func RunNextDay(ctx context.Context, s *store.Store, cfg config.Config) (sim.DayResult, error) {
	var res sim.DayResult
	cfgJSON, err := json.Marshal(cfg)
	if err != nil {
		return res, err
	}
	err = s.WithTx(ctx, func(q *store.Q) error {
		if err := q.LockWorld(ctx); err != nil {
			return err
		}
		// Refuse to continue a world with different parameters.
		if prev, ok, err := q.GetMeta(ctx, MetaConfig); err != nil {
			return err
		} else if ok && prev != string(cfgJSON) {
			return fmt.Errorf("config differs from the one this world was created with:\n  stored:  %s\n  current: %s", prev, cfgJSON)
		}

		st, err := q.LoadState(ctx)
		if err != nil {
			return err
		}
		if st == nil {
			st = sim.NewState(cfg)
			if err := q.SetMeta(ctx, MetaConfig, string(cfgJSON)); err != nil {
				return err
			}
			if err := q.SaveState(ctx, st); err != nil { // day 0 snapshot
				return err
			}
		}

		var in sim.DayInput
		if in.Launches, err = q.PendingLaunches(ctx); err != nil {
			return err
		}
		if in.Uplinks, err = q.PendingUplinks(ctx); err != nil {
			return err
		}
		if res, err = st.RunDay(cfg, in); err != nil {
			return err
		}
		if err := q.SaveState(ctx, st); err != nil {
			return err
		}
		if err := q.RecordRun(ctx, res, time.Now().UTC().Format(time.RFC3339)); err != nil {
			return err
		}
		if err := q.AfterRun(ctx, st); err != nil {
			return err
		}
		mk, _ := json.Marshal(st.Market.Prices)
		if err := q.SetMeta(ctx, MetaMarket, string(mk)); err != nil {
			return err
		}
		return q.SetMeta(ctx, MetaDay, fmt.Sprint(st.Day))
	})
	return res, err
}