use std::fs::File;
use std::io::Write;

use crate::domain;
use crate::repo::{Error, InsertTaskData, Repository, UpdateTaskData};

use serde::{Deserialize, Serialize};
use xdg::BaseDirectories;

#[derive(Deserialize, Serialize, Clone)]
pub struct Task {
    name: String,
    link: Option<String>,
    group: Option<String>,
    // created_at
}

impl From<Task> for domain::Task {
    fn from(repo: Task) -> Self {
        domain::Task {
            name: repo.name,
            link: repo.link,
            group: repo.group,
        }
    }
}

#[derive(Deserialize, Serialize, Clone)]
pub struct CurrentTaskInfo {
    task_idx: usize,
    task: Task,
    // started_at
}

impl From<CurrentTaskInfo> for domain::CurrentTaskInfo {
    fn from(repo: CurrentTaskInfo) -> Self {
        domain::CurrentTaskInfo {
            task_idx: repo.task_idx,
            task: repo.task.into(),
        }
    }
}

const CURRENT_TASK_FILE: &str = "current.json";
const DATA_FILE: &str = "data.json";
const FINISHED_DATA_FILE: &str = "finished_data.json";

pub struct FsRepo {
    xdg_dirs: BaseDirectories,
}

impl FsRepo {
    pub fn new(xdg_dirs: BaseDirectories) -> Self {
        Self { xdg_dirs }
    }
}

impl Repository for FsRepo {
    fn get_current_task_opt(&self) -> Result<Option<domain::CurrentTaskInfo>, Error> {
        self.get_current_task_impl()
            .map(|cur_task| cur_task.map(From::from))
    }

    fn get_task_opt(&self, id: domain::TaskId) -> Result<Option<domain::Task>, Error> {
        let tasks = self.get_tasks_impl()?;
        if id == 0 || id > tasks.len() {
            return Err(Error::NotFound);
        }

        Ok(Some(tasks[id - 1].clone().into()))
    }

    fn get_tasks(&self) -> Result<Vec<domain::Task>, Error> {
        self.get_tasks_impl()
            .map(|tasks| tasks.into_iter().map(Task::into).collect())
    }

    fn remove_task(&self, id: domain::TaskId) -> Result<domain::Task, Error> {
        let mut tasks = self.get_tasks_impl()?;
        if id == 0 || id > tasks.len() {
            return Err(Error::NotFound);
        }

        let removed = tasks.remove(id - 1);
        self.save_tasks_impl(tasks)?;

        Ok(removed.into())
    }

    fn update_task(
        &self,
        id: domain::TaskId,
        update_data: UpdateTaskData,
    ) -> Result<domain::Task, Error> {
        let mut tasks = self.get_tasks_impl()?;
        if id == 0 || id > tasks.len() {
            return Err(Error::NotFound);
        }

        let mut task = &mut tasks[id - 1];
        if let Some(name) = update_data.name {
            task.name = name;
        }

        if let Some(link) = update_data.link {
            task.link = link;
        }

        if let Some(group) = update_data.group {
            task.group = group;
        }

        let new_task = task.clone();

        self.save_tasks_impl(tasks)?;

        Ok(new_task.into())
    }

    fn insert_task(&self, insert_data: InsertTaskData) -> Result<domain::Task, Error> {
        let new_task = Task {
            name: insert_data.name,
            link: insert_data.link,
            group: insert_data.group,
        };

        let mut tasks = self.get_tasks_impl()?;

        match insert_data.index {
            None => tasks.push(new_task.clone()),
            Some(idx) => tasks.insert(idx, new_task.clone()),
        }

        self.save_tasks_impl(tasks)?;

        Ok(new_task.into())
    }

    fn start_task(&self, id: domain::TaskId) -> Result<domain::Task, Error> {
        let tasks = self.get_tasks_impl()?;
        if id == 0 || id > tasks.len() {
            return Err(Error::NotFound);
        }

        let task = &tasks[id - 1];
        let mut cur_task = self.get_current_task_impl()?;

        cur_task.replace(CurrentTaskInfo {
            task_idx: id,
            task: task.clone(),
        });

        self.save_current_task_impl(cur_task)?;
        Ok(task.clone().into())
    }

    fn stop_task(&self) -> Result<domain::Task, Error> {
        let mut cur_task = self.get_current_task_impl()?;
        let old = cur_task.take().ok_or(Error::NotFound)?;
        self.save_current_task_impl(cur_task)?;
        Ok(old.task.into())
    }

    fn finish_task(&self) -> Result<domain::Task, Error> {
        let mut cur_task = self.get_current_task_impl()?;
        let old = cur_task.take().ok_or(Error::NotFound)?;

        let mut finished_tasks = self.get_finished_tasks_impl()?;
        let mut tasks = self.get_tasks_impl()?;

        let task = tasks.remove(old.task_idx - 1);
        finished_tasks.push(task.clone());

        self.save_current_task_impl(cur_task)?;
        self.save_tasks_impl(tasks)?;
        self.save_finished_tasks_impl(finished_tasks)?;

        Ok(task.into())
    }
}

impl FsRepo {
    fn get_current_task_impl(&self) -> Result<Option<CurrentTaskInfo>, Error> {
        let file_path = self.xdg_dirs.get_data_file(CURRENT_TASK_FILE);
        Ok(File::open(&file_path)
            .ok()
            .and_then(|file| serde_json::from_reader(file).ok()))
    }

    fn save_current_task_impl(&self, cur_task: Option<CurrentTaskInfo>) -> Result<(), Error> {
        let file_path = self
            .xdg_dirs
            .place_data_file(CURRENT_TASK_FILE)
            .map_err(|_| Error::InsertData)?;
        let mut file = File::create(&file_path).map_err(|_| Error::InsertData)?;
        let new_data = serde_json::to_vec(&cur_task).map_err(|_| Error::InvalidData)?;
        file.write_all(&new_data).map_err(|_| Error::InsertData)
    }

    fn get_tasks_impl(&self) -> Result<Vec<Task>, Error> {
        let file_path = self.xdg_dirs.get_data_file(DATA_FILE);
        File::open(&file_path)
            .ok()
            .map(|file| serde_json::from_reader(file).map_err(|_| Error::InvalidData))
            .transpose()
            .map(|tasks| tasks.unwrap_or_default())
    }

    fn save_tasks_impl(&self, tasks: Vec<Task>) -> Result<(), Error> {
        let file_path = self
            .xdg_dirs
            .place_data_file(DATA_FILE)
            .map_err(|_| Error::InsertData)?;
        let mut file = File::create(&file_path).map_err(|_| Error::InsertData)?;
        let new_data = serde_json::to_vec(&tasks).map_err(|_| Error::InvalidData)?;
        file.write_all(&new_data).map_err(|_| Error::InsertData)
    }

    fn get_finished_tasks_impl(&self) -> Result<Vec<Task>, Error> {
        let file_path = self.xdg_dirs.get_data_file(FINISHED_DATA_FILE);
        File::open(&file_path)
            .ok()
            .map(|file| serde_json::from_reader(file).map_err(|_| Error::InvalidData))
            .transpose()
            .map(|tasks| tasks.unwrap_or_default())
    }

    fn save_finished_tasks_impl(&self, tasks: Vec<Task>) -> Result<(), Error> {
        let file_path = self
            .xdg_dirs
            .place_data_file(FINISHED_DATA_FILE)
            .map_err(|_| Error::InsertData)?;
        let mut file = File::create(&file_path).map_err(|_| Error::InsertData)?;
        let new_data = serde_json::to_vec(&tasks).map_err(|_| Error::InvalidData)?;
        file.write_all(&new_data).map_err(|_| Error::InsertData)
    }
}