package store

import (
	"context"
	"errors"
	"time"

	"github.com/jackc/pgx/v5"

	"github.com/jackc/pgx/v5/pgconn"
	"github.com/szabadpalya/api/internal/store/dbgen"
)

// Admin shapes carry the raw column values, unlike the public ones: the editor
// has to round-trip DRAFT and ELUTASITVA, which never reach a visitor.

type AdminCampaignRow struct {
	ID          string `json:"id"`
	Slug        string `json:"slug"`
	Title       string `json:"title"`
	Status      string `json:"status"`
	GoalAmount  int    `json:"goalAmount"`
	Owner       string `json:"owner"`
	PledgeCount int    `json:"pledgeCount"`
}

// Owner is the person a campaign belongs to. Always a person — the table was
// called Organization until migration 0003.
type Owner struct {
	ID   string `json:"id"`
	Name string `json:"name"`
	// Carried so an owner editor can show and change the photo. Empty means the
	// organisation has none and its initials are used instead.
	AvatarURL string `json:"avatarUrl,omitempty"`
}

type AdminTier struct {
	ID                string   `json:"id"`
	Type              string   `json:"type"`
	Price             int      `json:"price"`
	ListPrice         *int     `json:"listPrice"`
	Title             string   `json:"title"`
	Includes          []string `json:"includes"`
	InventoryLimit    *int     `json:"inventoryLimit"`
	EstimatedDelivery string   `json:"estimatedDelivery"`
	Featured          bool     `json:"featured"`
	// PledgeCount is why a tier may refuse to be deleted, so the editor needs
	// it to explain itself before the user tries.
	PledgeCount int `json:"pledgeCount"`
}

type AdminCampaign struct {
	ID         string         `json:"id"`
	Slug       string         `json:"slug"`
	Title      string         `json:"title"`
	Category   string         `json:"category"`
	Summary    string         `json:"summary"`
	Art        string         `json:"art"`
	GoalAmount int            `json:"goalAmount"`
	EndsAt     string         `json:"endsAt"`
	Status     string         `json:"status"`
	OwnerID    string         `json:"ownerId"`
	Story      []StorySection `json:"story"`
	Tiers      []AdminTier    `json:"tiers"`
}

// ErrSlugTaken and ErrHasPledges are the two failures the editor has to
// explain in Hungarian rather than as a 500.
var (
	ErrSlugTaken  = errors.New("slug already taken")
	ErrHasPledges = errors.New("campaign has pledges")
)

func (s *Store) ListAdminCampaigns(ctx context.Context) ([]AdminCampaignRow, error) {
	rows, err := s.q.ListAdminCampaigns(ctx)
	if err != nil {
		return nil, err
	}
	out := make([]AdminCampaignRow, 0, len(rows))
	for _, r := range rows {
		out = append(out, AdminCampaignRow{
			ID:          r.ID,
			Slug:        r.Slug,
			Title:       r.Title,
			Status:      r.Status,
			GoalAmount:  r.GoalAmount,
			Owner:       r.Name,
			PledgeCount: r.PledgeCount,
		})
	}
	return out, nil
}

func (s *Store) ListOwners(ctx context.Context) ([]Owner, error) {
	rows, err := s.q.ListOwners(ctx)
	if err != nil {
		return nil, err
	}
	out := make([]Owner, 0, len(rows))
	for _, r := range rows {
		out = append(out, Owner{ID: r.ID, Name: r.Name, AvatarURL: r.AvatarUrl})
	}
	return out, nil
}

func (s *Store) GetAdminCampaign(ctx context.Context, slug string) (*AdminCampaign, error) {
	r, err := s.q.GetAdminCampaign(ctx, slug)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, err
	}

	c := &AdminCampaign{
		ID:         r.ID,
		Slug:       r.Slug,
		Title:      r.Title,
		Category:   r.Category,
		Summary:    r.Summary,
		Art:        r.Art,
		GoalAmount: r.GoalAmount,
		EndsAt:     s.Day(r.EndsAt),
		Status:     r.Status,
		OwnerID:    r.OwnerID,
	}

	if c.Story, err = s.storySections(ctx, c.ID); err != nil {
		return nil, err
	}

	tiers, err := s.q.ListAdminTiers(ctx, c.ID)
	if err != nil {
		return nil, err
	}
	c.Tiers = make([]AdminTier, 0, len(tiers))
	for _, t := range tiers {
		tier := AdminTier{
			ID:             t.ID,
			Type:           t.Type,
			Price:          t.Price,
			ListPrice:      t.ListPrice,
			Title:          t.Title,
			Includes:       t.Includes,
			InventoryLimit: t.InventoryLimit,
			Featured:       t.Featured,
			PledgeCount:    t.PledgeCount,
		}
		if t.EstimatedDelivery != nil {
			tier.EstimatedDelivery = s.Day(*t.EstimatedDelivery)
		}
		c.Tiers = append(c.Tiers, tier)
	}
	return c, nil
}

// TierInput is one row of the tier editor. A row with an ID updates that tier,
// a row without one creates it, and a tier missing from the slice entirely is
// deleted — unless pledges reference it.
type TierInput struct {
	ID                string   `json:"id"`
	Type              string   `json:"type"`
	Price             int      `json:"price"`
	ListPrice         *int     `json:"listPrice"`
	Title             string   `json:"title"`
	Includes          []string `json:"includes"`
	InventoryLimit    *int     `json:"inventoryLimit"`
	EstimatedDelivery string   `json:"estimatedDelivery"`
	Featured          bool     `json:"featured"`
}

type CampaignInput struct {
	ID         string         `json:"id"`
	Slug       string         `json:"slug"`
	Title      string         `json:"title"`
	Category   string         `json:"category"`
	Summary    string         `json:"summary"`
	Art        string         `json:"art"`
	GoalAmount int            `json:"goalAmount"`
	EndsAt     string         `json:"endsAt"`
	Status     string         `json:"status"`
	OwnerID    string         `json:"ownerId"`
	Story      []StorySection `json:"story"`
	Tiers      []TierInput    `json:"tiers"`
}

type SaveResult struct {
	Slug string `json:"slug"`
	// KeptInUseTier is true when a tier the caller wanted gone was retained
	// because pledges point at it. The save still succeeded.
	KeptInUseTier bool `json:"keptInUseTier"`
}

// SaveCampaign updates an existing campaign together with its story and tiers,
// in one transaction, so a half-saved campaign cannot be observed.
//
// It cannot create one. Campaigns are set up by hand, directly in the database,
// which is why an input without an id — or with one that matches no row — is
// ErrNotFound rather than an insert.
func (s *Store) SaveCampaign(ctx context.Context, in CampaignInput) (*SaveResult, error) {
	if in.ID == "" {
		return nil, ErrNotFound
	}

	endsAt, err := s.EndOfDay(in.EndsAt)
	if err != nil {
		return nil, err
	}

	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)

	// Same generated queries, bound to the transaction instead of the pool.
	q := s.q.WithTx(tx)

	campaignID := in.ID
	affected, err := q.UpdateCampaign(ctx, dbgen.UpdateCampaignParams{
		Slug:       in.Slug,
		Title:      in.Title,
		Category:   in.Category,
		Summary:    in.Summary,
		Art:        in.Art,
		GoalAmount: in.GoalAmount,
		EndsAt:     endsAt,
		Status:     in.Status,
		OwnerID:    in.OwnerID,
		ID:         campaignID,
	})
	if err != nil {
		if isUniqueViolation(err, "campaigns_slug_key") {
			return nil, ErrSlugTaken
		}
		return nil, err
	}
	// Without the insert branch an unknown id would otherwise update nothing and
	// then write story rows against a campaign that does not exist.
	if affected == 0 {
		return nil, ErrNotFound
	}

	// Story sections carry no foreign keys, so replacing them wholesale is safe.
	if err := q.DeleteStorySections(ctx, campaignID); err != nil {
		return nil, err
	}
	for i, sec := range in.Story {
		if err := q.InsertStorySection(ctx, dbgen.InsertStorySectionParams{
			ID:         NewID(),
			CampaignID: campaignID,
			Heading:    sec.Heading,
			Body:       sec.Body,
			Position:   i,
		}); err != nil {
			return nil, err
		}
	}

	result := &SaveResult{Slug: in.Slug}

	// Which existing tiers survive this save, and which have pledges.
	counts, err := q.ListTierPledgeCounts(ctx, campaignID)
	if err != nil {
		return nil, err
	}
	pledged := map[string]int{}
	order := make([]string, 0, len(counts))
	for _, c := range counts {
		pledged[c.ID] = c.PledgeCount
		order = append(order, c.ID)
	}

	kept := map[string]bool{}
	for _, t := range in.Tiers {
		if t.ID != "" {
			kept[t.ID] = true
		}
	}

	// Positions are unique per campaign, so park every existing row out of the
	// way before assigning final values — otherwise a reorder collides midway.
	for i, id := range order {
		if err := q.ParkTierPosition(ctx, dbgen.ParkTierPositionParams{
			Position: -1 - i,
			ID:       id,
		}); err != nil {
			return nil, err
		}
	}

	// A tier the caller dropped is deleted, unless pledges reference it: money
	// already promised against a reward outranks an edit to the reward list.
	final := append([]TierInput(nil), in.Tiers...)
	for _, id := range order {
		if kept[id] {
			continue
		}
		if pledged[id] > 0 {
			result.KeptInUseTier = true
			t, err := s.tierByID(ctx, q, id)
			if err != nil {
				return nil, err
			}
			final = append(final, *t)
			continue
		}
		if err := q.DeleteTier(ctx, id); err != nil {
			return nil, err
		}
	}

	for i, t := range final {
		var delivery *time.Time
		if t.EstimatedDelivery != "" {
			d, err := s.EndOfDay(t.EstimatedDelivery)
			if err != nil {
				return nil, err
			}
			delivery = &d
		}
		if t.Includes == nil {
			t.Includes = []string{}
		}
		if t.ID != "" {
			err = q.UpdateTier(ctx, dbgen.UpdateTierParams{
				Type:              t.Type,
				Price:             t.Price,
				ListPrice:         t.ListPrice,
				Title:             t.Title,
				Includes:          t.Includes,
				InventoryLimit:    t.InventoryLimit,
				EstimatedDelivery: delivery,
				Featured:          t.Featured,
				Position:          i,
				ID:                t.ID,
			})
		} else {
			err = q.InsertTier(ctx, dbgen.InsertTierParams{
				ID:                NewID(),
				CampaignID:        campaignID,
				Type:              t.Type,
				Price:             t.Price,
				ListPrice:         t.ListPrice,
				Title:             t.Title,
				Includes:          t.Includes,
				InventoryLimit:    t.InventoryLimit,
				EstimatedDelivery: delivery,
				Featured:          t.Featured,
				Position:          i,
			})
		}
		if err != nil {
			return nil, err
		}
	}

	return result, tx.Commit(ctx)
}

// tierByID reads a tier back through whichever Queries it is handed, so the
// caller decides whether that is the pool or an open transaction.
func (s *Store) tierByID(ctx context.Context, q *dbgen.Queries, id string) (*TierInput, error) {
	r, err := q.GetTier(ctx, id)
	if err != nil {
		return nil, err
	}
	t := &TierInput{
		ID:             r.ID,
		Type:           r.Type,
		Price:          r.Price,
		ListPrice:      r.ListPrice,
		Title:          r.Title,
		Includes:       r.Includes,
		InventoryLimit: r.InventoryLimit,
		Featured:       r.Featured,
	}
	if r.EstimatedDelivery != nil {
		t.EstimatedDelivery = s.Day(*r.EstimatedDelivery)
	}
	return t, nil
}

// DeleteCampaign refuses once any money has been promised: the pledge rows are
// the record of who gave what, and losing them to a mis-click is unacceptable.
func (s *Store) DeleteCampaign(ctx context.Context, id string) error {
	pledges, err := s.q.CountCampaignPledges(ctx, id)
	if err != nil {
		return err
	}
	if pledges > 0 {
		return ErrHasPledges
	}
	affected, err := s.q.DeleteCampaign(ctx, id)
	if err != nil {
		return err
	}
	if affected == 0 {
		return ErrNotFound
	}
	return nil
}

func (s *Store) CampaignSlugByID(ctx context.Context, id string) (string, error) {
	slug, err := s.q.CampaignSlugByID(ctx, id)
	if errors.Is(err, pgx.ErrNoRows) {
		return "", ErrNotFound
	}
	return slug, err
}

func isUniqueViolation(err error, constraint string) bool {
	var pgErr *pgconn.PgError
	return errors.As(err, &pgErr) && pgErr.Code == "23505" &&
		(constraint == "" || pgErr.ConstraintName == constraint)
}