package memory

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
	"time"
)

// 本文件是记忆整理的存储层：分区扫描、候选落库与查询、运行留痕。它复用
// memory 包既有的 *sql.DB 与格式化辅助（formatTime/parseTime/scanItem），
// 不新建存储机制。
//
// 第一版唯一的写入就是候选表与运行表：**没有任何一条 memory_items 会被改写
// 或删除**（design/23 §3 非目标 + §7「apply 才写记忆」）。

// tidyCandidatePending 是候选的初始状态（design/23 §10）。
const tidyCandidatePending = "pending"

// tidyPartition 是整理的隔离单元：design/23 §6 的分区键
// (persona_id, scope, project_id)。分区之间**永不比较**。
type tidyPartition struct {
	personaID string
	scope     Scope
	projectID string
}

// label 渲染分区标签，供日志与截断登记使用（不含任何记忆正文）。
func (p tidyPartition) label() string {
	return fmt.Sprintf("%s/%s/%s", p.personaID, p.scope, p.projectID)
}

// tidyStatusActive 是「在册」状态。整理只扫描在册条目：已合并/已归档的行
// 不再参与比对（design §10 status 列）。
const tidyStatusActive = "active"

// listTidyPartitionItemsSQL 按分区读取**在册**（status='active'）条目，
// 最新在前；rowid 打破 created_at 并列，使同一刻写入的条目顺序稳定
// （与 ListByPersona 同一口径）。分区过滤写在 SQL 里，而不是读全表再在内存
// 里筛 —— design/23 §6 要求在分区切分层就隔断。
const listTidyPartitionItemsSQL = `SELECT id, persona_id, role_id, project_id, scope, kind,
	content, tags, confidence, source_conversation, created_at, updated_at,
	decay_weight FROM memory_items
	WHERE persona_id = ? AND scope = ? AND project_id = ? AND status = ?
	ORDER BY created_at DESC, rowid DESC LIMIT ?`

const listTidyPartitionsSQL = `SELECT DISTINCT persona_id, scope, project_id
	FROM memory_items WHERE status = ?
	ORDER BY persona_id, scope, project_id`

const countTidyPartitionItemsSQL = `SELECT COUNT(*) FROM memory_items
	WHERE persona_id = ? AND scope = ? AND project_id = ? AND status = ?`

const insertTidyCandidateSQL = `INSERT OR IGNORE INTO memory_tidy_candidates
	(id, persona_id, scope, project_id, kind, action, source_ids, target_id,
	 proposed_content, merged_content, reason, evidence, rule_version,
	 score_min, score_max, status, idempotency_key, created_at, decided_at, decided_by)
	VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, '', '')`

const insertTidyRunSQL = `INSERT INTO memory_tidy_runs
	(id, started_at, finished_at, scanned, candidates, applied, skipped, errors,
	 vetoed, veto_reasons, rule_version)
	VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`

const listTidyCandidatesSQL = `SELECT id, persona_id, scope, project_id, kind, action,
	source_ids, target_id, proposed_content, merged_content, reason, evidence,
	rule_version, score_min, score_max, status, idempotency_key, created_at
	FROM memory_tidy_candidates
	WHERE status = ?
	ORDER BY created_at DESC, rowid DESC LIMIT ?`

const listTidyRunsSQL = `SELECT id, started_at, finished_at, scanned, candidates,
	applied, skipped, errors, vetoed, veto_reasons, rule_version
	FROM memory_tidy_runs ORDER BY started_at DESC, rowid DESC LIMIT ?`

// listTidyPartitions 返回所有含在册条目的分区。DISTINCT 让每个分区的
// 扫描上限（design §9 每分区 5000 条）各自独立。
func (s *Store) listTidyPartitions(ctx context.Context) ([]tidyPartition, error) {
	rows, err := s.db.QueryContext(ctx, listTidyPartitionsSQL, string(tidyStatusActive))
	if err != nil {
		return nil, fmt.Errorf("memory: list tidy partitions: %w", err)
	}
	defer func() { _ = rows.Close() }()

	parts := make([]tidyPartition, 0)
	for rows.Next() {
		var p tidyPartition
		var scope string
		if err := rows.Scan(&p.personaID, &scope, &p.projectID); err != nil {
			return nil, fmt.Errorf("memory: scan tidy partition: %w", err)
		}
		p.scope = Scope(scope)
		parts = append(parts, p)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("memory: iterate tidy partitions: %w", err)
	}
	return parts, nil
}

// listTidyPartitionItems 读取一个分区内的在册条目（最新在前，最多 limit 条）。
func (s *Store) listTidyPartitionItems(ctx context.Context, p tidyPartition, limit int) ([]MemoryItem, error) {
	rows, err := s.db.QueryContext(ctx, listTidyPartitionItemsSQL,
		p.personaID, string(p.scope), p.projectID, string(tidyStatusActive), limit)
	if err != nil {
		return nil, fmt.Errorf("memory: list tidy partition items: %w", err)
	}
	return scanItems(rows, "tidy partition item")
}

// countTidyPartitionItems 数一个分区里在册条目的**真总数**。只在扫描上限命中时
// 调用一次：日志里的「总数」必须是真数，而不是被 LIMIT 截出来的 len(items)
// （那是**下限**，把「至少 5000」写成「正好 5000」就是一句谎）。
func (s *Store) countTidyPartitionItems(ctx context.Context, p tidyPartition) (int, error) {
	var total int
	if err := s.db.QueryRowContext(ctx, countTidyPartitionItemsSQL,
		p.personaID, string(p.scope), p.projectID, string(tidyStatusActive)).Scan(&total); err != nil {
		return 0, fmt.Errorf("memory: count tidy partition items: %w", err)
	}
	return total, nil
}

// insertTidyCandidate 落库一条候选，返回它是否是**新建**的。幂等键
// （design/23 §9）唯一：同一批数据重复运行命中已存在行时返回 (false, nil)，
// 绝不重复产候选。
func (s *Store) insertTidyCandidate(ctx context.Context, c TidyCandidate) (bool, error) {
	c.IdempotencyKey = tidyIdempotencyKey(c)
	sourceJSON, err := json.Marshal(c.SourceIDs)
	if err != nil {
		return false, fmt.Errorf("memory: encode tidy source ids: %w", err)
	}
	evidenceJSON, err := json.Marshal(c.Evidence)
	if err != nil {
		return false, fmt.Errorf("memory: encode tidy evidence: %w", err)
	}
	if c.CreatedAt.IsZero() {
		c.CreatedAt = time.Now().UTC()
	}
	res, err := s.db.ExecContext(ctx, insertTidyCandidateSQL,
		c.ID, c.PersonaID, string(c.Scope), c.ProjectID, string(c.Kind), string(c.Action),
		string(sourceJSON), c.TargetID, c.ProposedContent, c.MergedContent, c.Reason,
		string(evidenceJSON), c.RuleVersion, c.ScoreMin, c.ScoreMax, c.Status,
		c.IdempotencyKey, formatTime(c.CreatedAt))
	if err != nil {
		return false, fmt.Errorf("memory: insert tidy candidate: %w", err)
	}
	n, err := res.RowsAffected()
	if err != nil {
		return false, fmt.Errorf("memory: tidy candidate rows affected: %w", err)
	}
	return n > 0, nil
}

// persistTidyRun 写一条运行留痕（design/23 §10 memory_tidy_runs）。
func (s *Store) persistTidyRun(ctx context.Context, run TidyRun) error {
	if run.ID == "" {
		run.ID = mustNewTidyID()
	}
	reasons, err := json.Marshal(run.VetoReasons)
	if err != nil {
		return fmt.Errorf("memory: encode tidy veto reasons: %w", err)
	}
	if _, err := s.db.ExecContext(ctx, insertTidyRunSQL,
		run.ID, formatTime(run.StartedAt), formatTime(run.FinishedAt),
		run.Scanned, run.Candidates, run.Applied, run.Skipped, run.Errors,
		run.Vetoed, string(reasons), run.RuleVersion); err != nil {
		return fmt.Errorf("memory: insert tidy run: %w", err)
	}
	return nil
}

// ListTidyCandidates 返回指定状态的整理候选（最新在前，最多 limit 条，
// 非正 limit 取 defaultTidyCandidateLimit）。它是读侧入口：候选正文含隐私，
// 只应由 owner-only 的读侧使用（design/23 §11）。
func (s *Store) ListTidyCandidates(ctx context.Context, status string, limit int) ([]TidyCandidate, error) {
	if strings.TrimSpace(status) == "" {
		status = tidyCandidatePending
	}
	if limit <= 0 {
		limit = defaultTidyCandidateLimit
	}
	rows, err := s.db.QueryContext(ctx, listTidyCandidatesSQL, status, limit)
	if err != nil {
		return nil, fmt.Errorf("memory: list tidy candidates: %w", err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]TidyCandidate, 0)
	for rows.Next() {
		c, err := scanTidyCandidate(rows)
		if err != nil {
			return nil, fmt.Errorf("memory: scan tidy candidate: %w", err)
		}
		out = append(out, c)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("memory: iterate tidy candidates: %w", err)
	}
	return out, nil
}

// ListTidyRuns 返回整理运行留痕（最新在前，最多 limit 条）。非正 limit 取
// 一个保守的默认条数。
func (s *Store) ListTidyRuns(ctx context.Context, limit int) ([]TidyRun, error) {
	if limit <= 0 {
		limit = defaultTidyCandidateLimit
	}
	rows, err := s.db.QueryContext(ctx, listTidyRunsSQL, limit)
	if err != nil {
		return nil, fmt.Errorf("memory: list tidy runs: %w", err)
	}
	defer func() { _ = rows.Close() }()

	out := make([]TidyRun, 0)
	for rows.Next() {
		var (
			r           TidyRun
			startedAt   string
			finishedAt  string
			reasonsJSON string
		)
		if err := rows.Scan(&r.ID, &startedAt, &finishedAt, &r.Scanned, &r.Candidates,
			&r.Applied, &r.Skipped, &r.Errors, &r.Vetoed, &reasonsJSON, &r.RuleVersion); err != nil {
			return nil, fmt.Errorf("memory: scan tidy run: %w", err)
		}
		var err error
		if r.StartedAt, err = parseTime(startedAt); err != nil {
			return nil, err
		}
		if r.FinishedAt, err = parseTime(finishedAt); err != nil {
			return nil, err
		}
		if err := json.Unmarshal([]byte(reasonsJSON), &r.VetoReasons); err != nil {
			return nil, fmt.Errorf("memory: decode tidy veto reasons: %w", err)
		}
		out = append(out, r)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("memory: iterate tidy runs: %w", err)
	}
	return out, nil
}

// scanTidyCandidate 读取一行候选：source_ids 与 evidence 以 JSON 存储。
func scanTidyCandidate(sc rowScanner) (TidyCandidate, error) {
	var (
		c           TidyCandidate
		scope, kind string
		action      string
		sourceJSON  string
		evidenceRaw string
		createdAt   string
	)
	if err := sc.Scan(&c.ID, &c.PersonaID, &scope, &c.ProjectID, &kind, &action,
		&sourceJSON, &c.TargetID, &c.ProposedContent, &c.MergedContent, &c.Reason,
		&evidenceRaw, &c.RuleVersion, &c.ScoreMin, &c.ScoreMax, &c.Status,
		&c.IdempotencyKey, &createdAt); err != nil {
		return TidyCandidate{}, err
	}
	c.Scope = Scope(scope)
	c.Kind = Kind(kind)
	c.Action = TidyAction(action)
	if err := json.Unmarshal([]byte(sourceJSON), &c.SourceIDs); err != nil {
		return TidyCandidate{}, fmt.Errorf("memory: decode tidy source ids: %w", err)
	}
	if c.SourceIDs == nil {
		c.SourceIDs = []string{}
	}
	if err := json.Unmarshal([]byte(evidenceRaw), &c.Evidence); err != nil {
		return TidyCandidate{}, fmt.Errorf("memory: decode tidy evidence: %w", err)
	}
	t, err := parseTime(createdAt)
	if err != nil {
		return TidyCandidate{}, err
	}
	c.CreatedAt = t
	return c, nil
}