package controllers

import (
	"math"

	"doormile/constants"
	"doormile/db"
	"doormile/internal/routing"
	"doormile/models"
	"doormile/utils"

	"github.com/gofiber/fiber/v2"
	"gorm.io/gorm"
)

// The shared batch-assign solver.
//
// This was the body of HubBatchAssign. It is lifted out so the admin console
// can run the same solver, because the console's agent layer needs it and the
// hub route is unreachable from an admin login.
//
// ─── Why the console could not use any existing route ──────────────────────
//
// The ops-layer skills raise findings that propose assigning a set of orders
// (SlaGuardianSkill's `assignMiler`), and that proposal has had no executor at
// all. The two candidate routes both failed, for different reasons:
//
//	POST /hub/bookings/batch-assign    sits behind HubStaffAuth, which refuses
//	                                   every token whose role is not 6. From the
//	                                   admin console it 403s on every click.
//	POST /admin/bookings/:id/assign-miler
//	                                   needs a CHOSEN rider per booking
//	                                   ({mileruserid}), and a finding does not
//	                                   pick one — it names orders, not riders.
//
// So the console needed the hub route's SOLVER (which picks riders itself) with
// the admin route's AUTH. Extracting the solver gives both routes one
// implementation; a second copy would be a third definition of "who gets this
// booking", after internal/assignment's AI path and AssignMilerToBooking.
//
// ─── What this is NOT ──────────────────────────────────────────────────────
//
// A greedy nearest-available-rider heuristic over haversine distance, capped
// per rider. Deliberately not internal/assignment's selectMilerWithAI (which
// reasons about hub load and on-time rate), and deliberately not a multi-stop
// VRP solver. It clears a queue; it does not optimise one. Stop ORDER comes
// afterwards from the Route Optimization API.

// batchRiderScope decides which riders are candidates and which bookings are in
// play. The hub and admin routes differ only here, which is the entire reason
// this split works.
type batchRiderScope struct {
	// Bookings narrows the pending-booking query. Hub: its own pincode prefix
	// and hub staff's tenant. Admin: the console login's tenant, if any.
	Bookings func(*gorm.DB) *gorm.DB
	// Riders narrows the rider query. Hub: riders on duty AT that hub. Admin:
	// riders on duty anywhere, because an admin batch is not hub-bound.
	Riders func(*gorm.DB) *gorm.DB
	// ActorID is recorded as the assigner on every BookingAssignment, so an
	// agent-proposed assignment is attributable to the operator who confirmed
	// it rather than appearing to come from nowhere.
	ActorID int
}

// BatchAssignResult is what both routes return.
type BatchAssignResult struct {
	Assigned        int          `json:"assigned"`
	Skipped         int          `json:"skipped"`
	Riderssequenced int          `json:"riderssequenced"`
	Results         []fiber.Map  `json:"results"`
}

// RunBatchAssign is the solver. bookingIDs empty means "everything the scope
// allows", which is how the hub route clears its whole queue; the console
// always passes an explicit set.
func RunBatchAssign(bookingIDs []int, capPerRider int, scope batchRiderScope) (BatchAssignResult, error) {
	if capPerRider <= 0 {
		capPerRider = defaultBatchAssignCapPerRider
	}

	bookingQuery := db.DB.Where("assignedmileruserid IS NULL AND status = ?", constants.BookingPendingPickup)
	if len(bookingIDs) > 0 {
		bookingQuery = bookingQuery.Where("bookingid IN ?", bookingIDs)
	}
	if scope.Bookings != nil {
		bookingQuery = scope.Bookings(bookingQuery)
	}

	var bookings []models.PickupBooking
	if err := bookingQuery.Order("createdat ASC").Find(&bookings).Error; err != nil {
		return BatchAssignResult{}, err
	}
	if len(bookings) == 0 {
		return BatchAssignResult{Results: []fiber.Map{}}, nil
	}

	// Every rider on duty, not only the idle ones. capPerRider is what limits a
	// round; requiring Available made that limit unreachable, because a rider
	// stopped being Available the moment they took the first booking of the
	// very batch being built.
	riderQuery := db.DB.Where("availabilitystatus IN ?", constants.MilerWorkingStatuses)
	if scope.Riders != nil {
		riderQuery = scope.Riders(riderQuery)
	}
	var riderProfiles []models.MilerProfile
	if err := riderQuery.Find(&riderProfiles).Error; err != nil {
		return BatchAssignResult{}, err
	}

	candidates := make([]*batchRiderCandidate, 0, len(riderProfiles))
	for _, mp := range riderProfiles {
		// Seed the count with what the rider is ALREADY holding. capPerRider
		// has to mean "stops in hand", not "stops added by this call" — now
		// that busy riders are eligible, counting only this call's additions
		// would hand five more to someone already carrying five.
		var openStops int64
		db.DB.Model(&models.BookingAssignment{}).
			Where("mileruserid = ? AND assignmentstatus IN ?", mp.Userid, []string{
				constants.AssignmentAssigned,
				constants.AssignmentAccepted,
			}).
			Count(&openStops)
		candidates = append(candidates, &batchRiderCandidate{
			userid: mp.Userid, lat: mp.Currentlatitude, lon: mp.Currentlongitude,
			assigned: int(openStops),
		})
	}

	results := make([]fiber.Map, 0, len(bookings))
	assignedCount, skippedCount := 0, 0

	for _, b := range bookings {
		var nearest *batchRiderCandidate
		nearestDist := math.MaxFloat64

		for _, cand := range candidates {
			if cand.assigned >= capPerRider {
				continue
			}
			d := haversineKM(b.Pickuplatitude, b.Pickuplongitude, cand.lat, cand.lon)
			if d < nearestDist {
				nearestDist = d
				nearest = cand
			}
		}

		if nearest == nil {
			results = append(results, fiber.Map{
				"bookingid": b.Bookingid, "bookingno": b.Bookingno,
				"assigned": false, "reason": "no available rider under capacity",
			})
			skippedCount++
			continue
		}

		actor := scope.ActorID
		if _, err := AssignMilerToBooking(b.Bookingid, nearest.userid, &actor); err != nil {
			results = append(results, fiber.Map{
				"bookingid": b.Bookingid, "bookingno": b.Bookingno,
				"assigned": false, "reason": err.Error(),
			})
			skippedCount++
			continue
		}

		nearest.assigned++
		results = append(results, fiber.Map{
			"bookingid": b.Bookingid, "bookingno": b.Bookingno,
			"assigned": true, "mileruserid": nearest.userid, "distance_km": nearestDist,
		})
		assignedCount++
	}

	// Batch assignment is exactly the case stop-ordering exists for: a rider
	// walks out of here with several bookings and otherwise no indication of
	// what order to run them in.
	//
	// Best-effort and deliberately after the assignments are committed: the
	// optimizer is a separate service over the network, and it failing must
	// leave the bookings assigned rather than undoing the batch.
	sequenced := 0
	for _, r := range ridersAssigned(results) {
		if _, err := routing.SequenceMilerStops(r); err != nil {
			utils.Warn("BatchAssign: stop sequencing failed",
				"miler_userid", r, "error", err)
			continue
		}
		sequenced++
	}

	return BatchAssignResult{
		Assigned:        assignedCount,
		Skipped:         skippedCount,
		Riderssequenced: sequenced,
		Results:         results,
	}, nil
}

// AdminBatchAssign — POST /api/v1/admin/bookings/batch-assign
//
// The admin counterpart of HubBatchAssign, and the executor behind the console
// ops layer's `assignMiler` proposal. Same solver, admin auth, and scoped to
// the console login's own tenant when there is one (a client login must not
// assign another client's parcels).
//
// Note on behaviour, because it differs from every other console write in the
// agent layer: this COMMITS. There is no preview/reconcile step — the same is
// true of the hub route it reuses. The console's proposal gate is therefore the
// only thing between a finding and a real assignment, which is why the UI must
// keep requiring an explicit click.
func AdminBatchAssign(c *fiber.Ctx) error {
	var req struct {
		Bookingids  []int `json:"bookingids"`
		MaxPerRider int   `json:"max_per_rider"`
	}
	if err := c.BodyParser(&req); err != nil {
		return utils.BadRequest(c, "invalid request body")
	}
	// Unlike the hub route, an empty set is refused here. The hub's empty case
	// means "clear this hub's queue", bounded by its pincode prefix; an admin
	// login has no such bound, so an empty body would mean "assign every
	// pending booking in the system" — never what a caller intended.
	if len(req.Bookingids) == 0 {
		return utils.BadRequest(c, "bookingids is required")
	}

	actorID, _ := c.Locals("userid").(int)

	// The route is registered behind middlewares.DoormileStaffOnly, so a
	// partner-tenant login never reaches this handler and `own` is always 0
	// today. The scoping below is therefore unreachable — kept deliberately,
	// as defence in depth: assignment is a Fleet Ops write and staff-only is
	// the current decision, but if that guard is ever relaxed the handler must
	// not silently start letting one client assign another's parcels. The same
	// belt-and-braces reasoning the ops-layer intents use for their domain
	// guards.
	own := consoleTenantID(c)

	result, err := RunBatchAssign(req.Bookingids, req.MaxPerRider, batchRiderScope{
		ActorID: actorID,
		Bookings: func(q *gorm.DB) *gorm.DB {
			if own == 0 {
				return q // Doormile staff
			}
			// A client login sees only its own bookings. A booking with no
			// tenant can't be proven to belong to them, so it stays invisible —
			// the same rule canAccessBooking applies to a single booking.
			return q.Where("tenantid = ?", own)
		},
		// Riders are not narrowed by tenant: riders are Doormile's, not a
		// client's, and a client login assigning its own parcels still draws
		// from the whole on-duty fleet.
		Riders: nil,
	})
	if err != nil {
		utils.Error("AdminBatchAssign: failed", "error", err)
		return utils.Internal(c, "failed to assign bookings")
	}

	return utils.OK(c, fiber.Map{
		"assigned":        result.Assigned,
		"skipped":         result.Skipped,
		"riderssequenced": result.Riderssequenced,
		"results":         result.Results,
	})
}