package service

import (
	"context"
	"net/url"
	"strings"

	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
)

// Seed provenance and inventory (#50). A lot is one purchase — a specific packet
// of a specific variety, from a specific vendor, in a specific year — and it is
// owned by the buyer even when it points at a built-in plant. Lots are private:
// they are never shared along with a garden, because what you paid for seed is
// not part of a garden plan.

const (
	maxLotTextLen   = 200
	maxLotNotesLen  = 10_000
	maxSourceURLLen = 2000
	maxLotQuantity  = 1_000_000
	minPackedYear   = 1900
	maxPackedYear   = 2200
)

// lotUnits is the set of valid quantity units (mirrors the schema CHECK).
var lotUnits = map[string]struct{}{
	domain.UnitSeeds:   {},
	domain.UnitGrams:   {},
	domain.UnitOunces:  {},
	domain.UnitPackets: {},
	domain.UnitBulbs:   {},
	domain.UnitPlants:  {},
}

// SeedLotInput is the payload for recording a purchase.
type SeedLotInput struct {
	PlantID        int64
	Vendor         string
	SourceURL      string
	SKU            string
	LotCode        string
	PurchasedAt    *string
	PackedForYear  *int
	Quantity       float64
	Unit           string
	CostCents      *int
	GerminationPct *float64
	Notes          string
}

// SeedLotPatch is a partial update; nil fields are left unchanged. The nullable
// columns use a Set* flag to tell "clear to NULL" from "leave alone". PlantID is
// absent deliberately: re-pointing a purchase at a different variety would
// rewrite history rather than correct it.
type SeedLotPatch struct {
	Vendor            *string
	SourceURL         *string
	SKU               *string
	LotCode           *string
	SetPurchasedAt    bool
	PurchasedAt       *string
	SetPackedForYear  bool
	PackedForYear     *int
	Quantity          *float64
	Unit              *string
	SetCostCents      bool
	CostCents         *int
	SetGerminationPct bool
	GerminationPct    *float64
	Notes             *string
}

// ListSeedLots returns the actor's own lots, each with Used/Remaining filled in.
// Optionally narrowed to one plant.
func (s *Service) ListSeedLots(ctx context.Context, actorID int64, plantID *int64) ([]domain.SeedLot, error) {
	lots, err := s.store.ListSeedLotsForOwner(ctx, actorID, plantID)
	if err != nil {
		return nil, err
	}
	if err := s.fillRemaining(ctx, actorID, lots); err != nil {
		return nil, err
	}
	return lots, nil
}

// fillRemaining computes Used and Remaining for a slice of the actor's lots.
//
// Deliberately derived, never stored. The alternative — decrementing a column
// when you plant — drifts the moment anything edits or removes a planting behind
// its back, and once it has drifted there is no way to tell what the true number
// was. Attribution plus arithmetic can always be recomputed and audited.
func (s *Service) fillRemaining(ctx context.Context, actorID int64, lots []domain.SeedLot) error {
	if len(lots) == 0 {
		return nil
	}
	uses, err := s.store.SeedLotUsage(ctx, actorID)
	if err != nil {
		return err
	}
	used := make(map[int64]float64, len(lots))
	for _, u := range uses {
		n := derivedCount(u.RadiusCM, u.SpacingCM)
		if u.Count != nil {
			n = *u.Count
		}
		used[u.LotID] += float64(n)
	}
	for i := range lots {
		lots[i].Used = used[lots[i].ID]
		lots[i].Remaining = lots[i].Quantity - lots[i].Used
	}
	return nil
}

// ownSeedLot loads a lot and enforces that the actor owns it. Someone else's lot
// is ErrNotFound, not ErrForbidden — existence stays masked, same as gardens and
// other users' plants.
func (s *Service) ownSeedLot(ctx context.Context, actorID, lotID int64) (*domain.SeedLot, error) {
	l, err := s.store.GetSeedLot(ctx, lotID)
	if err != nil {
		return nil, err // ErrNotFound
	}
	if l.OwnerID != actorID {
		return nil, domain.ErrNotFound
	}
	return l, nil
}

// GetSeedLot returns one of the actor's own lots, with Used/Remaining filled in.
func (s *Service) GetSeedLot(ctx context.Context, actorID, lotID int64) (*domain.SeedLot, error) {
	l, err := s.ownSeedLot(ctx, actorID, lotID)
	if err != nil {
		return nil, err
	}
	one := []domain.SeedLot{*l}
	if err := s.fillRemaining(ctx, actorID, one); err != nil {
		return nil, err
	}
	return &one[0], nil
}

// CreateSeedLot records a purchase owned by the actor. The plant must be one the
// actor can see — a built-in or their own — since you can perfectly well buy
// generic Garlic from a vendor.
func (s *Service) CreateSeedLot(ctx context.Context, actorID int64, in SeedLotInput) (*domain.SeedLot, error) {
	if _, err := s.visiblePlant(ctx, actorID, in.PlantID); err != nil {
		return nil, err // ErrInvalidInput for an unknown or someone else's plant
	}
	l := &domain.SeedLot{
		OwnerID:        actorID,
		PlantID:        in.PlantID,
		Vendor:         strings.TrimSpace(in.Vendor),
		SourceURL:      strings.TrimSpace(in.SourceURL),
		SKU:            strings.TrimSpace(in.SKU),
		LotCode:        strings.TrimSpace(in.LotCode),
		PurchasedAt:    in.PurchasedAt,
		PackedForYear:  in.PackedForYear,
		Quantity:       in.Quantity,
		Unit:           in.Unit,
		CostCents:      in.CostCents,
		GerminationPct: in.GerminationPct,
		Notes:          strings.TrimSpace(in.Notes),
	}
	if err := finalizeSeedLot(l); err != nil {
		return nil, err
	}
	return s.store.CreateSeedLot(ctx, l)
}

// UpdateSeedLot applies a partial, version-guarded patch to the actor's own lot.
func (s *Service) UpdateSeedLot(ctx context.Context, actorID, lotID int64, patch SeedLotPatch, version int64) (*domain.SeedLot, error) {
	l, err := s.ownSeedLot(ctx, actorID, lotID)
	if err != nil {
		return nil, err
	}
	applySeedLotPatch(l, patch)
	if err := finalizeSeedLot(l); err != nil {
		return nil, err
	}
	l.Version = version
	updated, err := s.store.UpdateSeedLot(ctx, l)
	if err != nil {
		return updated, err
	}
	one := []domain.SeedLot{*updated}
	if ferr := s.fillRemaining(ctx, actorID, one); ferr != nil {
		return nil, ferr
	}
	return &one[0], nil
}

// DeleteSeedLot removes the actor's own lot. Plantings attributed to it survive
// with a null link (ON DELETE SET NULL) — the plants really were in the ground,
// whatever happened to the record of the packet.
func (s *Service) DeleteSeedLot(ctx context.Context, actorID, lotID int64) error {
	if _, err := s.ownSeedLot(ctx, actorID, lotID); err != nil {
		return err
	}
	return s.store.DeleteSeedLot(ctx, lotID)
}

// seedLotForPlanting validates a planting's lot attribution: the lot must be the
// actor's, and must be a lot OF the plant being planted. Attributing a garlic
// planting to a tomato lot is a data error that would silently corrupt every
// remaining count downstream, so it's refused rather than stored.
func (s *Service) seedLotForPlanting(ctx context.Context, actorID int64, lotID *int64, plantID int64) error {
	if lotID == nil {
		return nil
	}
	l, err := s.ownSeedLot(ctx, actorID, *lotID)
	if err != nil {
		return domain.ErrInvalidInput // unknown or not yours: an invalid reference
	}
	if l.PlantID != plantID {
		return domain.ErrInvalidInput
	}
	return nil
}

func applySeedLotPatch(l *domain.SeedLot, p SeedLotPatch) {
	if p.Vendor != nil {
		l.Vendor = strings.TrimSpace(*p.Vendor)
	}
	if p.SourceURL != nil {
		l.SourceURL = strings.TrimSpace(*p.SourceURL)
	}
	if p.SKU != nil {
		l.SKU = strings.TrimSpace(*p.SKU)
	}
	if p.LotCode != nil {
		l.LotCode = strings.TrimSpace(*p.LotCode)
	}
	if p.SetPurchasedAt {
		l.PurchasedAt = p.PurchasedAt
	}
	if p.SetPackedForYear {
		l.PackedForYear = p.PackedForYear
	}
	if p.Quantity != nil {
		l.Quantity = *p.Quantity
	}
	if p.Unit != nil {
		l.Unit = *p.Unit
	}
	if p.SetCostCents {
		l.CostCents = p.CostCents
	}
	if p.SetGerminationPct {
		l.GerminationPct = p.GerminationPct
	}
	if p.Notes != nil {
		l.Notes = strings.TrimSpace(*p.Notes)
	}
}

// finalizeSeedLot validates a built/merged lot. Shared by create and update.
func finalizeSeedLot(l *domain.SeedLot) error {
	if _, ok := lotUnits[l.Unit]; !ok {
		return domain.ErrInvalidInput
	}
	if !isFinite(l.Quantity) || l.Quantity < 0 || l.Quantity > maxLotQuantity {
		return domain.ErrInvalidInput
	}
	if len(l.Vendor) > maxLotTextLen || len(l.SKU) > maxLotTextLen || len(l.LotCode) > maxLotTextLen {
		return domain.ErrInvalidInput
	}
	if len(l.Notes) > maxLotNotesLen {
		return domain.ErrInvalidInput
	}
	if !validSourceURL(l.SourceURL) {
		return domain.ErrInvalidInput
	}
	if !validDatePtr(l.PurchasedAt) {
		return domain.ErrInvalidInput
	}
	if l.PackedForYear != nil && (*l.PackedForYear < minPackedYear || *l.PackedForYear > maxPackedYear) {
		return domain.ErrInvalidInput
	}
	if l.CostCents != nil && *l.CostCents < 0 {
		return domain.ErrInvalidInput
	}
	if l.GerminationPct != nil {
		g := *l.GerminationPct
		if !isFinite(g) || g < 0 || g > 100 {
			return domain.ErrInvalidInput
		}
	}
	return nil
}

// validSourceURL accepts an empty string or an absolute http(s) URL.
//
// This renders as a clickable link, so it is untrusted input in the way that
// matters: without the scheme check a "javascript:" URL stored here becomes
// script execution the moment someone clicks it. Only http and https, and only
// with a host — a relative or schemeless URL would resolve against pansy's own
// origin, which is never what a vendor link means.
func validSourceURL(raw string) bool {
	if raw == "" {
		return true
	}
	if len(raw) > maxSourceURLLen {
		return false
	}
	u, err := url.Parse(raw)
	if err != nil {
		return false
	}
	if u.Scheme != "http" && u.Scheme != "https" {
		return false
	}
	return u.Host != ""
}