//! 分组树的管理：多层分组、父级移动与排序。
//!
//! 数据层只有一张 `node` 树：顶层节点是「根分组」（`kind='section'`），
//! 下面的节点都叫分组（`kind='group'`），可以继续嵌套。
//! 条目的展示格式由 `entry.format` 决定，分组不再保存格式。

use rusqlite::{Connection, OptionalExtension, params};
use serde::Deserialize;

use crate::{db::entries, db::map_error, error::StashError};

#[derive(Debug, Clone, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct NewNode {
    /// 业务键，只允许小写字母、数字与连字符
    pub key: String,
    pub title: String,
    /// 为空表示新建一个根分组
    #[serde(default)]
    pub parent_key: Option<String>,
    /// 图标：可以是 iconfont 名或字符；空字符串表示不显示
    #[serde(default)]
    pub icon: Option<String>,
    /// 排序权重；不传则排到同级末尾
    #[serde(default)]
    pub sort: Option<i64>,
    /// 是否启用，默认 true
    #[serde(default)]
    pub enabled: Option<bool>,
}

#[derive(Debug, Clone, Default, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct UpdateNode {
    pub title: Option<String>,
    /// 传入即移动到新的父节点；不支持移回根（根分组请直接新建）
    pub parent_key: Option<String>,
    pub sort: Option<i64>,
    /// 图标：空字符串表示清除图标
    pub icon: Option<String>,
    pub enabled: Option<bool>,
}

fn valid_key(key: &str) -> bool {
    !key.is_empty()
        && key.len() <= 64
        && key
            .chars()
            .all(|ch| ch.is_ascii_lowercase() || ch.is_ascii_digit() || ch == '-')
}

pub fn create(conn: &mut Connection, new: NewNode) -> Result<(), StashError> {
    let key = new.key.trim();
    let title = new.title.trim();

    if !valid_key(key) {
        return Err(StashError::InvalidDirectory(
            "分组标识只能用小写字母、数字与连字符（≤64）".into(),
        ));
    }
    if title.is_empty() || title.chars().count() > 40 {
        return Err(StashError::InvalidDirectory("分组名称需为 1–40 个字".into()));
    }

    let exists: i64 = conn
        .query_row("SELECT COUNT(*) FROM node WHERE key = ?1", [key], |row| {
            row.get(0)
        })
        .map_err(map_error)?;
    if exists > 0 {
        return Err(StashError::Conflict(format!("分组已存在: {key}")));
    }

    let kind = match new.parent_key.as_deref() {
        Some(parent) => {
            let parent_exists: i64 = conn
                .query_row("SELECT COUNT(*) FROM node WHERE key = ?1", [parent], |row| {
                    row.get(0)
                })
                .map_err(map_error)?;
            if parent_exists == 0 {
                return Err(StashError::NotFound(format!("父分组不存在: {parent}")));
            }
            "group"
        }
        None => "section",
    };

    let default_sort: i64 = match new.parent_key.as_deref() {
        Some(parent) => conn
            .query_row(
                "SELECT COALESCE(MAX(sort), 0) + 1 FROM node WHERE parent_key = ?1",
                [parent],
                |row| row.get(0),
            )
            .map_err(map_error)?,
        None => conn
            .query_row(
                "SELECT COALESCE(MAX(sort), 0) + 1 FROM node WHERE parent_key IS NULL",
                [],
                |row| row.get(0),
            )
            .map_err(map_error)?,
    };
    let sort = new.sort.unwrap_or(default_sort);
    let icon = new
        .icon
        .as_deref()
        .map(str::trim)
        .filter(|value| !value.is_empty())
        .map(str::to_string);
    let enabled = new.enabled.unwrap_or(true);

    let tx = conn.transaction().map_err(map_error)?;
    tx.execute(
        "INSERT INTO node (key, parent_key, title, kind, icon, enabled, sort)
         VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7)",
        params![
            key,
            new.parent_key,
            title,
            kind,
            icon,
            enabled,
            sort
        ],
    )
    .map_err(map_error)?;
    entries::audit(&tx, "node.create", key, title)?;
    tx.commit().map_err(map_error)?;
    Ok(())
}

pub fn update(conn: &mut Connection, key: &str, patch: UpdateNode) -> Result<(), StashError> {
    let current: Option<(String, Option<String>, i64, Option<String>, bool)> = conn
        .query_row(
            "SELECT title, parent_key, sort, icon, enabled FROM node WHERE key = ?1",
            [key],
            |row| {
                Ok((
                    row.get(0)?,
                    row.get(1)?,
                    row.get(2)?,
                    row.get(3)?,
                    row.get(4)?,
                ))
            },
        )
        .optional()
        .map_err(map_error)?;

    let Some((current_title, current_parent, current_sort, current_icon, current_enabled)) = current
    else {
        return Err(StashError::NotFound(format!("分组不存在: {key}")));
    };

    let title = match patch.title {
        Some(title) => {
            let title = title.trim().to_string();
            if title.is_empty() || title.chars().count() > 40 {
                return Err(StashError::InvalidDirectory("分组名称需为 1–40 个字".into()));
            }
            title
        }
        None => current_title,
    };

    let parent_key = match patch.parent_key.clone() {
        Some(parent) => {
            if parent == key {
                return Err(StashError::InvalidDirectory("不能把分组移到自己下面".into()));
            }
            let exists: i64 = conn
                .query_row("SELECT COUNT(*) FROM node WHERE key = ?1", [&parent], |row| {
                    row.get(0)
                })
                .map_err(map_error)?;
            if exists == 0 {
                return Err(StashError::NotFound(format!("父分组不存在: {parent}")));
            }
            // 防止把节点移进自己的子孙
            let mut cursor = Some(parent.clone());
            while let Some(candidate) = cursor {
                if candidate == key {
                    return Err(StashError::InvalidDirectory(
                        "不能把分组移到自己的子分组下面".into(),
                    ));
                }
                cursor = conn
                    .query_row(
                        "SELECT parent_key FROM node WHERE key = ?1",
                        [candidate],
                        |row| row.get::<_, Option<String>>(0),
                    )
                    .optional()
                    .map_err(map_error)?
                    .flatten();
            }
            Some(parent)
        }
        // 不传表示保持原父级（不支持移回根）
        None => current_parent.clone(),
    };

    let icon = match patch.icon {
        Some(icon) => {
            let icon = icon.trim().to_string();
            (!icon.is_empty()).then_some(icon)
        }
        None => current_icon,
    };
    let enabled = patch.enabled.unwrap_or(current_enabled);

    let sort = patch.sort.unwrap_or(current_sort);

    let tx = conn.transaction().map_err(map_error)?;
    // 只有真正换了父级才排到末尾；同一父级下编辑排序权重时按传入值保存
    let parent_changed = patch
        .parent_key
        .as_deref()
        .is_some_and(|parent| Some(parent) != current_parent.as_deref());
    let final_sort = if parent_changed {
        let parent = patch.parent_key.as_deref().unwrap_or_default();
        tx.query_row(
            "SELECT COALESCE(MAX(sort), 0) + 1 FROM node WHERE parent_key = ?1 AND key <> ?2",
            params![parent, key],
            |row| row.get::<_, i64>(0),
        )
        .map_err(map_error)?
    } else {
        sort
    };

    tx.execute(
        "UPDATE node SET title = ?1, parent_key = ?2, sort = ?3,
                icon = ?4, enabled = ?5
         WHERE key = ?6",
        params![title, parent_key, final_sort, icon, enabled, key],
    )
    .map_err(map_error)?;
    entries::audit(&tx, "node.update", key, &title)?;
    tx.commit().map_err(map_error)?;
    Ok(())
}

pub fn remove(conn: &Connection, key: &str) -> Result<(), StashError> {
    let removed = conn
        .execute("DELETE FROM node WHERE key = ?1", [key])
        .map_err(map_error)?;
    if removed == 0 {
        return Err(StashError::NotFound(format!("分组不存在: {key}")));
    }
    entries::audit(conn, "node.delete", key, "")?;
    Ok(())
}