package service

import (
	"errors"
	"fmt"
	"slices"
	"spend-sparrow/internal/db"
	"spend-sparrow/internal/log"
	"spend-sparrow/internal/types"

	"github.com/google/uuid"
	"github.com/jmoiron/sqlx"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
)

var (
	treasureChestMetric = promauto.NewCounterVec(
		prometheus.CounterOpts{
			Name: "spendsparrow_treasurechest_total",
			Help: "The total of treasurechest operations",
		},
		[]string{"operation"},
	)
)

type TreasureChest interface {
	Add(user *types.User, parentId, name string) (*types.TreasureChest, error)
	Update(user *types.User, id, parentId, name string) (*types.TreasureChest, error)
	Get(user *types.User, id string) (*types.TreasureChest, error)
	GetAll(user *types.User) ([]*types.TreasureChest, error)
	Delete(user *types.User, id string) error
}

type TreasureChestImpl struct {
	db     *sqlx.DB
	clock  Clock
	random Random
}

func NewTreasureChest(db *sqlx.DB, random Random, clock Clock) TreasureChest {
	return TreasureChestImpl{
		db:     db,
		clock:  clock,
		random: random,
	}
}

func (s TreasureChestImpl) Add(user *types.User, parentId, name string) (*types.TreasureChest, error) {
	treasureChestMetric.WithLabelValues("add").Inc()

	if user == nil {
		return nil, ErrUnauthorized
	}

	newId, err := s.random.UUID()
	if err != nil {
		return nil, types.ErrInternal
	}

	err = validateString(name, "name")
	if err != nil {
		return nil, err
	}

	var parentUuid *uuid.UUID
	if parentId != "" {
		parent, err := s.Get(user, parentId)
		if err != nil {
			return nil, err
		}
		if parent.ParentId != nil {
			return nil, fmt.Errorf("only a depth of 1 allowed: %w", ErrBadRequest)
		}
		parentUuid = &parent.Id
	}

	treasureChest := &types.TreasureChest{
		Id:       newId,
		ParentId: parentUuid,
		UserId:   user.Id,

		Name: name,

		CurrentBalance: 0,

		CreatedAt: s.clock.Now(),
		CreatedBy: user.Id,
		UpdatedAt: nil,
		UpdatedBy: nil,
	}

	r, err := s.db.NamedExec(`
		INSERT INTO treasure_chest (id, parent_id, user_id, name, current_balance, created_at, created_by) 
		VALUES (:id, :parent_id, :user_id, :name, :current_balance, :created_at, :created_by)`, treasureChest)
	err = db.TransformAndLogDbError("treasureChest Insert", r, err)
	if err != nil {
		return nil, err
	}

	return treasureChest, nil
}

func (s TreasureChestImpl) Update(user *types.User, idStr, parentId, name string) (*types.TreasureChest, error) {
	treasureChestMetric.WithLabelValues("update").Inc()
	if user == nil {
		return nil, ErrUnauthorized
	}
	err := validateString(name, "name")
	if err != nil {
		return nil, err
	}
	id, err := uuid.Parse(idStr)
	if err != nil {
		log.Error("treasureChest update: %v", err)
		return nil, fmt.Errorf("could not parse Id: %w", ErrBadRequest)
	}

	tx, err := s.db.Beginx()
	err = db.TransformAndLogDbError("treasureChest Update", nil, err)
	if err != nil {
		return nil, err
	}
	defer func() {
		_ = tx.Rollback()
	}()

	treasureChest := &types.TreasureChest{}
	err = tx.Get(treasureChest, `SELECT * FROM treasure_chest WHERE user_id = ? AND id = ?`, user.Id, id)
	err = db.TransformAndLogDbError("treasureChest Update", nil, err)
	if err != nil {
		if errors.Is(err, db.ErrNotFound) {
			return nil, fmt.Errorf("treasureChest %v not found: %w", idStr, err)
		}
		return nil, types.ErrInternal
	}

	var parentUuid *uuid.UUID
	if parentId != "" {
		parent, err := s.Get(user, parentId)
		if err != nil {
			return nil, err
		}
		var childCount int
		err = tx.Get(&childCount, `SELECT COUNT(*) FROM treasure_chest WHERE user_id = ? AND parent_id = ?`, user.Id, id)
		err = db.TransformAndLogDbError("treasureChest Update", nil, err)
		if err != nil {
			return nil, err
		}
		if parent.ParentId != nil || childCount > 0 {
			return nil, fmt.Errorf("only one level allowed: %w", ErrBadRequest)
		}

		parentUuid = &parent.Id
	}

	timestamp := s.clock.Now()
	treasureChest.Name = name
	treasureChest.ParentId = parentUuid
	treasureChest.UpdatedAt = &timestamp
	treasureChest.UpdatedBy = &user.Id

	r, err := tx.NamedExec(`
		UPDATE treasure_chest 
		SET
			parent_id = :parent_id,
			name = :name,
			current_balance = :current_balance,
			updated_at = :updated_at,
			updated_by = :updated_by
		WHERE id = :id
			AND user_id = :user_id`, treasureChest)
	err = db.TransformAndLogDbError("treasureChest Update", r, err)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	err = db.TransformAndLogDbError("treasureChest Update", nil, err)
	if err != nil {
		return nil, err
	}

	return treasureChest, nil
}

func (s TreasureChestImpl) Get(user *types.User, id string) (*types.TreasureChest, error) {
	treasureChestMetric.WithLabelValues("get").Inc()

	if user == nil {
		return nil, ErrUnauthorized
	}
	uuid, err := uuid.Parse(id)
	if err != nil {
		log.Error("treasureChest get: %v", err)
		return nil, fmt.Errorf("could not parse Id: %w", ErrBadRequest)
	}

	var treasureChest types.TreasureChest
	err = s.db.Get(&treasureChest, `SELECT * FROM treasure_chest WHERE user_id = ? AND id = ?`, user.Id, uuid)
	err = db.TransformAndLogDbError("treasureChest Get", nil, err)
	if err != nil {
		if errors.Is(err, db.ErrNotFound) {
			return nil, fmt.Errorf("treasureChest %v not found: %w", id, err)
		}
		return nil, types.ErrInternal
	}

	return &treasureChest, nil
}

func (s TreasureChestImpl) GetAll(user *types.User) ([]*types.TreasureChest, error) {
	treasureChestMetric.WithLabelValues("get_all").Inc()
	if user == nil {
		return nil, ErrUnauthorized
	}

	treasureChests := make([]*types.TreasureChest, 0)
	err := s.db.Select(&treasureChests, `SELECT * FROM treasure_chest WHERE user_id = ?`, user.Id)
	err = db.TransformAndLogDbError("treasureChest GetAll", nil, err)
	if err != nil {
		return nil, err
	}

	return sortTree(treasureChests), nil
}

func (s TreasureChestImpl) Delete(user *types.User, idStr string) error {
	treasureChestMetric.WithLabelValues("delete").Inc()
	if user == nil {
		return ErrUnauthorized
	}
	id, err := uuid.Parse(idStr)
	if err != nil {
		log.Error("treasureChest delete: %v", err)
		return fmt.Errorf("could not parse Id: %w", ErrBadRequest)
	}

	tx, err := s.db.Beginx()
	err = db.TransformAndLogDbError("treasureChest Delete", nil, err)
	if err != nil {
		return nil
	}
	defer func() {
		_ = tx.Rollback()
	}()

	childCount := 0
	err = tx.Get(&childCount, `SELECT COUNT(*) FROM treasure_chest WHERE user_id = ? AND parent_id = ?`, user.Id, id)
	err = db.TransformAndLogDbError("treasureChest Delete", nil, err)
	if err != nil {
		return err
	}

	if childCount > 0 {
		return fmt.Errorf("treasure chest has children: %w", ErrBadRequest)
	}

	transactionsCount := 0
	err = tx.Get(&transactionsCount,
		`SELECT COUNT(*) FROM "transaction" WHERE user_id = ? AND treasure_chest_id = ?`,
		user.Id, id)
	err = db.TransformAndLogDbError("treasureChest Delete", nil, err)
	if err != nil {
		return err
	}
	if transactionsCount > 0 {
		return fmt.Errorf("treasure chest has transactions: %w", ErrBadRequest)
	}

	r, err := tx.Exec(`DELETE FROM treasure_chest WHERE id = ? AND user_id = ?`, id, user.Id)
	err = db.TransformAndLogDbError("treasureChest Delete", r, err)
	if err != nil {
		return err
	}

	err = tx.Commit()
	err = db.TransformAndLogDbError("treasureChest Delete", nil, err)
	if err != nil {
		return err
	}

	return nil
}

func sortTree(nodes []*types.TreasureChest) []*types.TreasureChest {
	var (
		roots []*types.TreasureChest
	)
	children := make(map[uuid.UUID][]*types.TreasureChest)
	result := make([]*types.TreasureChest, 0)

	for _, node := range nodes {
		if node.ParentId == nil {
			roots = append(roots, node)
		} else {
			children[*node.ParentId] = append(children[*node.ParentId], node)
		}
	}

	slices.SortFunc(roots, func(a, b *types.TreasureChest) int {
		return compareStrings(a.Name, b.Name)
	})

	for _, root := range roots {
		result = append(result, root)

		childList := children[root.Id]

		slices.SortFunc(childList, func(a, b *types.TreasureChest) int {
			return compareStrings(a.Name, b.Name)
		})
		result = append(result, childList...)
	}

	return result
}

func compareStrings(a, b string) int {
	if a == b {
		return 0
	}
	if a < b {
		return -1
	}
	return 1
}