package repository

import (
	"context"
	_ "embed"
	"encoding/json"
	"fmt"
	"time"

	"github.com/prabhupadasays/spsays-bff/internal/model"
)

// rewardsSeedJSON is the catalog source of truth, kept in lockstep with the
// repo-root sadhna-rewards/rewards.json (the upload tool writes both). It is
// embedded so the BFF can seed/sync the catalog on startup with no external
// file dependency at runtime.
//
//go:embed sadhna_rewards.json
var rewardsSeedJSON []byte

// RewardRepo wraps Postgres access for the sādhana reward catalog and the
// per-user grants.
type RewardRepo struct{ pg *Postgres }

func NewRewardRepo(pg *Postgres) *RewardRepo { return &RewardRepo{pg: pg} }

type rewardsSeedFile struct {
	Rewards []struct {
		Key      string `json:"key"`
		Name     string `json:"name"`
		Meaning  string `json:"meaning"`
		ImageURL string `json:"image_url"`
		Active   bool   `json:"active"`
	} `json:"rewards"`
}

// Seed upserts the catalog from the embedded rewards.json by key, so editing
// a name/meaning or filling an image_url and redeploying keeps the DB in
// sync. Sort follows the file order. Idempotent.
func (r *RewardRepo) Seed(ctx context.Context) error {
	var f rewardsSeedFile
	if err := json.Unmarshal(rewardsSeedJSON, &f); err != nil {
		return fmt.Errorf("parse rewards seed: %w", err)
	}
	for i, rw := range f.Rewards {
		_, err := r.pg.Pool.Exec(ctx, `
			INSERT INTO sadhna_rewards (key, name, meaning, image_url, active, sort)
			VALUES ($1, $2, $3, $4, $5, $6)
			ON CONFLICT (key) DO UPDATE
			    SET name = EXCLUDED.name,
			        meaning = EXCLUDED.meaning,
			        image_url = EXCLUDED.image_url,
			        active = EXCLUDED.active,
			        sort = EXCLUDED.sort,
			        updated_at = now()`,
			rw.Key, rw.Name, rw.Meaning, rw.ImageURL, rw.Active, i,
		)
		if err != nil {
			return fmt.Errorf("seed reward %q: %w", rw.Key, err)
		}
	}
	return nil
}

// ListGiftable returns active rewards that have an image (so a celebration
// always has something to show), ordered by sort. This is the gifting pool.
func (r *RewardRepo) ListGiftable(ctx context.Context) ([]model.SadhnaReward, error) {
	rows, err := r.pg.Pool.Query(ctx, `
		SELECT id, key, name, meaning, image_url, active, sort
		FROM sadhna_rewards
		WHERE active = TRUE AND image_url <> ''
		ORDER BY sort`)
	if err != nil {
		return nil, fmt.Errorf("list giftable rewards: %w", err)
	}
	defer rows.Close()
	var out []model.SadhnaReward
	for rows.Next() {
		var rw model.SadhnaReward
		if err := rows.Scan(&rw.ID, &rw.Key, &rw.Name, &rw.Meaning, &rw.ImageURL, &rw.Active, &rw.Sort); err != nil {
			return nil, fmt.Errorf("scan reward: %w", err)
		}
		out = append(out, rw)
	}
	return out, rows.Err()
}

// GrantsByUser returns the user's earned rewards, newest first, with the
// reward embedded for direct rendering.
func (r *RewardRepo) GrantsByUser(ctx context.Context, userID string) ([]model.SadhnaRewardGrant, error) {
	rows, err := r.pg.Pool.Query(ctx, `
		SELECT g.milestone, g.granted_at,
		       w.id, w.key, w.name, w.meaning, w.image_url, w.active, w.sort
		FROM sadhna_reward_grants g
		JOIN sadhna_rewards w ON w.id = g.reward_id
		WHERE g.user_id = $1
		ORDER BY g.granted_at DESC, g.milestone DESC`,
		userID,
	)
	if err != nil {
		return nil, fmt.Errorf("grants by user: %w", err)
	}
	defer rows.Close()
	var out []model.SadhnaRewardGrant
	for rows.Next() {
		var g model.SadhnaRewardGrant
		if err := rows.Scan(
			&g.Milestone, &g.GrantedAt,
			&g.Reward.ID, &g.Reward.Key, &g.Reward.Name, &g.Reward.Meaning,
			&g.Reward.ImageURL, &g.Reward.Active, &g.Reward.Sort,
		); err != nil {
			return nil, fmt.Errorf("scan grant: %w", err)
		}
		out = append(out, g)
	}
	return out, rows.Err()
}

// GrantedRewardIDs returns the set of reward ids the user has already
// received, for avoiding repeats when picking the next gift.
func (r *RewardRepo) GrantedRewardIDs(ctx context.Context, userID string) (map[string]bool, error) {
	rows, err := r.pg.Pool.Query(ctx,
		`SELECT reward_id FROM sadhna_reward_grants WHERE user_id = $1`, userID)
	if err != nil {
		return nil, fmt.Errorf("granted reward ids: %w", err)
	}
	defer rows.Close()
	out := make(map[string]bool)
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, fmt.Errorf("scan reward id: %w", err)
		}
		out[id] = true
	}
	return out, rows.Err()
}

// LastGrantedRewardID returns the most recently granted reward id (or "" if
// none), used to avoid a back-to-back repeat once the pool has cycled.
func (r *RewardRepo) LastGrantedRewardID(ctx context.Context, userID string) (string, error) {
	var id string
	err := r.pg.Pool.QueryRow(ctx, `
		SELECT reward_id FROM sadhna_reward_grants
		WHERE user_id = $1 ORDER BY granted_at DESC, milestone DESC LIMIT 1`,
		userID,
	).Scan(&id)
	if err != nil {
		return "", nil // no rows → empty
	}
	return id, nil
}

// HasMilestone reports whether the user already has a grant for the given
// streak milestone (the idempotency guard).
func (r *RewardRepo) HasMilestone(ctx context.Context, userID string, milestone int) (bool, error) {
	var n int
	err := r.pg.Pool.QueryRow(ctx,
		`SELECT count(*) FROM sadhna_reward_grants WHERE user_id = $1 AND milestone = $2`,
		userID, milestone,
	).Scan(&n)
	if err != nil {
		return false, fmt.Errorf("has milestone: %w", err)
	}
	return n > 0, nil
}

// CreateGrant records a gift for a milestone. The unique (user_id, milestone)
// makes it idempotent under races; a conflict is a no-op, not an error.
func (r *RewardRepo) CreateGrant(ctx context.Context, userID, rewardID string, milestone int) error {
	_, err := r.pg.Pool.Exec(ctx, `
		INSERT INTO sadhna_reward_grants (user_id, reward_id, milestone)
		VALUES ($1, $2, $3)
		ON CONFLICT (user_id, milestone) DO NOTHING`,
		userID, rewardID, milestone,
	)
	if err != nil {
		return fmt.Errorf("create grant: %w", err)
	}
	return nil
}

// PendingGrant returns the most recent grant the client hasn't celebrated
// yet (celebrated_at IS NULL), or nil. Drives the one-time confetti.
func (r *RewardRepo) PendingGrant(ctx context.Context, userID string) (*model.SadhnaRewardGrant, error) {
	var g model.SadhnaRewardGrant
	err := r.pg.Pool.QueryRow(ctx, `
		SELECT g.milestone, g.granted_at,
		       w.id, w.key, w.name, w.meaning, w.image_url, w.active, w.sort
		FROM sadhna_reward_grants g
		JOIN sadhna_rewards w ON w.id = g.reward_id
		WHERE g.user_id = $1 AND g.celebrated_at IS NULL
		ORDER BY g.granted_at DESC, g.milestone DESC
		LIMIT 1`,
		userID,
	).Scan(
		&g.Milestone, &g.GrantedAt,
		&g.Reward.ID, &g.Reward.Key, &g.Reward.Name, &g.Reward.Meaning,
		&g.Reward.ImageURL, &g.Reward.Active, &g.Reward.Sort,
	)
	if err != nil {
		return nil, nil // no rows / nothing pending
	}
	return &g, nil
}

// MarkCelebrated clears all of the user's pending celebrations.
func (r *RewardRepo) MarkCelebrated(ctx context.Context, userID string) error {
	_, err := r.pg.Pool.Exec(ctx, `
		UPDATE sadhna_reward_grants SET celebrated_at = $1
		WHERE user_id = $2 AND celebrated_at IS NULL`,
		time.Now().UTC(), userID,
	)
	if err != nil {
		return fmt.Errorf("mark celebrated: %w", err)
	}
	return nil
}