package sysadmin

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"

	"github.com/jackc/pgx/v5"
)

// SettingKeyAllowAuthorOnlyApproval 系统级「允许编制人兼任审核、批准」总授权。
// 默认关闭；无环境变量绕过；仅系统管理员可写。
const SettingKeyAllowAuthorOnlyApproval = "workflow.allow_author_only_approval"

// AuthorOnlyApprovalPolicy 供 projectinstance 消费的窄策略快照。
type AuthorOnlyApprovalPolicy struct {
	Key      string `json:"key"`
	Allowed  bool   `json:"allowed"`
	Revision int64  `json:"revision"`
}

// AuthorOnlyPolicySource 组合根注入给 projectinstance 的只读/事务锁接口。
// sysadmin 是唯一写入 owner；调用方不得自行写 system_settings。
type AuthorOnlyPolicySource interface {
	GetAuthorOnlyApprovalPolicy(ctx context.Context) (AuthorOnlyApprovalPolicy, error)
	LockAuthorOnlyApprovalPolicy(ctx context.Context, tx pgx.Tx) (AuthorOnlyApprovalPolicy, error)
}

// GetAuthorOnlyApprovalPolicy 读取当前总授权。缺行按默认关闭（revision=0）；
// 存储不可用或查询失败返回错误，不得伪装成默认关闭。
func (s *Service) GetAuthorOnlyApprovalPolicy(ctx context.Context) (AuthorOnlyApprovalPolicy, error) {
	out := AuthorOnlyApprovalPolicy{
		Key:      SettingKeyAllowAuthorOnlyApproval,
		Allowed:  false,
		Revision: 0,
	}
	if s.store == nil {
		return out, ErrStoreUnavailable
	}
	raw, _, _, revision, err := s.store.Get(ctx, SettingKeyAllowAuthorOnlyApproval)
	if err != nil {
		if errors.Is(err, ErrSettingNotFound) {
			return out, nil
		}
		return out, err
	}
	allowed, err := decodeStrictBool(raw)
	if err != nil {
		return out, fmt.Errorf("sysadmin: decode %s: %w", SettingKeyAllowAuthorOnlyApproval, err)
	}
	out.Allowed = allowed
	out.Revision = revision
	return out, nil
}

// LockAuthorOnlyApprovalPolicy 在调用方事务内锁定策略行，供激活与关闭串行化。
func (s *Service) LockAuthorOnlyApprovalPolicy(ctx context.Context, tx pgx.Tx) (AuthorOnlyApprovalPolicy, error) {
	out := AuthorOnlyApprovalPolicy{
		Key:      SettingKeyAllowAuthorOnlyApproval,
		Allowed:  false,
		Revision: 0,
	}
	if s.store == nil {
		return out, ErrStoreUnavailable
	}
	raw, _, _, revision, err := s.store.GetForUpdate(ctx, tx, SettingKeyAllowAuthorOnlyApproval)
	if err != nil {
		if errors.Is(err, ErrSettingNotFound) {
			// 迁移应已种子化；缺行按关闭处理但不伪装 DB 故障。
			return out, nil
		}
		return out, err
	}
	allowed, err := decodeStrictBool(raw)
	if err != nil {
		return out, fmt.Errorf("sysadmin: decode %s: %w", SettingKeyAllowAuthorOnlyApproval, err)
	}
	out.Allowed = allowed
	out.Revision = revision
	return out, nil
}

func decodeStrictBool(raw json.RawMessage) (bool, error) {
	if len(raw) == 0 {
		return false, ErrInvalidSettingValue
	}
	var v bool
	if err := json.Unmarshal(raw, &v); err != nil {
		return false, ErrInvalidSettingValue
	}
	return v, nil
}

// Ensure AuthorOnlyPolicySource 由 Service 实现。
var _ AuthorOnlyPolicySource = (*Service)(nil)