MailUI4Agents/gateway/internal/repo/repo.go

package repo

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/agentmail/gateway/internal/db"
	"github.com/agentmail/gateway/internal/models"
	"github.com/google/uuid"
)

// ---------- Agent ----------

func CreateOrUpdateAgent(ctx context.Context, name, secret, platform string, workspaces []models.Workspace) error {
	wsJSON, _ := json.Marshal(workspaces)
	// 注意 DO UPDATE 里【不】碰 default_rounds：
	// 那是管理员配的值，Agent 重启重新注册不应该把它冲回默认。
	_, err := db.DB.ExecContext(ctx, `
		INSERT INTO agents (agent_name, secret, workspaces, platform, status, last_seen)
		VALUES ($1, $2, $3, $4, 'online', NOW())
		ON CONFLICT (agent_name) DO UPDATE SET
			secret = EXCLUDED.secret,
			workspaces = EXCLUDED.workspaces,
			platform = EXCLUDED.platform,
			status = 'online',
			last_seen = NOW()
	`, name, secret, wsJSON, platform)
	return err
}

func HeartbeatAgent(ctx context.Context, agentName string) (int, error) {
	_, err := db.DB.ExecContext(ctx,
		`UPDATE agents SET last_seen = NOW(), status = 'online' WHERE agent_name = $1`,
		agentName)
	if err != nil {
		return 0, err
	}
	return CountUnread(ctx, agentName)
}

func ListAgents(ctx context.Context, statusFilter string) ([]models.Agent, error) {
	// 带上 default_rounds：前端补全收件人时要显示「派给它的任务默认几个来回」，
	// 否则人得先去管理员页查一遍才敢派活。
	q := `SELECT agent_id, agent_name, workspaces, platform, status,
	             COALESCE(default_rounds, 0) FROM agents`
	args := []any{}
	if statusFilter != "" {
		q += ` WHERE status = $1`
		args = append(args, statusFilter)
	}
	q += ` ORDER BY agent_name`

	rows, err := db.DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	agents := []models.Agent{}
	for rows.Next() {
		var a models.Agent
		var wsJSON []byte
		if err := rows.Scan(&a.ID, &a.Name, &wsJSON, &a.Platform, &a.Status,
			&a.DefaultRounds); err != nil {
			return nil, err
		}
		if wsJSON != nil {
			json.Unmarshal(wsJSON, &a.Workspaces)
		}
		agents = append(agents, a)
	}
	return agents, nil
}

func VerifyAgent(ctx context.Context, name, secret string) (*models.Agent, error) {
	var a models.Agent
	var wsJSON []byte
	err := db.DB.QueryRowContext(ctx,
		`SELECT agent_id, agent_name, workspaces, platform, status
		 FROM agents WHERE agent_name = $1 AND secret = $2`,
		name, secret,
	).Scan(&a.ID, &a.Name, &wsJSON, &a.Platform, &a.Status)
	if err != nil {
		return nil, err
	}
	if wsJSON != nil {
		json.Unmarshal(wsJSON, &a.Workspaces)
	}
	return &a, nil
}

// ---------- Session ----------

// CreateSession 建会话。
//
// 显式传了 alias（发信时的 session_alias 参数）= 调用方亲自命名，标为 manual，
// 平台后续自动同步不得覆盖；未传则等待平台命名，标为 platform。
func CreateSession(ctx context.Context, alias *string, fromAgent, subject string) (uuid.UUID, error) {
	source := "platform"
	if alias != nil && *alias != "" {
		source = "manual"
	}
	var id uuid.UUID
	err := db.DB.QueryRowContext(ctx,
		`INSERT INTO sessions (session_alias, from_agent, subject, alias_source)
		 VALUES ($1, $2, $3, $4) RETURNING session_id`,
		alias, fromAgent, subject, source,
	).Scan(&id)
	return id, err
}

func GetSessionByID(ctx context.Context, id uuid.UUID) (*models.Session, error) {
	var s models.Session
	var dismissed *string
	err := db.DB.QueryRowContext(ctx,
		`SELECT session_id, session_alias, from_agent, subject, status, owner_user_id,
		        created_at, updated_at, rename_dismissed, COALESCE(alias_source, 'platform'),
		        COALESCE(max_rounds, 0), COALESCE(used_rounds, 0)
		 FROM sessions WHERE session_id = $1`, id,
	).Scan(&s.ID, &s.Alias, &s.FromAgent, &s.Subject, &s.Status, &s.OwnerUserID,
		&s.CreatedAt, &s.UpdatedAt, &dismissed, &s.AliasSource,
		&s.MaxRounds, &s.UsedRounds)
	if err != nil {
		return nil, err
	}
	if dismissed != nil {
		s.RenameDismissed = *dismissed
	}
	return &s, nil
}

func TouchSession(ctx context.Context, id uuid.UUID) error {
	_, err := db.DB.ExecContext(ctx,
		`UPDATE sessions SET updated_at = NOW(), status = 'active' WHERE session_id = $1`, id)
	return err
}

// UpdateSessionAlias 手工改名（人显式指定）。
//
// 同时把 alias_source 标为 'manual'：人的选择优先于平台自动命名。
// 否则平台下一次 session.updated 会把人刚定的名字冲掉，
// 人上一秒记住的寻址地址下一秒失效。
func UpdateSessionAlias(ctx context.Context, id uuid.UUID, alias string) error {
	_, err := db.DB.ExecContext(ctx,
		`UPDATE sessions SET session_alias = $1, alias_source = 'manual', updated_at = NOW()
		 WHERE session_id = $2`,
		alias, id)
	return err
}

func ListSessions(ctx context.Context, statusFilter string, limit int) ([]models.Session, error) {
	q := `SELECT s.session_id, s.session_alias, s.from_agent, s.subject, s.status,
	               s.owner_user_id, s.created_at, s.updated_at,
	               (SELECT COUNT(*) FROM mails m WHERE m.session_id = s.session_id)
	      FROM sessions s`
	args := []any{}
	if statusFilter != "" {
		q += ` WHERE s.status = $1`
		args = append(args, statusFilter)
	}
	q += ` ORDER BY s.updated_at DESC`
	if limit > 0 {
		q += fmt.Sprintf(` LIMIT %d`, limit)
	}

	rows, err := db.DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	sessions := []models.Session{}
	for rows.Next() {
		var s models.Session
		if err := rows.Scan(&s.ID, &s.Alias, &s.FromAgent, &s.Subject, &s.Status,
			&s.OwnerUserID, &s.CreatedAt, &s.UpdatedAt,
			&s.MaxRounds, &s.UsedRounds, &s.MailCount); err != nil {
			return nil, err
		}
		sessions = append(sessions, s)
	}
	return sessions, rows.Err()
}

// ---------- Mail ----------

func CreateMail(ctx context.Context, sessionID uuid.UUID, parentMailID *uuid.UUID,
	fromName, fromWorkspace, toName, toWorkspace, subject, body string, ccList []models.Address) (uuid.UUID, error) {
	if ccList == nil {
		ccList = []models.Address{}
	}
	ccJSON, _ := json.Marshal(ccList)
	var id uuid.UUID
	err := db.DB.QueryRowContext(ctx,
		// created_at 显式给 NOW()：SQLite 的 DEFAULT CURRENT_TIMESTAMP 只有秒精度，
		// 同秒插入的多封邮件排序不确定（「会话里最早/最后那封」都会取错行）。
		// 改 schema 的默认值只对新库生效 —— CREATE TABLE IF NOT EXISTS 不改已存在的表，
		// 而 SQLite 没有 ALTER COLUMN，因此这里显式传。
		`INSERT INTO mails (session_id, parent_mail_id, from_name, from_workspace,
		                    to_name, to_workspace, subject, body, cc_list, created_at)
		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, NOW()) RETURNING mail_id`,
		sessionID, parentMailID, fromName, fromWorkspace, toName, toWorkspace, subject, body, ccJSON,
	).Scan(&id)
	return id, err
}

// CreatePermissionMail 创建权限请求邮件，toUser 为目标人类用户名
func CreatePermissionMail(ctx context.Context, sessionID uuid.UUID, fromName, toUser, question, body string, options []string) (uuid.UUID, error) {
	optsJSON, _ := json.Marshal(options)
	var id uuid.UUID
	err := db.DB.QueryRowContext(ctx,
		`INSERT INTO mails (session_id, from_name, to_name, subject, body, mail_type, permission_options, created_at)
		 VALUES ($1, $2, $3, $4, $5, 'permission_request', $6, NOW()) RETURNING mail_id`,
		sessionID, fromName, toUser, "权限请求: "+question, body, optsJSON,
	).Scan(&id)
	return id, err
}

// CreateDecisionMail 创建人类决策邮件（fromUser → toAgent）
func CreateDecisionMail(ctx context.Context, sessionID uuid.UUID, parentMailID uuid.UUID, fromUser, toAgent, decision, note string) (uuid.UUID, error) {
	var id uuid.UUID
	body := decision
	if note != "" {
		body = fmt.Sprintf("%s\n\n备注: %s", decision, note)
	}
	err := db.DB.QueryRowContext(ctx,
		`INSERT INTO mails (session_id, parent_mail_id, from_name, to_name, subject, body, created_at)
		 VALUES ($1, $2, $3, $4, $5, $6, NOW()) RETURNING mail_id`,
		sessionID, parentMailID, fromUser, toAgent, "Re: 权限请求 - "+decision, body,
	).Scan(&id)
	return id, err
}

func GetMailByID(ctx context.Context, id uuid.UUID) (*models.Mail, error) {
	var m models.Mail
	var alias *string
	var ccJSON []byte
	var renameAlias, renameReason *string
	err := db.DB.QueryRowContext(ctx,
		`SELECT m.mail_id, m.session_id, m.parent_mail_id,
		        m.from_name, m.from_workspace, m.to_name, m.to_workspace,
		        m.cc_list, m.subject, m.body, m.mail_type, COALESCE(m.permission_result,'') AS permission_result,
		        m.status, m.created_at, s.session_alias, m.rename_alias, m.rename_reason
		 FROM mails m
		 JOIN sessions s ON m.session_id = s.session_id
		 WHERE m.mail_id = $1`, id,
	).Scan(&m.ID, &m.SessionID, &m.ParentMailID,
		&m.FromName, &m.FromWorkspace, &m.ToName, &m.ToWorkspace,
		&ccJSON, &m.Subject, &m.Body, &m.MailType, &m.PermResult,
		&m.Status, &m.CreatedAt, &alias, &renameAlias, &renameReason)
	if err != nil {
		return nil, err
	}
	if len(ccJSON) > 0 {
		json.Unmarshal(ccJSON, &m.CCList)
	}
	if m.CCList == nil {
		m.CCList = []models.Address{}
	}
	if alias != nil {
		m.SessionAlias = *alias
	}
	// 改名提议随单封返回，让「谁在哪一封里提了什么」可追溯；
	// 【待处理】的提议另有专用端点（GET /sessions/:id/rename-proposal）。
	if renameAlias != nil {
		m.RenameAlias = *renameAlias
	}
	if renameReason != nil {
		m.RenameReason = *renameReason
	}
	return &m, nil
}

func MarkMailRead(ctx context.Context, id uuid.UUID) error {
	_, err := db.DB.ExecContext(ctx, `UPDATE mails SET status = 'read' WHERE mail_id = $1`, id)
	return err
}

func ListInbox(ctx context.Context, agentName, status string, limit int) ([]models.Mail, error) {
	q := `SELECT m.mail_id, m.session_id, m.parent_mail_id,
	             m.from_name, m.from_workspace, m.to_name, m.to_workspace,
	             m.cc_list, m.subject, m.body, m.mail_type, COALESCE(m.permission_result,'') AS permission_result,
	             m.status, m.created_at, s.session_alias
	      FROM mails m
	      JOIN sessions s ON m.session_id = s.session_id
	      WHERE (m.to_name = $1 OR ` + db.CCHas("m.cc_list", 1) + `)
	        AND s.status <> 'archived'`
	args := []any{agentName}
	if status != "" && status != "all" {
		q += ` AND m.status = $2`
		args = append(args, status)
	}
	q += ` ORDER BY m.created_at DESC, m.mail_id DESC`
	if limit > 0 {
		q += fmt.Sprintf(` LIMIT %d`, limit)
	}

	rows, err := db.DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	mails := []models.Mail{}
	for rows.Next() {
		var m models.Mail
		var alias *string
		var ccJSON []byte
		if err := rows.Scan(&m.ID, &m.SessionID, &m.ParentMailID,
			&m.FromName, &m.FromWorkspace, &m.ToName, &m.ToWorkspace,
			&ccJSON, &m.Subject, &m.Body, &m.MailType, &m.PermResult,
			&m.Status, &m.CreatedAt, &alias); err != nil {
			return nil, err
		}
		if len(ccJSON) > 0 {
			json.Unmarshal(ccJSON, &m.CCList)
		}
		if m.CCList == nil {
			m.CCList = []models.Address{}
		}
		if alias != nil {
			m.SessionAlias = *alias
		}
		// Body preview
		if len(m.Body) > 200 {
			m.BodyPreview = m.Body[:200] + "..."
		} else {
			m.BodyPreview = m.Body
		}
		mails = append(mails, m)
	}
	return mails, rows.Err()
}

func CountUnread(ctx context.Context, agentName string) (int, error) {
	var count int
	err := db.DB.QueryRowContext(ctx, `
		SELECT COUNT(*)
		FROM mails m
		JOIN sessions s ON m.session_id = s.session_id
		WHERE (m.to_name = $1 OR `+db.CCHas("m.cc_list", 1)+`)
		  AND m.status = 'unread'
		  AND s.status <> 'archived'
	`, agentName).Scan(&count)
	return count, err
}

func GetSessionMails(ctx context.Context, sessionID uuid.UUID) ([]models.Mail, error) {
	rows, err := db.DB.QueryContext(ctx,
		`SELECT m.mail_id, m.session_id, m.parent_mail_id,
		        m.from_name, m.from_workspace, m.to_name, m.to_workspace,
		        m.cc_list, m.subject, m.body, m.mail_type, COALESCE(m.permission_result,'') AS permission_result,
		        m.status, m.created_at, s.session_alias
		 FROM mails m
		 JOIN sessions s ON m.session_id = s.session_id
		 WHERE m.session_id = $1
		 ORDER BY m.created_at ASC, m.mail_id ASC`, sessionID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	mails := []models.Mail{}
	for rows.Next() {
		var m models.Mail
		var alias *string
		var ccJSON []byte
		if err := rows.Scan(&m.ID, &m.SessionID, &m.ParentMailID,
			&m.FromName, &m.FromWorkspace, &m.ToName, &m.ToWorkspace,
			&ccJSON, &m.Subject, &m.Body, &m.MailType, &m.PermResult,
			&m.Status, &m.CreatedAt, &alias); err != nil {
			return nil, err
		}
		if len(ccJSON) > 0 {
			json.Unmarshal(ccJSON, &m.CCList)
		}
		if m.CCList == nil {
			m.CCList = []models.Address{}
		}
		if alias != nil {
			m.SessionAlias = *alias
		}
		mails = append(mails, m)
	}
	return mails, rows.Err()
}

// ---------- Permission ----------

func CreatePermissionRequest(ctx context.Context, mailID, sessionID uuid.UUID, agentName, question string, options []string, contextStr string) error {
	optsJSON, _ := json.Marshal(options)
	_, err := db.DB.ExecContext(ctx,
		`INSERT INTO permission_requests (mail_id, session_id, agent_name, question, options, context)
		 VALUES ($1, $2, $3, $4, $5, $6)`,
		mailID, sessionID, agentName, question, optsJSON, contextStr)
	return err
}

func DecidePermission(ctx context.Context, mailID uuid.UUID, decision string) (*models.PermissionRequest, error) {
	var pr models.PermissionRequest
	var optsJSON []byte

	err := db.DB.QueryRowContext(ctx,
		`UPDATE permission_requests SET result = $1, decided_at = NOW()
		 WHERE mail_id = $2
		 RETURNING request_id, mail_id, session_id, agent_name, question, options, context, result, decided_at, created_at`,
		decision, mailID,
	).Scan(&pr.ID, &pr.MailID, &pr.SessionID, &pr.AgentName, &pr.Question,
		&optsJSON, &pr.Context, &pr.Result, &pr.DecidedAt, &pr.CreatedAt)
	if err != nil {
		return nil, err
	}
	json.Unmarshal(optsJSON, &pr.Options)

	// Also update the mail
	_, _ = db.DB.ExecContext(context.Background(),
		`UPDATE mails SET permission_result = $1, status = 'read' WHERE mail_id = $2`,
		decision, mailID)

	return &pr, nil
}

func ListPendingPermissions(ctx context.Context) ([]models.PermissionRequest, error) {
	rows, err := db.DB.QueryContext(ctx,
		`SELECT request_id, mail_id, session_id, agent_name, question, options, context, result, decided_at, created_at
		 FROM permission_requests WHERE result IS NULL
		 ORDER BY created_at DESC`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	reqs := []models.PermissionRequest{}
	for rows.Next() {
		var pr models.PermissionRequest
		var optsJSON []byte
		if err := rows.Scan(&pr.ID, &pr.MailID, &pr.SessionID, &pr.AgentName, &pr.Question,
			&optsJSON, &pr.Context, &pr.Result, &pr.DecidedAt, &pr.CreatedAt); err != nil {
			return nil, err
		}
		json.Unmarshal(optsJSON, &pr.Options)
		reqs = append(reqs, pr)
	}
	return reqs, nil
}

// ---------- Check permission ownership ----------

func GetPermissionByMailID(ctx context.Context, mailID uuid.UUID) (*models.PermissionRequest, error) {
	var pr models.PermissionRequest
	var optsJSON []byte
	err := db.DB.QueryRowContext(ctx,
		`SELECT request_id, mail_id, session_id, agent_name, question, options, context, result, decided_at, created_at
		 FROM permission_requests WHERE mail_id = $1`, mailID,
	).Scan(&pr.ID, &pr.MailID, &pr.SessionID, &pr.AgentName, &pr.Question,
		&optsJSON, &pr.Context, &pr.Result, &pr.DecidedAt, &pr.CreatedAt)
	if err != nil {
		return nil, err
	}
	json.Unmarshal(optsJSON, &pr.Options)
	return &pr, nil
}

func GetSessionMailByID(ctx context.Context, sessionID, mailID uuid.UUID) (*models.Mail, error) {
	var m models.Mail
	var alias *string
	var ccJSON []byte
	err := db.DB.QueryRowContext(ctx,
		`SELECT m.mail_id, m.session_id, m.parent_mail_id,
		        m.from_name, m.from_workspace, m.to_name, m.to_workspace,
		        m.cc_list, m.subject, m.body, m.mail_type, COALESCE(m.permission_result,'') AS permission_result,
		        m.status, m.created_at, s.session_alias
		 FROM mails m JOIN sessions s ON m.session_id = s.session_id
		 WHERE m.session_id = $1 AND m.mail_id = $2`, sessionID, mailID,
	).Scan(&m.ID, &m.SessionID, &m.ParentMailID,
		&m.FromName, &m.FromWorkspace, &m.ToName, &m.ToWorkspace,
		&ccJSON, &m.Subject, &m.Body, &m.MailType, &m.PermResult,
		&m.Status, &m.CreatedAt, &alias)
	if err != nil {
		return nil, err
	}
	if len(ccJSON) > 0 {
		json.Unmarshal(ccJSON, &m.CCList)
	}
	if m.CCList == nil {
		m.CCList = []models.Address{}
	}
	if alias != nil {
		m.SessionAlias = *alias
	}
	return &m, nil
}

func FindSessionByAlias(ctx context.Context, alias string) (*models.Session, error) {
	var s models.Session
	err := db.DB.QueryRowContext(ctx,
		`SELECT session_id, session_alias, from_agent, subject, status, owner_user_id, created_at, updated_at
		 FROM sessions WHERE session_alias = $1 AND status <> 'archived'`, alias,
	).Scan(&s.ID, &s.Alias, &s.FromAgent, &s.Subject, &s.Status, &s.OwnerUserID, &s.CreatedAt, &s.UpdatedAt)
	if err != nil {
		return nil, err
	}
	return &s, nil
}

// ErrSessionNotFound 表示三维地址里指定的 session 别名不存在（或不属于该收件人）。
// 调用方应据此回 404「无法送达」，而不是悄悄新建一个会话。
var ErrSessionNotFound = errors.New("session not found")

// FindNamedSessionFor 查找收件人 name@path 名下别名为 alias 的会话。
// 严格匹配：会话必须存在、未归档，且该收件人确实参与过该会话，否则返回 ErrSessionNotFound。
func FindNamedSessionFor(ctx context.Context, name, path, alias string) (uuid.UUID, error) {
	var id uuid.UUID
	err := db.DB.QueryRowContext(ctx, `
		SELECT s.session_id
		FROM sessions s
		WHERE s.session_alias = $1
		  AND s.status <> 'archived'
		  AND EXISTS (
		      SELECT 1 FROM mails m
		      WHERE m.session_id = s.session_id
		        AND (m.to_name = $2 OR m.from_name = $2 OR `+db.CCHas("m.cc_list", 2)+`)
		  )
		ORDER BY s.updated_at DESC
		LIMIT 1
	`, alias, name).Scan(&id)
	if errors.Is(err, sql.ErrNoRows) {
		return uuid.Nil, ErrSessionNotFound
	}
	return id, err
}

// FindOrCreateDefaultSession 实现 session 位省略时的「默认会话」语义：
// 复用 name@path 最近一次活跃的非归档会话；从未通过信则建立一个新的作为默认会话。
func FindOrCreateDefaultSession(ctx context.Context, name, path, fromAgent, subject string) (uuid.UUID, error) {
	var id uuid.UUID
	err := db.DB.QueryRowContext(ctx, `
		SELECT s.session_id
		FROM sessions s
		JOIN mails m ON m.session_id = s.session_id
		WHERE s.status <> 'archived'
		  AND (m.to_name = $1 OR m.from_name = $1 OR `+db.CCHas("m.cc_list", 1)+`)
		  AND (COALESCE(m.to_workspace,'') = $2 OR COALESCE(m.from_workspace,'') = $2)
		ORDER BY s.updated_at DESC
		LIMIT 1
	`, name, path).Scan(&id)
	if err == nil {
		TouchSession(ctx, id)
		return id, nil
	}
	if !errors.Is(err, sql.ErrNoRows) {
		return uuid.Nil, err
	}
	return CreateSession(ctx, nil, fromAgent, subject)
}

// SessionAliasOf 返回会话别名，未命名或查询失败时返回空串。
// 仅用于响应体回显，不影响投递路径，所以吞错是可接受的。
func SessionAliasOf(ctx context.Context, id uuid.UUID) string {
	var alias *string
	if err := db.DB.QueryRowContext(ctx,
		`SELECT session_alias FROM sessions WHERE session_id = $1`, id).Scan(&alias); err != nil {
		return ""
	}
	if alias == nil {
		return ""
	}
	return *alias
}

// AgentCanAccessSession 判断 Agent 是否参与过该会话（发件/收件/被抄送）。
// Agent 只能改自己参与的会话的别名，避免跨会话改名。
func AgentCanAccessSession(ctx context.Context, agentName string, sessionID uuid.UUID) (bool, error) {
	var n int
	err := db.DB.QueryRowContext(ctx, `
		SELECT COUNT(*) FROM mails m
		WHERE m.session_id = $1
		  AND (m.from_name = $2 OR m.to_name = $2 OR `+db.CCHas("m.cc_list", 2)+`)
	`, sessionID, agentName).Scan(&n)
	return n > 0, err
}

// SyncSessionTitle 更新会话主题（Agent 平台生成的摘要标题）。
func SyncSessionTitle(ctx context.Context, id uuid.UUID, title string) error {
	_, err := db.DB.ExecContext(ctx,
		`UPDATE sessions SET subject = $1, updated_at = NOW() WHERE session_id = $2`,
		title, id)
	return err
}

// SyncSessionAlias 把 Agent 平台侧的会话标识写为本侧别名。
// 平台侧标识（如 opencode 的 slug）在平台内不保证全局唯一，而本侧别名负责寻址必须唯一，
// 因此撞名时自动追加 -2、-3… 后缀而不是报错——同步是后台行为，不该因撞名失败。
// 返回最终落库的别名。该会话已持有目标别名时直接返回，不做无谓写入。
//
// **人显式定过的别名不覆盖**（alias_source = 'manual'）：
// 用户刚接受了 Agent 的改名提议，或手工敲了一个名字，平台下一次 session.updated
// 不该把它冲掉 —— 那会让人上一秒记住的寻址地址下一秒失效。
// 此时返回当前别名，调用方据此知道同步未生效。
func SyncSessionAlias(ctx context.Context, id uuid.UUID, want string) (string, error) {
	const maxAttempts = 50

	var cur *string
	var source string
	if err := db.DB.QueryRowContext(ctx,
		`SELECT session_alias, COALESCE(alias_source, 'platform') FROM sessions WHERE session_id = $1`,
		id).Scan(&cur, &source); err != nil {
		return "", err
	}
	if source == "manual" && cur != nil && *cur != "" {
		return *cur, nil
	}

	for i := 0; i < maxAttempts; i++ {
		candidate := want
		if i > 0 {
			candidate = fmt.Sprintf("%s-%d", want, i+1)
		}

		owner, err := aliasOwner(ctx, candidate)
		if err != nil {
			return "", err
		}
		if owner != nil {
			if *owner == id {
				return candidate, nil // 已经是这个别名，无需写入
			}
			continue // 被别人占用，试下一个后缀
		}

		// 只在仍是 platform 来源时写入：并发下用户可能刚好接受了改名提议，
		// 条件放进 WHERE 才能保证「检查」与「写入」不被插进来的手工改名割开
		res, err := db.DB.ExecContext(ctx,
			`UPDATE sessions SET session_alias = $1, updated_at = NOW()
			 WHERE session_id = $2 AND COALESCE(alias_source, 'platform') <> 'manual'`,
			candidate, id)
		if err == nil {
			if n, _ := res.RowsAffected(); n == 0 {
				// 期间变成 manual 了，尊重人的选择
				return SessionAliasOf(ctx, id), nil
			}
			return candidate, nil
		}
		// 并发下另一个请求刚占走该别名（唯一索引拦下），继续试下一个后缀
		if db.IsUniqueViolation(err) {
			continue
		}
		return "", err
	}
	return "", fmt.Errorf("alias %q: 连同 -2..-%d 后缀均被占用", want, maxAttempts)
}

// aliasOwner 返回持有该别名的会话 ID；无人持有时返回 nil。
func aliasOwner(ctx context.Context, alias string) (*uuid.UUID, error) {
	var id uuid.UUID
	err := db.DB.QueryRowContext(ctx,
		`SELECT session_id FROM sessions WHERE session_alias = $1`, alias).Scan(&id)
	if errors.Is(err, sql.ErrNoRows) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	return &id, nil
}

func SessionMailCount(ctx context.Context, sessionID uuid.UUID) (int, error) {
	var count int
	err := db.DB.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM mails WHERE session_id = $1`, sessionID).Scan(&count)
	return count, err
}

// ---------- Contacts / Archive ----------

// Contact 是「联系人」= 一条 name@path.session 三维地址
type Contact struct {
	SessionID    uuid.UUID `json:"session_id"`
	AgentName    string    `json:"agent_name"`
	Path         string    `json:"path"`
	SessionAlias string    `json:"session_alias"`
	Address      string    `json:"address"` // name@path.session
	Status       string    `json:"status"`
	MailCount    int       `json:"mail_count"`
	UnreadCount  int       `json:"unread_count"`
	LastActivity time.Time `json:"last_activity"`

	// Subject 是会话主题（多由 Agent 平台的模型生成的摘要）。
	// 卡片视图要靠它回答「这条线索在干什么」—— 光有 name@path.alias
	// 只能看出跟谁在聊，看不出在聊什么。
	Subject string `json:"subject"`

	// MaxRounds/UsedRounds 是本任务的往返预算（0 = 不限）。
	// 列表上直接可见，才不用点进每条会话去查哪件事快跑满了。
	MaxRounds  int `json:"max_rounds"`
	UsedRounds int `json:"used_rounds"`

	// LastFrom/LastPreview 是最后一封邮件的发件人与正文摘要，
	// 卡片视图用它显示「最新进展」——列表视图只显示地址时，
	// 人必须逐条点开才知道哪条有新动静。
	LastFrom    string `json:"last_from"`
	LastPreview string `json:"last_preview"`
}

// ListContactsFor 按 (agent, path, session) 聚合出联系人清单。
// forUser 非空时只列该用户参与的会话（owner / 收发 / 抄送）；空表示不限（管理员全局视图）。
// archived=false 只列活跃会话，true 只列归档会话。
func ListContactsFor(ctx context.Context, forUser string, archived bool) ([]Contact, error) {
	op := "<>"
	if archived {
		op = "="
	}
	scope := ""
	args := []any{}
	if forUser != "" {
		scope = ` AND (s.owner_user_id = (SELECT user_id FROM users WHERE username = $1)
		              OR EXISTS (
		                  SELECT 1 FROM mails mm
		                  WHERE mm.session_id = s.session_id
		                    AND (mm.from_name = $1 OR mm.to_name = $1
		                         OR `+db.CCHas("mm.cc_list", 1)+`)
		              ))`
		args = append(args, forUser)
	}
	// 取会话里最早那封邮件作为联系人身份。
	// PG 用 LATERAL 子查询；SQLite 无 LATERAL，改用关联子查询逐列取值
	// （同一个 min(created_at) 子句，四列取自同一行）。
	var firstMail string
	if db.D == db.Postgres {
		firstMail = `
		JOIN LATERAL (
		    SELECT to_name, to_workspace, from_name, from_workspace
		    FROM mails
		    WHERE session_id = s.session_id
		    ORDER BY created_at ASC
		    LIMIT 1
		) m ON TRUE`
	} else {
		firstMail = `
		JOIN mails m ON m.mail_id = (
		    SELECT mail_id FROM mails
		    WHERE session_id = s.session_id
		    ORDER BY created_at ASC, mail_id ASC
		    LIMIT 1
		)`
	}

	// 最后一封邮件用关联子查询取，不再 JOIN 一次：
	// 两个 JOIN（最早一封 + 最新一封）在 SQLite 下要写两段方言分支，
	// 而这里每个会话只多两次索引查找（idx_mails_session 已有）。
	lastMail := `(
		    SELECT mail_id FROM mails
		    WHERE session_id = s.session_id
		    ORDER BY created_at DESC, mail_id DESC
		    LIMIT 1
		)`

	rows, err := db.DB.QueryContext(ctx, `
		SELECT s.session_id,
		       COALESCE(NULLIF(m.to_name, 'human'), m.from_name)      AS agent_name,
		       COALESCE(NULLIF(m.to_workspace, ''), m.from_workspace)  AS path,
		       COALESCE(s.session_alias, '')                          AS alias,
		       s.status,
		       (SELECT COUNT(*) FROM mails x WHERE x.session_id = s.session_id),
		       (SELECT COUNT(*) FROM mails x WHERE x.session_id = s.session_id AND x.status = 'unread'),
		       s.updated_at,
		       s.subject,
		       COALESCE(s.max_rounds, 0),
		       COALESCE(s.used_rounds, 0),
		       COALESCE((SELECT from_name FROM mails WHERE mail_id = `+lastMail+`), ''),
		       COALESCE((SELECT body      FROM mails WHERE mail_id = `+lastMail+`), '')
		FROM sessions s`+firstMail+`
		WHERE s.status `+op+` 'archived'`+scope+`
		ORDER BY s.updated_at DESC
	`, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	contacts := []Contact{}
	for rows.Next() {
		var c Contact
		if err := rows.Scan(&c.SessionID, &c.AgentName, &c.Path, &c.SessionAlias,
			&c.Status, &c.MailCount, &c.UnreadCount, &c.LastActivity,
			&c.Subject, &c.MaxRounds, &c.UsedRounds,
			&c.LastFrom, &c.LastPreview); err != nil {
			return nil, err
		}
		c.Address = c.AgentName + "@" + c.Path
		if c.SessionAlias != "" {
			c.Address += "." + c.SessionAlias
		}
		// 正文只留一段摘要：卡片上放不下全文，而整个列表带全文可能几百 KB。
		// 按 rune 截断而非字节 —— 中文 3 字节/字，裸切会产生 U+FFFD。
		c.LastPreview = previewRunes(c.LastPreview, 90)
		contacts = append(contacts, c)
	}
	return contacts, rows.Err()
}

// previewRunes 按字符数截断，附省略号。
// 不按字节切：中文一字三字节，裸切会在末尾留半个字符（渲染成 U+FFFD）。
func previewRunes(s string, n int) string {
	s = strings.TrimSpace(s)
	rs := []rune(s)
	if len(rs) <= n {
		return s
	}
	return string(rs[:n]) + "…"
}

// ArchiveSession 归档一个会话（邮箱界面不再展示，数据保留）
func ArchiveSession(ctx context.Context, sessionID uuid.UUID) error {
	_, err := db.DB.ExecContext(ctx,
		`UPDATE sessions SET status = 'archived', updated_at = NOW() WHERE session_id = $1`,
		sessionID)
	if err != nil {
		return err
	}
	// 同时把该会话下的邮件标记为已归档，收件箱不再列出
	_, err = db.DB.ExecContext(ctx,
		`UPDATE mails SET status = 'archived' WHERE session_id = $1 AND status <> 'archived'`,
		sessionID)
	return err
}

// FindSessionByAddress 按 name@path.session 定位会话
func FindSessionByAddress(ctx context.Context, name, path, alias string) (uuid.UUID, error) {
	var id uuid.UUID
	err := db.DB.QueryRowContext(ctx, `
		SELECT s.session_id
		FROM sessions s
		JOIN mails m ON m.session_id = s.session_id
		WHERE COALESCE(s.session_alias, '') = $1
		  AND (m.to_name = $2 OR m.from_name = $2)
		  AND (COALESCE(m.to_workspace,'') = $3 OR COALESCE(m.from_workspace,'') = $3)
		LIMIT 1
	`, alias, name, path).Scan(&id)
	return id, err
}

// SuggestPaths 返回某 agent 已注册的工作区名（用于发信补全）
func SuggestPaths(ctx context.Context, agentName string) ([]string, error) {
	var wsJSON []byte
	err := db.DB.QueryRowContext(ctx,
		`SELECT workspaces FROM agents WHERE agent_name = $1`, agentName).Scan(&wsJSON)
	if err != nil {
		return []string{}, err
	}
	var ws []models.Workspace
	if len(wsJSON) > 0 {
		json.Unmarshal(wsJSON, &ws)
	}
	out := make([]string, 0, len(ws))
	for _, w := range ws {
		out = append(out, w.Name)
	}
	return out, nil
}

// SuggestSessionsFor 返回某 (peer, path) 下当前用户可见的会话别名（用于发信补全）
func SuggestSessionsFor(ctx context.Context, forUser, peerName, path string) ([]string, error) {
	rows, err := db.DB.QueryContext(ctx, `
		SELECT DISTINCT s.session_alias
		FROM sessions s
		JOIN mails m ON m.session_id = s.session_id
		WHERE s.session_alias IS NOT NULL
		  AND s.status <> 'archived'
		  AND (m.to_name = $1 OR m.from_name = $1)
		  AND ($2 = '' OR COALESCE(m.to_workspace,'') = $2 OR COALESCE(m.from_workspace,'') = $2)
		  AND ($3 = '' OR s.owner_user_id = (SELECT user_id FROM users WHERE username = $3)
		       OR EXISTS (
		           SELECT 1 FROM mails mm
		           WHERE mm.session_id = s.session_id
		             AND (mm.from_name = $3 OR mm.to_name = $3
		                  OR `+db.CCHas("mm.cc_list", 3)+`)
		       ))
		ORDER BY s.session_alias
	`, peerName, path, forUser)
	if err != nil {
		return []string{}, err
	}
	defer rows.Close()

	out := []string{}
	for rows.Next() {
		var alias string
		if err := rows.Scan(&alias); err == nil && alias != "" {
			out = append(out, alias)
		}
	}
	return out, rows.Err()
}

// ListSentBy 列出某发件人发出的邮件（发件箱），排除已归档会话
func ListSentBy(ctx context.Context, fromName string, limit int) ([]models.Mail, error) {
	rows, err := db.DB.QueryContext(ctx, `
		SELECT m.mail_id, m.session_id, m.parent_mail_id,
		       m.from_name, m.from_workspace, m.to_name, m.to_workspace,
		       m.cc_list, m.subject, m.body, m.mail_type, COALESCE(m.permission_result,'') AS permission_result,
		       m.status, m.created_at, s.session_alias
		FROM mails m
		JOIN sessions s ON m.session_id = s.session_id
		WHERE m.from_name = $1 AND s.status <> 'archived'
		ORDER BY m.created_at DESC, m.mail_id DESC
		LIMIT $2
	`, fromName, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	mails := []models.Mail{}
	for rows.Next() {
		var m models.Mail
		var alias *string
		var ccJSON []byte
		if err := rows.Scan(&m.ID, &m.SessionID, &m.ParentMailID,
			&m.FromName, &m.FromWorkspace, &m.ToName, &m.ToWorkspace,
			&ccJSON, &m.Subject, &m.Body, &m.MailType, &m.PermResult,
			&m.Status, &m.CreatedAt, &alias); err != nil {
			return nil, err
		}
		if len(ccJSON) > 0 {
			json.Unmarshal(ccJSON, &m.CCList)
		}
		if m.CCList == nil {
			m.CCList = []models.Address{}
		}
		if alias != nil {
			m.SessionAlias = *alias
		}
		if len(m.Body) > 200 {
			m.BodyPreview = m.Body[:200] + "..."
		} else {
			m.BodyPreview = m.Body
		}
		mails = append(mails, m)
	}
	return mails, rows.Err()
}

// ListPendingPermissionsFor 列出待决权限请求；forUser 非空时只列发给该用户的
func ListPendingPermissionsFor(ctx context.Context, forUser string) ([]models.PermissionRequest, error) {
	q := `SELECT pr.request_id, pr.mail_id, pr.session_id, pr.agent_name, pr.question,
	             pr.options, pr.context, pr.result, pr.decided_at, pr.created_at
	      FROM permission_requests pr
	      JOIN mails m ON m.mail_id = pr.mail_id
	      JOIN sessions s ON s.session_id = pr.session_id
	      WHERE pr.result IS NULL AND s.status <> 'archived'`
	args := []any{}
	if forUser != "" {
		q += ` AND m.to_name = $1`
		args = append(args, forUser)
	}
	q += ` ORDER BY pr.created_at DESC`

	rows, err := db.DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	reqs := []models.PermissionRequest{}
	for rows.Next() {
		var pr models.PermissionRequest
		var optsJSON []byte
		if err := rows.Scan(&pr.ID, &pr.MailID, &pr.SessionID, &pr.AgentName, &pr.Question,
			&optsJSON, &pr.Context, &pr.Result, &pr.DecidedAt, &pr.CreatedAt); err != nil {
			return nil, err
		}
		json.Unmarshal(optsJSON, &pr.Options)
		reqs = append(reqs, pr)
	}
	return reqs, nil
}

// ListSessionsFor 列出某人类用户参与的会话（owner / 收发 / 抄送）；forUser 空表示不限
func ListSessionsFor(ctx context.Context, forUser string, limit int) ([]models.Session, error) {
	q := `SELECT s.session_id, s.session_alias, s.from_agent, s.subject, s.status,
	             s.owner_user_id, s.created_at, s.updated_at,
	             COALESCE(s.max_rounds, 0), COALESCE(s.used_rounds, 0),
	             (SELECT COUNT(*) FROM mails m WHERE m.session_id = s.session_id)
	      FROM sessions s
	      WHERE s.status <> 'archived'`
	args := []any{}
	if forUser != "" {
		q += ` AND (s.owner_user_id = (SELECT user_id FROM users WHERE username = $1)
		            OR EXISTS (
		                SELECT 1 FROM mails mm
		                WHERE mm.session_id = s.session_id
		                  AND (mm.from_name = $1 OR mm.to_name = $1
		                       OR `+db.CCHas("mm.cc_list", 1)+`)
		            ))`
		args = append(args, forUser)
	}
	q += ` ORDER BY s.updated_at DESC`
	if limit > 0 {
		q += fmt.Sprintf(` LIMIT %d`, limit)
	}

	rows, err := db.DB.QueryContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	sessions := []models.Session{}
	for rows.Next() {
		var s models.Session
		// 列数必须与上面的 SELECT 一一对应 —— 预算两列曾经只加进了查询而没加进这里，
		// 结果 /me/sessions 整个 500，联系人栅拉不到任何数据。
		if err := rows.Scan(&s.ID, &s.Alias, &s.FromAgent, &s.Subject, &s.Status,
			&s.OwnerUserID, &s.CreatedAt, &s.UpdatedAt,
			&s.MaxRounds, &s.UsedRounds, &s.MailCount); err != nil {
			return nil, err
		}
		sessions = append(sessions, s)
	}
	return sessions, rows.Err()
}

// CountUnreadInSession 统计某人在某会话内的未读数（含被抄送）
func CountUnreadInSession(ctx context.Context, name string, sessionID uuid.UUID) (int, error) {
	ccProbe, _ := json.Marshal([]map[string]string{{"name": name}})
	var n int
	err := db.DB.QueryRowContext(ctx, `
		SELECT COUNT(*) FROM mails
		WHERE session_id = $1
		  AND status = 'unread'
		  AND (to_name = $2 OR cc_list @> $3::jsonb)
	`, sessionID, name, string(ccProbe)).Scan(&n)
	return n, err
}

// SetMailRenameProposal 记录某封邮件里 Agent 提议的新会话别名。
//
// 单独一条 UPDATE 而不是塞进 CreateMail 的参数表：提议是可选的旁支信息，
// 让三个调用点都多传两个几乎总是空串的参数不值当。
func SetMailRenameProposal(ctx context.Context, mailID uuid.UUID, alias, reason string) error {
	_, err := db.DB.ExecContext(ctx,
		`UPDATE mails SET rename_alias = $1, rename_reason = $2 WHERE mail_id = $3`,
		alias, reason, mailID)
	return err
}

// PendingRenameProposal 返回某会话里**最新一条尚未处理**的改名提议。
//
// 「尚未处理」= 提议的别名既不是当前别名（已接受），也不在驳回记录里。
// 无提议时返回 ("", "", nil)。
//
// 只看最新一条：Agent 干活过程中可能多次提议，最后那条才是它现在的结论。
func PendingRenameProposal(ctx context.Context, sessionID uuid.UUID) (alias, reason string, err error) {
	var cur, dismissed *string
	err = db.DB.QueryRowContext(ctx,
		`SELECT session_alias, rename_dismissed FROM sessions WHERE session_id = $1`,
		sessionID).Scan(&cur, &dismissed)
	if err != nil {
		return "", "", err
	}

	var a, rs *string
	err = db.DB.QueryRowContext(ctx, `
		SELECT rename_alias, rename_reason FROM mails
		WHERE session_id = $1 AND rename_alias IS NOT NULL AND rename_alias <> ''
		ORDER BY created_at DESC, mail_id DESC
		LIMIT 1
	`, sessionID).Scan(&a, &rs)
	if errors.Is(err, sql.ErrNoRows) {
		return "", "", nil
	}
	if err != nil {
		return "", "", err
	}
	if a == nil || *a == "" {
		return "", "", nil
	}
	// 已经改成这个名字了 = 提议已被接受，不必再提示
	if cur != nil && *cur == *a {
		return "", "", nil
	}
	// 用户驳回过这个建议
	if dismissed != nil && *dismissed == *a {
		return "", "", nil
	}
	if rs != nil {
		reason = *rs
	}
	return *a, reason, nil
}

// DismissRenameProposal 记下用户驳回了哪个建议，好让提示条不再反复弹。
//
// 只存最后驳回的那一个而不是一张列表：Agent 每次提的名字都不同，
// 攒一张历史表除了占地方没有别的用处 —— 需要判断的只是「当前这条提议是否被否过」。
func DismissRenameProposal(ctx context.Context, sessionID uuid.UUID, alias string) error {
	_, err := db.DB.ExecContext(ctx,
		`UPDATE sessions SET rename_dismissed = $1 WHERE session_id = $2`,
		alias, sessionID)
	return err
}

// MarkMailsReadFor 把一批邮件标记为某收件人已读，返回实际影响的行数。
//
// **鉴权写进 WHERE 而不是先查后改**：`to_name = $1 OR cc 含 $1` 直接放在
// UPDATE 条件里，于是「不是发给我的邮件」根本改不动 —— 既省掉一次查询，
// 也没有「查完到改之间邮件被转走」的时间窗。
//
// 已经是 read 的不计入影响行数（`status = 'unread'` 条件），
// 调用方据此知道这次真正标掉了几封。
func MarkMailsReadFor(ctx context.Context, recipient string, ids []uuid.UUID) (int, error) {
	if len(ids) == 0 {
		return 0, nil
	}

	// IN 子句的占位符按方言编号（SQLite 与 PG 都认 $N）。
	// 不用一条条 UPDATE：一次网络往返 + 一次事务，SQLite 单写者下差别明显。
	ph := make([]string, len(ids))
	args := make([]any, 0, len(ids)+1)
	args = append(args, recipient)
	for i, id := range ids {
		ph[i] = fmt.Sprintf("$%d", i+2)
		args = append(args, id)
	}

	res, err := db.DB.ExecContext(ctx, `
		UPDATE mails SET status = 'read'
		WHERE mail_id IN (`+strings.Join(ph, ",")+`)
		  AND status = 'unread'
		  AND (to_name = $1 OR `+db.CCHas("cc_list", 1)+`)
	`, args...)
	if err != nil {
		return 0, err
	}
	n, _ := res.RowsAffected()
	return int(n), nil
}

// MarkAllInboxReadFor 把某收件人收件箱里全部未读标为已读，返回影响行数。
//
// 排除已归档会话：那些邮件在收件箱里根本看不到，
// 标掉它们只会让「标记了 N 封」这个数字与用户看到的对不上。
func MarkAllInboxReadFor(ctx context.Context, recipient string) (int, error) {
	res, err := db.DB.ExecContext(ctx, `
		UPDATE mails SET status = 'read'
		WHERE status = 'unread'
		  AND (to_name = $1 OR `+db.CCHas("cc_list", 1)+`)
		  AND session_id IN (SELECT session_id FROM sessions WHERE status <> 'archived')
	`, recipient)
	if err != nil {
		return 0, err
	}
	n, _ := res.RowsAffected()
	return int(n), nil
}