package store

import (
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
)

// Note 笔记实体。DeletedAt 非 nil 表示处于回收站（软删除）。
type Note struct {
	ID        int64    `json:"id"`
	Slug      string   `json:"slug"`
	Title     string   `json:"title"`
	Summary   string   `json:"summary"`
	Content   string   `json:"content,omitempty"`
	Status    string   `json:"status"`
	Tags      []string `json:"tags"`
	Pinned    bool     `json:"pinned"`
	DeletedAt *int64   `json:"deleted_at,omitempty"`
	CreatedAt int64    `json:"created_at"`
	UpdatedAt int64    `json:"updated_at"`
}

// ErrNotFound 统一的「不存在」错误。
var ErrNotFound = errors.New("not found")

const noteColumns = "id, slug, title, summary, content, status, tags, pinned, deleted_at, created_at, updated_at"

func scanNote(scan func(dest ...any) error) (*Note, error) {
	var n Note
	var tagsJSON string
	var pinned int
	var content string
	if err := scan(&n.ID, &n.Slug, &n.Title, &n.Summary, &content, &n.Status, &tagsJSON, &pinned, &n.DeletedAt, &n.CreatedAt, &n.UpdatedAt); err != nil {
		return nil, err
	}
	n.Content = content
	n.Pinned = pinned != 0
	if err := json.Unmarshal([]byte(tagsJSON), &n.Tags); err != nil {
		n.Tags = []string{}
	}
	if n.Tags == nil {
		n.Tags = []string{}
	}
	return &n, nil
}

// CreateNote 新建笔记，返回 id。
func (s *Store) CreateNote(n *Note) (int64, error) {
	tags, err := marshalTags(n.Tags)
	if err != nil {
		return 0, err
	}
	res, err := s.db.Exec(
		`INSERT INTO notes (slug, title, summary, content, status, tags, pinned, created_at, updated_at)
		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		n.Slug, n.Title, n.Summary, n.Content, n.Status, tags, boolToInt(n.Pinned), n.CreatedAt, n.UpdatedAt)
	if err != nil {
		return 0, err
	}
	return res.LastInsertId()
}

// UpdateNote 更新笔记内容字段（不含 slug 冲突裁决，见 httpapi 层）。
func (s *Store) UpdateNote(n *Note) error {
	tags, err := marshalTags(n.Tags)
	if err != nil {
		return err
	}
	res, err := s.db.Exec(
		`UPDATE notes SET title=?, summary=?, content=?, status=?, tags=?, pinned=?, updated_at=? WHERE id=? AND deleted_at IS NULL`,
		n.Title, n.Summary, n.Content, n.Status, tags, boolToInt(n.Pinned), n.UpdatedAt, n.ID)
	if err != nil {
		return err
	}
	if rows, _ := res.RowsAffected(); rows == 0 {
		return ErrNotFound
	}
	return nil
}

// UpdateNoteSlug 修改 slug（仅正常态笔记）。
func (s *Store) UpdateNoteSlug(id int64, slug string, updatedAt int64) error {
	res, err := s.db.Exec(`UPDATE notes SET slug=?, updated_at=? WHERE id=? AND deleted_at IS NULL`, slug, updatedAt, id)
	if err != nil {
		return err
	}
	if rows, _ := res.RowsAffected(); rows == 0 {
		return ErrNotFound
	}
	return nil
}

// SoftDeleteNote 置 deleted_at（回收站）。refs 不动（§6.2）。
func (s *Store) SoftDeleteNote(id int64, at int64) error {
	res, err := s.db.Exec(`UPDATE notes SET deleted_at=? WHERE id=? AND deleted_at IS NULL`, at, id)
	if err != nil {
		return err
	}
	if rows, _ := res.RowsAffected(); rows == 0 {
		return ErrNotFound
	}
	return nil
}

// RestoreNote 清空 deleted_at。
func (s *Store) RestoreNote(id int64) error {
	res, err := s.db.Exec(`UPDATE notes SET deleted_at=NULL WHERE id=? AND deleted_at IS NOT NULL`, id)
	if err != nil {
		return err
	}
	if rows, _ := res.RowsAffected(); rows == 0 {
		return ErrNotFound
	}
	return nil
}

// GetNoteByID 按 id 取（含回收站）。
func (s *Store) GetNoteByID(id int64) (*Note, error) {
	row := s.db.QueryRow(`SELECT `+noteColumns+` FROM notes WHERE id=?`, id)
	n, err := scanNote(row.Scan)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrNotFound
	}
	return n, err
}

// GetNoteBySlug 按 slug 取（含回收站；可见性裁决在调用方）。
func (s *Store) GetNoteBySlug(slug string) (*Note, error) {
	row := s.db.QueryRow(`SELECT `+noteColumns+` FROM notes WHERE slug=?`, slug)
	n, err := scanNote(row.Scan)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrNotFound
	}
	return n, err
}

// SlugExists slug 是否已被占用（**含回收站**，§6.2：回收期内 slug 仍被占用）。
// excludeID 用于更新场景排除自身；传 0 表示不排除。
func (s *Store) SlugExists(slug string, excludeID int64) (bool, error) {
	var one int
	err := s.db.QueryRow(`SELECT 1 FROM notes WHERE slug=? AND id<>? LIMIT 1`, slug, excludeID).Scan(&one)
	if errors.Is(err, sql.ErrNoRows) {
		return false, nil
	}
	return err == nil, err
}

// PublicNoteFilter 可见性过滤的统一谓词（§9.1-T10 单一可信点）。
const PublicNoteFilter = "status='public' AND deleted_at IS NULL"

// ListPublicNotes 公开笔记分页列表（不含全文）。tag 非空时按标签过滤。
func (s *Store) ListPublicNotes(page, pageSize int, tag string) ([]Note, int, error) {
	where := PublicNoteFilter
	args := []any{}
	if tag != "" {
		// json_each 参数化过滤，无拼接注入面。
		where += ` AND EXISTS (SELECT 1 FROM json_each(n.tags) je WHERE je.value = ?)`
		args = append(args, tag)
	}
	var total int
	if err := s.db.QueryRow(`SELECT COUNT(*) FROM notes n WHERE `+where, args...).Scan(&total); err != nil {
		return nil, 0, err
	}
	q := `SELECT n.id, n.slug, n.title, n.summary, '' AS content, n.status, n.tags, n.pinned, n.deleted_at, n.created_at, n.updated_at
	      FROM notes n WHERE ` + where + `
	      ORDER BY n.pinned DESC, n.updated_at DESC, n.id DESC LIMIT ? OFFSET ?`
	rows, err := s.db.Query(q, append(args, pageSize, (page-1)*pageSize)...)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()
	var out []Note
	for rows.Next() {
		n, err := scanNote(rows.Scan)
		if err != nil {
			return nil, 0, err
		}
		out = append(out, *n)
	}
	return out, total, rows.Err()
}

// AdjacentPublicNote 返回公开序列中与 n 相邻的上一篇/下一篇
// （按列表序 updated_at DESC, id DESC）。仅返回 slug 与 title。
func (s *Store) AdjacentPublicNote(n *Note, dir string) (slug, title string, err error) {
	var q string
	switch dir {
	case "prev": // 列表中更早的一篇
		q = `SELECT slug, title FROM notes WHERE ` + PublicNoteFilter + `
		     AND (updated_at > ? OR (updated_at = ? AND id < ?))
		     ORDER BY updated_at ASC, id DESC LIMIT 1`
	case "next": // 列表中更新的一篇
		q = `SELECT slug, title FROM notes WHERE ` + PublicNoteFilter + `
		     AND (updated_at < ? OR (updated_at = ? AND id > ?))
		     ORDER BY updated_at DESC, id ASC LIMIT 1`
	default:
		return "", "", fmt.Errorf("dir 必须为 prev|next")
	}
	row := s.db.QueryRow(q, n.UpdatedAt, n.UpdatedAt, n.ID)
	if err := row.Scan(&slug, &title); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return "", "", nil
		}
		return "", "", err
	}
	return slug, title, nil
}

// ListPublicNotesFull 公开笔记列表（**含全文**，RSS/渲染用），上限 limit 条。
func (s *Store) ListPublicNotesFull(limit int) ([]Note, error) {
	q := `SELECT ` + noteColumns + ` FROM notes WHERE ` + PublicNoteFilter + `
	      ORDER BY updated_at DESC, id DESC LIMIT ?`
	rows, err := s.db.Query(q, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []Note{}
	for rows.Next() {
		n, err := scanNote(rows.Scan)
		if err != nil {
			return nil, err
		}
		out = append(out, *n)
	}
	return out, rows.Err()
}

// ListAdminNotes 全部正常笔记（含私有，不含回收站），不含全文。
func (s *Store) ListAdminNotes() ([]Note, error) {
	q := `SELECT id, slug, title, summary, '' AS content, status, tags, pinned, deleted_at, created_at, updated_at
	      FROM notes WHERE deleted_at IS NULL
	      ORDER BY pinned DESC, updated_at DESC, id DESC`
	return s.queryNotes(q)
}

// ListTrash 回收站列表（软删除中），不含全文。
func (s *Store) ListTrash() ([]Note, error) {
	q := `SELECT id, slug, title, summary, '' AS content, status, tags, pinned, deleted_at, created_at, updated_at
	      FROM notes WHERE deleted_at IS NOT NULL
	      ORDER BY deleted_at DESC`
	return s.queryNotes(q)
}

// ListExpiredTrash 过期待物理删除的笔记 id（gc 用）。
func (s *Store) ListExpiredTrash(before int64) ([]int64, error) {
	rows, err := s.db.Query(`SELECT id FROM notes WHERE deleted_at IS NOT NULL AND deleted_at < ?`, before)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var ids []int64
	for rows.Next() {
		var id int64
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		ids = append(ids, id)
	}
	return ids, rows.Err()
}

// DeleteNoteForever 物理删除（refs 级联，需 foreign_keys=1）。
func (s *Store) DeleteNoteForever(id int64) error {
	res, err := s.db.Exec(`DELETE FROM notes WHERE id=?`, id)
	if err != nil {
		return err
	}
	if rows, _ := res.RowsAffected(); rows == 0 {
		return ErrNotFound
	}
	return nil
}

// TagCount 标签聚合项。
type TagCount struct {
	Name  string `json:"name"`
	Count int    `json:"count"`
}

// PublicTags 仅统计公开且未删除笔记的标签（§7.1 /api/tags）。
func (s *Store) PublicTags() ([]TagCount, error) {
	rows, err := s.db.Query(`
		SELECT je.value AS tag, COUNT(*) AS cnt
		FROM notes n, json_each(n.tags) je
		WHERE ` + PublicNoteFilter + `
		GROUP BY je.value
		ORDER BY cnt DESC, tag ASC`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []TagCount
	for rows.Next() {
		var tc TagCount
		if err := rows.Scan(&tc.Name, &tc.Count); err != nil {
			return nil, err
		}
		out = append(out, tc)
	}
	return out, rows.Err()
}

func (s *Store) queryNotes(q string, args ...any) ([]Note, error) {
	rows, err := s.db.Query(q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []Note{}
	for rows.Next() {
		n, err := scanNote(rows.Scan)
		if err != nil {
			return nil, err
		}
		out = append(out, *n)
	}
	return out, rows.Err()
}

func marshalTags(tags []string) (string, error) {
	if tags == nil {
		tags = []string{}
	}
	b, err := json.Marshal(tags)
	if err != nil {
		return "", err
	}
	return string(b), nil
}

func boolToInt(b bool) int {
	if b {
		return 1
	}
	return 0
}

// NormalizeTags 清洗标签：去空白、去空、去重、上限 20 个、单个 ≤64 字符。
func NormalizeTags(tags []string) []string {
	seen := map[string]bool{}
	out := []string{}
	for _, t := range tags {
		t = strings.TrimSpace(t)
		if t == "" || seen[t] {
			continue
		}
		if len([]rune(t)) > 64 {
			t = string([]rune(t)[:64])
		}
		seen[t] = true
		out = append(out, t)
		if len(out) >= 20 {
			break
		}
	}
	return out
}