package service

import (
	"context"
	"sort"
	"strings"

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

// Plant field bounds. Spacing is mature in-row spacing in cm; the ceiling is a
// generous sanity limit (also rejecting NaN/Inf). Name/notes are length-capped so
// untrusted input can't balloon storage; icon holds one emoji (possibly a
// multi-codepoint ZWJ sequence, hence a byte cap rather than length 1).
const (
	maxPlantNameLen   = 200
	maxPlantNotesLen  = 10_000
	maxPlantIconLen   = 32
	minPlantSpacingCM = 0.1
	maxPlantSpacingCM = 10_000 // 100 m — headroom for large trees/shrubs
	maxDaysToMaturity = 3650   // ~10 years
	maxPlantVendorLen = 200
)

// plantCategories is the set of valid category enum values (mirrors the schema
// CHECK constraint in 0001_init.sql).
var plantCategories = map[string]struct{}{
	domain.CategoryVegetable: {},
	domain.CategoryHerb:      {},
	domain.CategoryFlower:    {},
	domain.CategoryFruit:     {},
	domain.CategoryTreeShrub: {},
	domain.CategoryCover:     {},
}

// PlantInput is the mutable field set for creating a plant. DaysToMaturity is
// optional (nil = unknown).
type PlantInput struct {
	Name           string
	Category       string
	SpacingCM      float64
	Color          string
	Icon           string
	DaysToMaturity *int
	// Where this variety came from — the page you'd go back to to buy it again.
	// What you actually bought, and how much is left, is a SeedLot instead.
	SourceURL string
	Vendor    string
	Notes     string
}

// PlantPatch is a partial update: nil fields are left unchanged. DaysToMaturity
// is itself nullable, so SetDays distinguishes "clear to NULL" (SetDays=true,
// value nil) from "leave unchanged" (SetDays=false) — a plain nil can't.
type PlantPatch struct {
	Name           *string
	Category       *string
	SpacingCM      *float64
	Color          *string
	Icon           *string
	SetDays        bool
	DaysToMaturity *int
	SourceURL      *string
	Vendor         *string
	Notes          *string
}

// ListPlants returns the plants the actor can see: built-ins plus their own.
func (s *Service) ListPlants(ctx context.Context, actorID int64) ([]domain.Plant, error) {
	return s.store.ListPlantsForActor(ctx, actorID)
}

// PlantMatch is a candidate from FindPlants: the plant, plus what seed the actor
// has left of it, so an agent can say "you only have enough for half that bed"
// instead of confidently planting seed that doesn't exist.
type PlantMatch struct {
	domain.Plant
	// SeedRemaining is the total left across the actor's lots of this plant, and
	// SeedUnit the unit they're counted in — omitted when there are no lots, or
	// when lots disagree about the unit and summing them would be a lie.
	SeedRemaining *float64 `json:"seedRemaining,omitempty"`
	SeedUnit      string   `json:"seedUnit,omitempty"`
}

// maxPlantMatches caps FindPlants. A model given fifty candidates is not being
// helped; if the query is that broad the answer is to ask a better one.
const maxPlantMatches = 10

// FindPlants returns the plants in the actor's visible catalog (built-ins plus
// their own) whose name or category matches the query, best match first.
//
// It deliberately returns SEVERAL candidates rather than one guess. "garlic"
// against a catalog holding both "Garlic" and "German Red Garlic" is genuinely
// ambiguous, and a caller with the surrounding conversation is far better placed
// to disambiguate than a fuzzy-match heuristic here. An empty query returns the
// catalog head rather than nothing, so a caller can browse.
func (s *Service) FindPlants(ctx context.Context, actorID int64, query string) ([]PlantMatch, error) {
	plants, err := s.store.ListPlantsForActor(ctx, actorID)
	if err != nil {
		return nil, err
	}
	q := strings.ToLower(strings.TrimSpace(query))

	type scored struct {
		plant domain.Plant
		rank  int
	}
	ranked := make([]scored, 0, len(plants))
	for _, p := range plants {
		name := strings.ToLower(p.Name)
		switch {
		case q == "":
			ranked = append(ranked, scored{p, 3})
		case name == q:
			ranked = append(ranked, scored{p, 0})
		case strings.HasPrefix(name, q):
			ranked = append(ranked, scored{p, 1})
		case strings.Contains(name, q):
			ranked = append(ranked, scored{p, 2})
		case strings.Contains(strings.ToLower(p.Category), q):
			ranked = append(ranked, scored{p, 3})
		}
	}
	// Stable by rank then name, so the same query always answers the same way —
	// a tool whose results reshuffle between calls is one a model can't reason
	// about across turns.
	sort.SliceStable(ranked, func(i, j int) bool {
		if ranked[i].rank != ranked[j].rank {
			return ranked[i].rank < ranked[j].rank
		}
		return ranked[i].plant.Name < ranked[j].plant.Name
	})
	if len(ranked) > maxPlantMatches {
		ranked = ranked[:maxPlantMatches]
	}

	matches := make([]PlantMatch, 0, len(ranked))
	for _, r := range ranked {
		matches = append(matches, PlantMatch{Plant: r.plant})
	}
	if err := s.attachSeedRemaining(ctx, actorID, matches); err != nil {
		return nil, err
	}
	return matches, nil
}

// attachSeedRemaining fills SeedRemaining/SeedUnit from the actor's lots.
func (s *Service) attachSeedRemaining(ctx context.Context, actorID int64, matches []PlantMatch) error {
	if len(matches) == 0 {
		return nil
	}
	lots, err := s.ListSeedLots(ctx, actorID, nil)
	if err != nil {
		return err
	}
	byPlant := map[int64][]domain.SeedLot{}
	for _, l := range lots {
		byPlant[l.PlantID] = append(byPlant[l.PlantID], l)
	}
	for i := range matches {
		ls := byPlant[matches[i].ID]
		if len(ls) == 0 {
			continue
		}
		total := 0.0
		unit := ls[0].Unit
		for _, l := range ls {
			total += l.Remaining
			if l.Unit != unit {
				unit = "" // mixed units can't be summed honestly
			}
		}
		matches[i].SeedRemaining = &total
		matches[i].SeedUnit = unit
	}
	return nil
}

// CreatePlant adds a plant owned by the actor. To "clone" a built-in the client
// simply POSTs a copy — there is no dedicated endpoint, and the copy is owned by
// (and editable by) the actor.
func (s *Service) CreatePlant(ctx context.Context, actorID int64, in PlantInput) (*domain.Plant, error) {
	p := &domain.Plant{
		Name:           strings.TrimSpace(in.Name),
		Category:       in.Category,
		SpacingCM:      in.SpacingCM,
		Color:          in.Color,
		Icon:           strings.TrimSpace(in.Icon),
		DaysToMaturity: in.DaysToMaturity,
		SourceURL:      strings.TrimSpace(in.SourceURL),
		Vendor:         strings.TrimSpace(in.Vendor),
		Notes:          strings.TrimSpace(in.Notes),
	}
	if err := finalizePlant(p); err != nil {
		return nil, err
	}
	owner := actorID
	p.OwnerID = &owner
	return s.store.CreatePlant(ctx, p)
}

// writablePlant loads a plant and enforces that the actor may modify it. It is
// THE authorization point for plant mutation. Built-in rows (owner_id nil) are
// visible to everyone but read-only → ErrForbidden. A row owned by someone else
// is invisible → ErrNotFound (masking existence, as gardens/objects do). Only the
// actor's own rows are writable.
func (s *Service) writablePlant(ctx context.Context, actorID, plantID int64) (*domain.Plant, error) {
	p, err := s.store.GetPlant(ctx, plantID)
	if err != nil {
		return nil, err // ErrNotFound
	}
	if p.OwnerID == nil {
		return nil, domain.ErrForbidden // built-in: seeded and read-only
	}
	if *p.OwnerID != actorID {
		return nil, domain.ErrNotFound // another user's plant: not visible
	}
	return p, nil
}

// UpdatePlant applies a partial, version-guarded patch to the actor's own plant.
// On a version mismatch it returns (current, ErrVersionConflict).
func (s *Service) UpdatePlant(ctx context.Context, actorID, plantID int64, patch PlantPatch, version int64) (*domain.Plant, error) {
	p, err := s.writablePlant(ctx, actorID, plantID)
	if err != nil {
		return nil, err
	}
	applyPlantPatch(p, patch)
	if err := finalizePlant(p); err != nil {
		return nil, err
	}
	p.Version = version
	return s.store.UpdatePlant(ctx, p)
}

// DeletePlant removes the actor's own plant. A plant still referenced by any
// planting (even a removed one — the FK is RESTRICT) is refused with
// ErrPlantInUse rather than orphaning history; the client clones-and-edits or
// clears the plantings first.
//
// Seed lots are refused for a different reason: seed_lots.plant_id is ON DELETE
// CASCADE, so without this check deleting a plant would silently destroy the
// purchase records attached to it — vendor, cost, germination rate, all gone
// with no warning. Refusing lets the owner delete the lots deliberately if that
// is really what they meant.
func (s *Service) DeletePlant(ctx context.Context, actorID, plantID int64) error {
	if _, err := s.writablePlant(ctx, actorID, plantID); err != nil {
		return err
	}
	n, err := s.store.CountPlantingsForPlant(ctx, plantID)
	if err != nil {
		return err
	}
	if n > 0 {
		return domain.ErrPlantInUse
	}
	lots, err := s.store.CountSeedLotsForPlant(ctx, plantID)
	if err != nil {
		return err
	}
	if lots > 0 {
		return domain.ErrPlantInUse
	}
	return s.store.DeletePlant(ctx, plantID)
}

// applyPlantPatch mutates p with each provided (non-nil) patch field.
func applyPlantPatch(p *domain.Plant, patch PlantPatch) {
	if patch.Name != nil {
		p.Name = strings.TrimSpace(*patch.Name)
	}
	if patch.Category != nil {
		p.Category = *patch.Category
	}
	if patch.SpacingCM != nil {
		p.SpacingCM = *patch.SpacingCM
	}
	if patch.Color != nil {
		p.Color = *patch.Color
	}
	if patch.Icon != nil {
		p.Icon = strings.TrimSpace(*patch.Icon)
	}
	if patch.SetDays {
		p.DaysToMaturity = patch.DaysToMaturity
	}
	if patch.SourceURL != nil {
		p.SourceURL = strings.TrimSpace(*patch.SourceURL)
	}
	if patch.Vendor != nil {
		p.Vendor = strings.TrimSpace(*patch.Vendor)
	}
	if patch.Notes != nil {
		p.Notes = strings.TrimSpace(*patch.Notes)
	}
}

// finalizePlant validates a built/merged plant. Shared by create and update so
// both enforce the same invariants. isFinite/isHexColor live in objects.go.
func finalizePlant(p *domain.Plant) error {
	if p.Name == "" || len(p.Name) > maxPlantNameLen {
		return domain.ErrInvalidInput
	}
	if _, ok := plantCategories[p.Category]; !ok {
		return domain.ErrInvalidInput
	}
	if !isFinite(p.SpacingCM) || p.SpacingCM < minPlantSpacingCM || p.SpacingCM > maxPlantSpacingCM {
		return domain.ErrInvalidInput
	}
	if !isHexColor(p.Color) {
		return domain.ErrInvalidInput
	}
	if p.Icon == "" || len(p.Icon) > maxPlantIconLen {
		return domain.ErrInvalidInput
	}
	if p.DaysToMaturity != nil && (*p.DaysToMaturity < 1 || *p.DaysToMaturity > maxDaysToMaturity) {
		return domain.ErrInvalidInput
	}
	if len(p.Notes) > maxPlantNotesLen {
		return domain.ErrInvalidInput
	}
	if len(p.Vendor) > maxPlantVendorLen {
		return domain.ErrInvalidInput
	}
	// Rendered as a clickable link, so the scheme check is load-bearing (see
	// validSourceURL) rather than tidiness.
	if !validSourceURL(p.SourceURL) {
		return domain.ErrInvalidInput
	}
	return nil
}