use chrono::Utc;
use sea_orm::{
    ActiveModelTrait, ColumnTrait, EntityTrait, PaginatorTrait, QueryFilter, Set,
};
use uuid::Uuid;

use crate::dto::{
    CreateProcessDefinitionReq, ProcessDefinitionResp, UpdateProcessDefinitionReq,
};
use crate::engine::parser;
use crate::entity::process_definition;
use crate::error::{WorkflowError, WorkflowResult};
use erp_core::events::EventBus;
use erp_core::types::Pagination;

/// 流程定义 CRUD 服务。
pub struct DefinitionService;

impl DefinitionService {
    /// 分页查询流程定义列表。
    pub async fn list(
        tenant_id: Uuid,
        pagination: &Pagination,
        db: &sea_orm::DatabaseConnection,
    ) -> WorkflowResult<(Vec<ProcessDefinitionResp>, u64)> {
        let paginator = process_definition::Entity::find()
            .filter(process_definition::Column::TenantId.eq(tenant_id))
            .filter(process_definition::Column::DeletedAt.is_null())
            .paginate(db, pagination.limit());

        let total = paginator
            .num_items()
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;

        let page_index = pagination.page.unwrap_or(1).saturating_sub(1) as u64;
        let models = paginator
            .fetch_page(page_index)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;

        let resps: Vec<ProcessDefinitionResp> = models.iter().map(Self::model_to_resp).collect();
        Ok((resps, total))
    }

    /// 获取单个流程定义。
    pub async fn get_by_id(
        id: Uuid,
        tenant_id: Uuid,
        db: &sea_orm::DatabaseConnection,
    ) -> WorkflowResult<ProcessDefinitionResp> {
        let model = process_definition::Entity::find_by_id(id)
            .one(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?
            .filter(|m| m.tenant_id == tenant_id && m.deleted_at.is_none())
            .ok_or_else(|| WorkflowError::NotFound(format!("流程定义不存在: {id}")))?;

        Ok(Self::model_to_resp(&model))
    }

    /// 创建流程定义。
    pub async fn create(
        tenant_id: Uuid,
        operator_id: Uuid,
        req: &CreateProcessDefinitionReq,
        db: &sea_orm::DatabaseConnection,
        event_bus: &EventBus,
    ) -> WorkflowResult<ProcessDefinitionResp> {
        // 验证流程图合法性
        parser::parse_and_validate(&req.nodes, &req.edges)?;

        let now = Utc::now();
        let id = Uuid::now_v7();
        let nodes_json = serde_json::to_value(&req.nodes)
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;
        let edges_json = serde_json::to_value(&req.edges)
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;

        let model = process_definition::ActiveModel {
            id: Set(id),
            tenant_id: Set(tenant_id),
            name: Set(req.name.clone()),
            key: Set(req.key.clone()),
            version: Set(1),
            category: Set(req.category.clone()),
            description: Set(req.description.clone()),
            nodes: Set(nodes_json),
            edges: Set(edges_json),
            status: Set("draft".to_string()),
            created_at: Set(now),
            updated_at: Set(now),
            created_by: Set(operator_id),
            updated_by: Set(operator_id),
            deleted_at: Set(None),
        };
        model
            .insert(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;

        event_bus.publish(erp_core::events::DomainEvent::new(
            "process_definition.created",
            tenant_id,
            serde_json::json!({ "definition_id": id, "key": req.key }),
        ));

        Ok(ProcessDefinitionResp {
            id,
            name: req.name.clone(),
            key: req.key.clone(),
            version: 1,
            category: req.category.clone(),
            description: req.description.clone(),
            nodes: serde_json::to_value(&req.nodes).unwrap_or_default(),
            edges: serde_json::to_value(&req.edges).unwrap_or_default(),
            status: "draft".to_string(),
            created_at: now,
            updated_at: now,
        })
    }

    /// 更新流程定义（仅 draft 状态可编辑）。
    pub async fn update(
        id: Uuid,
        tenant_id: Uuid,
        operator_id: Uuid,
        req: &UpdateProcessDefinitionReq,
        db: &sea_orm::DatabaseConnection,
    ) -> WorkflowResult<ProcessDefinitionResp> {
        let model = process_definition::Entity::find_by_id(id)
            .one(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?
            .filter(|m| m.tenant_id == tenant_id && m.deleted_at.is_none())
            .ok_or_else(|| WorkflowError::NotFound(format!("流程定义不存在: {id}")))?;

        if model.status != "draft" {
            return Err(WorkflowError::InvalidState(
                "只有 draft 状态的流程定义可以编辑".to_string(),
            ));
        }

        let mut active: process_definition::ActiveModel = model.into();

        if let Some(name) = &req.name {
            active.name = Set(name.clone());
        }
        if let Some(category) = &req.category {
            active.category = Set(Some(category.clone()));
        }
        if let Some(description) = &req.description {
            active.description = Set(Some(description.clone()));
        }
        if let Some(nodes) = &req.nodes {
            // 验证新流程图
            if let Some(edges) = &req.edges {
                parser::parse_and_validate(nodes, edges)?;
            }
            let nodes_json = serde_json::to_value(nodes)
                .map_err(|e| WorkflowError::Validation(e.to_string()))?;
            active.nodes = Set(nodes_json);
        }
        if let Some(edges) = &req.edges {
            let edges_json = serde_json::to_value(edges)
                .map_err(|e| WorkflowError::Validation(e.to_string()))?;
            active.edges = Set(edges_json);
        }

        active.updated_at = Set(Utc::now());
        active.updated_by = Set(operator_id);

        let updated = active
            .update(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;

        Ok(Self::model_to_resp(&updated))
    }

    /// 发布流程定义（draft → published）。
    pub async fn publish(
        id: Uuid,
        tenant_id: Uuid,
        operator_id: Uuid,
        db: &sea_orm::DatabaseConnection,
        event_bus: &EventBus,
    ) -> WorkflowResult<ProcessDefinitionResp> {
        let model = process_definition::Entity::find_by_id(id)
            .one(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?
            .filter(|m| m.tenant_id == tenant_id && m.deleted_at.is_none())
            .ok_or_else(|| WorkflowError::NotFound(format!("流程定义不存在: {id}")))?;

        if model.status != "draft" {
            return Err(WorkflowError::InvalidState(
                "只有 draft 状态的流程定义可以发布".to_string(),
            ));
        }

        // 验证流程图
        let nodes: Vec<crate::dto::NodeDef> = serde_json::from_value(model.nodes.clone())
            .map_err(|e| WorkflowError::InvalidDiagram(format!("节点数据无效: {e}")))?;
        let edges: Vec<crate::dto::EdgeDef> = serde_json::from_value(model.edges.clone())
            .map_err(|e| WorkflowError::InvalidDiagram(format!("连线数据无效: {e}")))?;
        parser::parse_and_validate(&nodes, &edges)?;

        let mut active: process_definition::ActiveModel = model.into();
        active.status = Set("published".to_string());
        active.updated_at = Set(Utc::now());
        active.updated_by = Set(operator_id);

        let updated = active
            .update(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;

        event_bus.publish(erp_core::events::DomainEvent::new(
            "process_definition.published",
            tenant_id,
            serde_json::json!({ "definition_id": id }),
        ));

        Ok(Self::model_to_resp(&updated))
    }

    /// 软删除流程定义。
    pub async fn delete(
        id: Uuid,
        tenant_id: Uuid,
        operator_id: Uuid,
        db: &sea_orm::DatabaseConnection,
    ) -> WorkflowResult<()> {
        let model = process_definition::Entity::find_by_id(id)
            .one(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?
            .filter(|m| m.tenant_id == tenant_id && m.deleted_at.is_none())
            .ok_or_else(|| WorkflowError::NotFound(format!("流程定义不存在: {id}")))?;

        let mut active: process_definition::ActiveModel = model.into();
        active.deleted_at = Set(Some(Utc::now()));
        active.updated_at = Set(Utc::now());
        active.updated_by = Set(operator_id);
        active
            .update(db)
            .await
            .map_err(|e| WorkflowError::Validation(e.to_string()))?;

        Ok(())
    }

    fn model_to_resp(m: &process_definition::Model) -> ProcessDefinitionResp {
        ProcessDefinitionResp {
            id: m.id,
            name: m.name.clone(),
            key: m.key.clone(),
            version: m.version,
            category: m.category.clone(),
            description: m.description.clone(),
            nodes: m.nodes.clone(),
            edges: m.edges.clone(),
            status: m.status.clone(),
            created_at: m.created_at,
            updated_at: m.updated_at,
        }
    }
}