package tools

import (
	"context"
	"fmt"
	"time"

	"nearle/models"
)

// "Compare online and counter sales."
//
// Two ledgers, not two columns of one. App orders live in `orders`; counter
// bills arrive from the tills and live in the POS tables. Nothing reconciles
// them, and the console's own Sales page says so in as many words — so this
// tool reports them side by side and states plainly that they are separate
// books. A single "total sales" figure invented by adding them would be the
// most useful-looking wrong number on the page.
//
// ── The model never sends a date ────────────────────────────────────────────
//
// It sends a number of days, and the range is computed here. Dates are the
// thing models get wrong most reliably — a format, a timezone, an off-by-one on
// "last week" — and every one of those errors produces a plausible figure for
// the wrong period, which is undetectable in a sentence.

// RevenueReader is the app-order side.
type RevenueReader interface {
	GetRevenueSummary(tid, lid int, fdate, tdate string) (*models.TenantRevenueSummary, error)
}

// CounterReader is the till side.
type CounterReader interface {
	SalesSummary(f models.PosSalesFilter) (*models.PosSalesSummary, error)
}

// ChannelTotals is one channel's takings over the period.
type ChannelTotals struct {
	Channel string  `json:"channel"`
	Revenue float64 `json:"revenue"`
	// Bills only exist on the counter side; app orders are counted by the
	// revenue read, which returns no order count. Omitted rather than reported
	// as 0, which would read as "no orders".
	Bills  int    `json:"bills,omitempty"`
	Ledger string `json:"ledger"`
	Caveat string `json:"caveat,omitempty"`
}

// defaultChannelDays is the period when nobody says otherwise.
//
// Seven, so the answer covers a full trading week including the weekend. A
// single day makes every Monday look like a collapse.
const defaultChannelDays = 7

// SalesByChannel builds the tool.
func SalesByChannel(orders RevenueReader, counter CounterReader, now func() time.Time) Tool {
	if now == nil {
		now = time.Now
	}

	return Tool{
		Name: "sales_by_channel",
		Description: "App order revenue and counter (till) takings side by side for one branch, over a recent period. " +
			"Use for questions comparing online and counter sales, or asking which channel is bigger. " +
			"The two come from separate ledgers and are never added together.",
		Needs: RequiresBranch,
		Scope: ScopeRead,
		Schema: Schema{Fields: []Field{{
			Name:        "days",
			Description: "How many days back to cover, ending today. Defaults to 7.",
			Kind:        KindInt,
			Min:         1,
			Max:         365,
			Default:     defaultChannelDays,
		}}},
		Handler: func(_ context.Context, req Request) (Result, error) {
			days := req.Int("days")
			if days <= 0 {
				days = defaultChannelDays
			}
			to := now()
			from := to.AddDate(0, 0, -(days - 1))
			fromDate, toDate := from.Format("2006-01-02"), to.Format("2006-01-02")

			rows := make([]ChannelTotals, 0, 2)

			revenue, err := orders.GetRevenueSummary(req.Caller.Tenantid, req.Caller.Locationid, fromDate, toDate)
			if err != nil {
				return Result{}, err
			}
			if revenue != nil {
				rows = append(rows, ChannelTotals{
					Channel: "App orders",
					Revenue: revenue.OverallRevenue,
					Ledger:  "orders",
				})
			}

			bills, err := counter.SalesSummary(models.PosSalesFilter{
				Locationid: req.Caller.Locationid,
				Fromdate:   fromDate,
				Todate:     toDate,
			})
			if err != nil {
				return Result{}, err
			}
			if bills != nil {
				rows = append(rows, ChannelTotals{
					Channel: "Counter",
					Revenue: bills.Grosssales,
					Bills:   bills.Billcount,
					Ledger:  "pos",
					// Gross, so it is not comparable like for like with the app
					// figure without saying so. Better stated on the row than
					// left for a reader to assume either way.
					Caveat: "Gross, before discount and round-off.",
				})
			}

			return Result{
				Rows:   rows,
				Count:  len(rows),
				Source: "/admin/sales",
				Scope:  "this branch",
				Note: fmt.Sprintf(
					"%s to %s. These are two separate ledgers — report them side by side and do not add them into one total.",
					fromDate, toDate),
			}, nil
		},
	}
}