package docgov

import (
	"fmt"
	"strings"
	"time"
)

// StateMachine 文档编制/审核/批准生命周期状态机与权限守卫
type StateMachine struct{}

func NewStateMachine() *StateMachine {
	return &StateMachine{}
}

// CanEditDocumentContent 权限守卫 1：校验当前操作人是否有权修改文档正文
// 规则：
// 1. 文档处于锁定状态 (reviewing, approving, approved) 时严禁直接修改
// 2. 只有编制负责人 (Author) 有权修改文档正文；审核人和批准人严禁直接修改
func (sm *StateMachine) CanEditDocumentContent(doc *DocumentRecord, actorID int64, actorRole UserRole) error {
	if doc == nil {
		return ErrDocumentNotFound
	}

	// 1. 检查锁定状态
	if doc.IsLocked {
		return fmt.Errorf("%w: 当前文档处于【%s】状态并已锁定", ErrDocumentLocked, doc.CurrentState)
	}

	// 2. 状态合法性
	if doc.CurrentState != StateDrafting {
		return fmt.Errorf("%w: 只有在编制草稿状态 (drafting) 下才允许修改内容，当前为【%s】", ErrInvalidStateTransition, doc.CurrentState)
	}

	// 3. 角色与身份权限校验
	switch actorRole {
	case RoleReviewer:
		return ErrReviewerCannotEdit
	case RoleApprover:
		return ErrApproverCannotEdit
	case RoleAuthor:
		if doc.AuthorID > 0 && actorID > 0 && doc.AuthorID != actorID {
			return fmt.Errorf("%w: 文档编制负责人为用户ID %d，非操作人 %d", ErrOnlyAuthorCanEdit, doc.AuthorID, actorID)
		}
		return nil
	case RoleSystem:
		// 系统或智能体代为编辑：在编制中且未锁定阶段放行 (认领检查在外部业务层联动)
		return nil
	default:
		return ErrUnauthorizedActor
	}
}

// TransitionSubmitForReview 编制完成送审: drafting -> reviewing
// 只有编制负责人可以发起送审
func (sm *StateMachine) TransitionSubmitForReview(doc *DocumentRecord, actorID int64, actorRole UserRole, actorName string) (*AuditLog, error) {
	if doc == nil {
		return nil, ErrDocumentNotFound
	}
	if doc.CurrentState != StateDrafting {
		return nil, fmt.Errorf("%w: 无法从【%s】阶段提交审核，必须为【drafting】", ErrInvalidStateTransition, doc.CurrentState)
	}
	if actorRole != RoleAuthor && actorRole != RoleSystem {
		return nil, fmt.Errorf("%w: 只有编制人或系统小队有权发起送审", ErrUnauthorizedActor)
	}
	if actorRole == RoleAuthor && doc.AuthorID > 0 && actorID > 0 && doc.AuthorID != actorID {
		return nil, fmt.Errorf("%w: 当前送审操作人 %d 不是该文档指定的编制人 %d", ErrUnauthorizedActor, actorID, doc.AuthorID)
	}

	fromState := doc.CurrentState
	toState := StateReviewing

	doc.CurrentState = toState
	doc.IsLocked = true // 审核阶段进入锁定状态
	now := time.Now()
	doc.UpdatedAt = now

	return &AuditLog{
		DocID:     doc.DocID,
		Action:    "submit_review",
		ActorID:   actorID,
		ActorName: actorName,
		ActorRole: actorRole,
		FromState: fromState,
		ToState:   toState,
		Details:   map[string]any{"timestamp": now},
		CreatedAt: now,
	}, nil
}

// TransitionReviewApprove 审核通过: reviewing -> approving
// 只有审核人有权执行
func (sm *StateMachine) TransitionReviewApprove(doc *DocumentRecord, actorID int64, actorRole UserRole, actorName string, comment string) (*AuditLog, error) {
	if doc == nil {
		return nil, ErrDocumentNotFound
	}
	if doc.CurrentState != StateReviewing {
		return nil, fmt.Errorf("%w: 无法在【%s】状态下执行审核通过，当前应为【reviewing】", ErrInvalidStateTransition, doc.CurrentState)
	}
	if actorRole != RoleReviewer && actorRole != RoleSystem {
		return nil, fmt.Errorf("%w: 只有审核人有权执行审核通过", ErrUnauthorizedActor)
	}
	if actorRole == RoleReviewer && doc.ReviewerID > 0 && actorID > 0 && doc.ReviewerID != actorID {
		return nil, fmt.Errorf("%w: 当前审核人 %d 与文档指定审核人 %d 不匹配", ErrUnauthorizedActor, actorID, doc.ReviewerID)
	}

	fromState := doc.CurrentState
	toState := StateApproving

	doc.CurrentState = toState
	doc.IsLocked = true // 批准阶段保持锁定
	now := time.Now()
	doc.UpdatedAt = now

	return &AuditLog{
		DocID:     doc.DocID,
		Action:    "review_approve",
		ActorID:   actorID,
		ActorName: actorName,
		ActorRole: actorRole,
		FromState: fromState,
		ToState:   toState,
		Details:   map[string]any{"comment": comment, "timestamp": now},
		CreatedAt: now,
	}, nil
}

// TransitionReviewReject 审核驳回: reviewing -> drafting
// 审核人驳回时必须填写驳回原因，退回编制草稿并解锁，记录驳回上下文
func (sm *StateMachine) TransitionReviewReject(doc *DocumentRecord, actorID int64, actorRole UserRole, actorName string, rejectReason string) (*AuditLog, error) {
	if doc == nil {
		return nil, ErrDocumentNotFound
	}
	if doc.CurrentState != StateReviewing {
		return nil, fmt.Errorf("%w: 无法在【%s】状态下执行审核驳回，当前应为【reviewing】", ErrInvalidStateTransition, doc.CurrentState)
	}
	if actorRole != RoleReviewer && actorRole != RoleSystem {
		return nil, fmt.Errorf("%w: 只有审核人有权执行审核驳回", ErrUnauthorizedActor)
	}
	if actorRole == RoleReviewer && doc.ReviewerID > 0 && actorID > 0 && doc.ReviewerID != actorID {
		return nil, fmt.Errorf("%w: 当前审核人 %d 与文档指定审核人 %d 不匹配", ErrUnauthorizedActor, actorID, doc.ReviewerID)
	}

	trimmedReason := strings.TrimSpace(rejectReason)
	if trimmedReason == "" {
		return nil, ErrRejectReasonRequired
	}

	fromState := doc.CurrentState
	toState := StateDrafting

	doc.CurrentState = toState
	doc.IsLocked = false // 退回编制草稿阶段，解锁文档供编制人修订
	now := time.Now()
	doc.LastRejectedReason = trimmedReason
	doc.LastRejectedByRole = string(actorRole)
	doc.LastRejectedByName = actorName
	doc.LastRejectedAt = &now
	doc.UpdatedAt = now

	return &AuditLog{
		DocID:     doc.DocID,
		Action:    "review_reject",
		ActorID:   actorID,
		ActorName: actorName,
		ActorRole: actorRole,
		FromState: fromState,
		ToState:   toState,
		Details: map[string]any{
			"reject_reason": trimmedReason,
			"timestamp":     now,
		},
		CreatedAt: now,
	}, nil
}

// TransitionApproverApprove 批准通过: approving -> approved (终态归档)
func (sm *StateMachine) TransitionApproverApprove(doc *DocumentRecord, actorID int64, actorRole UserRole, actorName string, comment string) (*AuditLog, error) {
	if doc == nil {
		return nil, ErrDocumentNotFound
	}
	if doc.CurrentState != StateApproving {
		return nil, fmt.Errorf("%w: 无法在【%s】状态下执行批准通过，当前应为【approving】", ErrInvalidStateTransition, doc.CurrentState)
	}
	if actorRole != RoleApprover && actorRole != RoleSystem {
		return nil, fmt.Errorf("%w: 只有批准人有权执行最终批准", ErrUnauthorizedActor)
	}
	if actorRole == RoleApprover && doc.ApproverID > 0 && actorID > 0 && doc.ApproverID != actorID {
		return nil, fmt.Errorf("%w: 当前批准人 %d 与文档指定批准人 %d 不匹配", ErrUnauthorizedActor, actorID, doc.ApproverID)
	}

	fromState := doc.CurrentState
	toState := StateApproved

	doc.CurrentState = toState
	doc.IsLocked = true // 终态受控归档锁定
	now := time.Now()
	doc.ApprovedAt = &now
	doc.UpdatedAt = now

	return &AuditLog{
		DocID:     doc.DocID,
		Action:    "approver_approve",
		ActorID:   actorID,
		ActorName: actorName,
		ActorRole: actorRole,
		FromState: fromState,
		ToState:   toState,
		Details: map[string]any{
			"comment":   comment,
			"timestamp": now,
		},
		CreatedAt: now,
	}, nil
}

// TransitionApproverReject 批准驳回: approving -> drafting 或 reviewing
// 驳回时必须填写驳回原因，退回目标根据配置和参数决定
func (sm *StateMachine) TransitionApproverReject(doc *DocumentRecord, actorID int64, actorRole UserRole, actorName string, rejectReason string, rollbackTo DocumentState) (*AuditLog, error) {
	if doc == nil {
		return nil, ErrDocumentNotFound
	}
	if doc.CurrentState != StateApproving {
		return nil, fmt.Errorf("%w: 无法在【%s】状态下执行批准驳回，当前应为【approving】", ErrInvalidStateTransition, doc.CurrentState)
	}
	if actorRole != RoleApprover && actorRole != RoleSystem {
		return nil, fmt.Errorf("%w: 只有批准人有权执行批准驳回", ErrUnauthorizedActor)
	}
	if actorRole == RoleApprover && doc.ApproverID > 0 && actorID > 0 && doc.ApproverID != actorID {
		return nil, fmt.Errorf("%w: 当前批准人 %d 与文档指定批准人 %d 不匹配", ErrUnauthorizedActor, actorID, doc.ApproverID)
	}

	trimmedReason := strings.TrimSpace(rejectReason)
	if trimmedReason == "" {
		return nil, ErrRejectReasonRequired
	}

	// 确定退回目标阶段
	targetState := rollbackTo
	if targetState == "" {
		targetState = doc.Config.RejectRollbackTo
	}
	if targetState != StateDrafting && targetState != StateReviewing {
		targetState = StateDrafting
	}
	if targetState == StateReviewing && !doc.Config.AllowApproverToReviewer {
		targetState = StateDrafting
	}

	fromState := doc.CurrentState
	toState := targetState

	doc.CurrentState = toState
	if toState == StateDrafting {
		doc.IsLocked = false // 退回编制阶段解锁
	} else {
		doc.IsLocked = true // 退回审核阶段保持锁定
	}

	now := time.Now()
	doc.LastRejectedReason = trimmedReason
	doc.LastRejectedByRole = string(actorRole)
	doc.LastRejectedByName = actorName
	doc.LastRejectedAt = &now
	doc.UpdatedAt = now

	return &AuditLog{
		DocID:     doc.DocID,
		Action:    "approver_reject",
		ActorID:   actorID,
		ActorName: actorName,
		ActorRole: actorRole,
		FromState: fromState,
		ToState:   toState,
		Details: map[string]any{
			"reject_reason": trimmedReason,
			"rollback_to":   toState,
			"timestamp":     now,
		},
		CreatedAt: now,
	}, nil
}