package tools

import (
	"context"
	"fmt"
	"sort"
	"strings"
	"time"

	"nearle/models"
)

// "Which orders are stuck?" — the first tool, and a real one.
//
// A delivery that is still `pending` some time after it was handed out is a job
// nobody has picked up. The rider may not have seen it, may have no device, may
// have put the phone down. The console cannot tell which, and does not need to:
// the wait itself is the fact worth surfacing, and every one of these is a
// customer waiting without knowing why.
//
// ── Derived, never remembered ───────────────────────────────────────────────
//
// Nothing stores "this job went unaccepted". It is computed from `assigntime`
// and `orderstatus`, both of which every delivery read already returns, so the
// answer does not depend on anybody having been watching when it happened.
//
// ── Why the two thresholds ──────────────────────────────────────────────────
//
// Ten minutes is worth a look; twenty-five needs somebody now. A single
// threshold either cries wolf at three minutes — which trains people to ignore
// it, and an ignored flag is worse than none — or stays silent until the
// customer has already called.

const (
	// StuckLookMinutes is when a wait becomes worth a glance.
	StuckLookMinutes = 10
	// StuckNowMinutes is when it needs a person.
	StuckNowMinutes = 25
	// stuckMaxRows caps one answer. A model handed four hundred rows summarises
	// them into a sentence nobody can check; a dispatcher can act on ten.
	stuckMaxRows = 50
)

// DeliveryReader is the one thing this tool needs from the rest of the app.
//
// Narrowed to a single method so the tool can be tested without a database, and
// so it cannot quietly grow a second dependency. The real implementation is
// `services.DeliveriesService`.
type DeliveryReader interface {
	GetDeliveries(input models.DeliveryQuery) []models.Deliveryinfo
}

// StuckOrder is one row of the answer.
//
// Field names are what the model will read back to a person, so they say what
// they mean: `WaitingMinutes`, not `delta`.
type StuckOrder struct {
	Deliveryid     int    `json:"deliveryid"`
	Orderid        string `json:"orderid"`
	Rider          string `json:"rider,omitempty"`
	Branch         string `json:"branch,omitempty"`
	Customer       string `json:"customer,omitempty"`
	AssignedAt     string `json:"assigned_at"`
	WaitingMinutes int    `json:"waiting_minutes"`
	// "look" or "now" — which bucket the wait falls in. Returned rather than
	// left to the model to work out from the number, so the threshold is
	// decided in one place and cannot be re-invented in a sentence.
	Urgency string `json:"urgency"`
	Action  string `json:"action"`
}

// StuckOrders builds the tool.
//
// `now` is injected so the tests can ask what the board looked like at a fixed
// instant. Production passes `time.Now`.
func StuckOrders(deliveries DeliveryReader, now func() time.Time) Tool {
	if now == nil {
		now = time.Now
	}

	return Tool{
		Name: "stuck_orders",
		Description: "Deliveries a rider has been given but has not accepted yet, oldest first. " +
			"Use for questions about jobs that are stuck, not moving, unaccepted, or riders who have not started. " +
			"Returns the wait in minutes and what to do about each one.",
		Scope: ScopeRead,
		Schema: Schema{Fields: []Field{{
			Name:        "minutes_waiting",
			Description: "Only count jobs unaccepted for at least this many minutes. Defaults to 10.",
			Kind:        KindInt,
			Min:         1,
			Max:         720,
			Default:     StuckLookMinutes,
		}}},
		Handler: func(_ context.Context, req Request) (Result, error) {
			threshold := req.Int("minutes_waiting")
			if threshold <= 0 {
				threshold = StuckLookMinutes
			}

			rows := deliveries.GetDeliveries(models.DeliveryQuery{
				Tenantid: req.Caller.Tenantid,
				// The caller's own branch when they have one. A branch user asking
				// "what is stuck?" means their shop; an admin with no home branch
				// means all of them.
				Locationid: req.Caller.Locationid,
				Pagesize:   500,
				Pageno:     1,
			})

			at := now()
			stuck := make([]StuckOrder, 0, 8)

			for _, row := range rows {
				waited, ok := unacceptedFor(row, at)
				if !ok || waited < time.Duration(threshold)*time.Minute {
					continue
				}
				minutes := int(waited.Minutes())

				urgency, action := "look", "Check the rider has seen it."
				if minutes >= StuckNowMinutes {
					urgency, action = "now", "Call the rider, or give the job to somebody else."
				}

				stuck = append(stuck, StuckOrder{
					Deliveryid: row.Deliveryid,
					Orderid:    row.Orderid,
					// `ridername` is not reliably a name — on tenant 916 every
					// rider has delivery statuses in that column too, and for two
					// of five the status is the MORE common value. Excluded by
					// vocabulary rather than by a hand-written list.
					Rider:          riderName(row.Ridername),
					Branch:         row.Locationname,
					Customer:       row.Deliverycustomer,
					AssignedAt:     row.Assigntime,
					WaitingMinutes: minutes,
					Urgency:        urgency,
					Action:         action,
				})
			}

			// Worst first, then longest waiting. This is a worklist, not a log:
			// the row to deal with next belongs at the top.
			sort.SliceStable(stuck, func(i, j int) bool {
				if stuck[i].Urgency != stuck[j].Urgency {
					return stuck[i].Urgency == "now"
				}
				return stuck[i].WaitingMinutes > stuck[j].WaitingMinutes
			})

			result := Result{
				Count:  len(stuck),
				Source: "/admin/dispatch",
				Scope:  scopeWords(req.Caller),
			}
			if len(stuck) > stuckMaxRows {
				result.Truncated = true
				result.Note = fmt.Sprintf(
					"%d jobs are waiting; the %d longest are listed. Say so — do not describe this as the full list.",
					len(stuck), stuckMaxRows)
				stuck = stuck[:stuckMaxRows]
			}
			result.Rows = stuck
			return result, nil
		},
	}
}

// unacceptedFor is how long a job has sat with nobody accepting it.
//
// Only `pending` counts. A job the rider accepted, picked up or delivered is
// not stuck however old it is, and `rejected` or `skipped` is a different
// problem with a different answer — those are somebody's to reassign, not to
// chase.
//
// A stamp that will not parse returns false rather than 1970. Reading an
// unparseable `assigntime` as the epoch would report every such row as fifty
// years late, which is the kind of number that gets a whole screen ignored.
func unacceptedFor(row models.Deliveryinfo, now time.Time) (time.Duration, bool) {
	if strings.ToLower(strings.TrimSpace(row.Orderstatus)) != "pending" {
		return 0, false
	}
	assigned, ok := parseStamp(row.Assigntime)
	if !ok {
		return 0, false
	}
	waited := now.Sub(assigned)
	if waited < 0 {
		// A clock ahead of ours, not a job from the future.
		return 0, false
	}
	return waited, true
}

// parseStamp reads `assigntime` as the writer actually writes it.
//
// Local wall-clock with no zone — `2026-09-23 14:05:31` — which is what
// `stampNow` produces. Parsed in the server's own location rather than UTC,
// because reading local digits as UTC would put every job five and a half hours
// out in India and turn a fresh assignment into a four-hour wait.
func parseStamp(raw string) (time.Time, bool) {
	text := strings.TrimSpace(raw)
	if text == "" {
		return time.Time{}, false
	}
	for _, layout := range []string{
		"2006-01-02 15:04:05",
		"2006-01-02T15:04:05",
		time.RFC3339,
	} {
		if at, err := time.ParseInLocation(layout, text, time.Local); err == nil {
			return at, true
		}
	}
	return time.Time{}, false
}

// riderName keeps a name and drops a status wearing one.
//
// `deliveries.ridername` carries both. Measured on tenant 916: rider 897 has
// "Varun" 69 times and "delivered" 75, so neither "first non-empty" nor "most
// common" finds the name. The statuses are excluded by vocabulary, so a status
// added to the ladder is excluded the same day.
func riderName(raw string) string {
	name := strings.ToLower(strings.TrimSpace(raw))
	if name == "" {
		return ""
	}
	for _, status := range []string{
		"pending", "accepted", "arrived", "picked", "active",
		"skipped", "rejected", "delivered", "cancelled", "waiting",
	} {
		if name == status {
			return ""
		}
	}
	return strings.TrimSpace(raw)
}

// scopeWords says what the answer covers, in words a person would use.
func scopeWords(caller Caller) string {
	if caller.Locationid > 0 {
		return "this branch"
	}
	return "all branches"
}