use std::collections::HashMap;
use std::path::{Path, PathBuf};
use std::process::Command;

use crate::db::{is_executable, read_extension, read_or_none};
use crate::backend::{Repo, backend};
use crate::log;

/// Defines how tasks are selected to be run
#[derive(Clone, Debug)]
pub enum Select {
    /// Select all tasks (executable files) from a given basedir
    All(PathBuf),
    /// Select all tasks with a matching TASK.inbox from a basedir
    Inbox(PathBuf),
    /// Select all tasks from a basedir with a matching TASK.inbox
    /// in a separate inbox directory.
    InboxDir(PathBuf, String),
    /// Select all tasks from a basedir that are also in a list
    List(PathBuf, Vec<String>),
}

impl Select {
    /// Removes the inbox file for the given task
    pub fn clean(&self, task: &str) {
        match self {
            Select::Inbox(basedir) => {
                std::fs::remove_file(&basedir.join(&format!("{}.inbox", task))).unwrap();
            },
            Select::InboxDir(_basedir, inboxdir) => {
                std::fs::remove_file(&PathBuf::from(inboxdir).join(&format!("{}.inbox", task))).unwrap()
            },
            _ => {},
        }
    }

    /// Find tasks matched by a selection
    pub fn apply(&self, context: &log::Context) -> Result<Vec<Task>, MissingTask> {
        // TODO: Dedicated error type for specific IO errors:
        // - missing basedir/select
        // - permissions problem for basedir/select
        match self {
            // We load all executable entries from basedir
            Select::All(basedir) => {
                Ok(from_dir(basedir, self.clone(), context))
            },

            // We load all entries ending with .inbox from basedir
            Select::Inbox(basedir) => {
                let inbox_entries = basedir.read_dir().unwrap().filter_map(|f| {
                    if f.is_err() {
                        // Dismiss individual file errors
                        return None;
                    }
                    let f_string = f.unwrap().file_name().to_str().unwrap().to_string();
                    if ! f_string.ends_with(".inbox") || f_string.starts_with(".") {
                        // We're only looking for non-hidden *.inbox files
                        return None;
                    }
                    return Some(f_string.trim_end_matches(".inbox").to_string());
                }).collect();
                from_dir_and_list(basedir, inbox_entries, self.clone(), context)
            },

            // We load all entries ending with .inbox from inboxdir
            Select::InboxDir(basedir, inboxdir) => {
                let inbox_entries = PathBuf::from(inboxdir).read_dir().unwrap().filter_map(|f| {
                    if f.is_err() {
                        // Dismiss individual file errors
                        return None;
                    }
                    let f_string = f.unwrap().file_name().to_str().unwrap().to_string();
                    if ! f_string.ends_with(".inbox") || f_string.starts_with(".") {
                        // We're only looking for non-hidden *.inbox files
                        return None;
                    }
                    return Some(f_string.trim_end_matches(".inbox").to_string());
                }).collect();
                from_dir_and_list(basedir, inbox_entries, self.clone(), context)
            },

            // Load all entries from list
            Select::List(basedir, list) => {
                from_dir_and_list(basedir, list.clone(), self.clone(), context)
            },

        }
    }
}

// TODO: Maybe all source/DVCS information should be moved to Repo
// so that task structure is simpler.

#[derive(Debug)]
pub struct Task {
    /// The filename for the task
    pub name: String,
    /// Full path to the task
    pub bin: PathBuf,
    /// Potentially, a source repository to track for updates
    pub source: Option<String>,
    /// The full Repo information
    pub repo: Option<Repo>,
    /// Variables for task config
    pub config: HashMap<String, String>,
    /// Potentially, a branch/commit to track
    pub branch: Option<String>,
    /// List of hosts on which this task should run
    pub hosts: Vec<String>,
    /// Whether the source, if any, has been cloned already
    pub cloned: bool,
    /// Whether to track subrepository/submodule updates
    pub subupdates: bool,
    /// The context in which to store variables for translations
    pub context: log::Context,
    /// The selection context in which a task was created, so that running it can remove it from inbox
    pub select: Select,
}

/// config returns an option of (settings directory, ignored tasks) as
/// (PathBuf, Vec<String>)
pub fn config(basedir: &Path) -> (PathBuf, Vec<String>) {
    let hostname =
        std::env::var("HOST").unwrap_or_else(|_| hostname::get().unwrap().into_string().unwrap());
    let path = basedir.join(hostname);
    if path.is_dir() {
        let ignored = path
            .read_dir()
            .unwrap()
            .filter_map(|x| {
                if x.is_err() {
                    return None;
                }
                let name = x.unwrap().file_name().into_string().unwrap();
                if name.ends_with(".ignore") {
                    return Some(name.trim_end_matches(".ignore").to_string());
                }
                return None;
            })
            .collect();
        (path, ignored)
    } else {
        // TODO: load .ignore in default config?
        (basedir.join("config"), Vec::new())
    }
}
impl Task {
	pub fn from_path(path: &Path, select: Select, context: &log::Context) -> Option<Task> {
		let name = path.file_name().unwrap().to_str().unwrap().to_string();

		// We don't return a task if:
		//  - the path is not a file
		//  - the file is not executable (can't be run)
		//  - the file starts with . (hidden file)
		if !path.is_file() || !is_executable(&path) || name.starts_with('.') {
			return None;
		}

		let basedir = path.parent().unwrap(); // Calling a task in / (FS root) will panic
        let source = read_extension(path, "source");
        let dest = source_dir_from_basedir(&basedir, &name);
        let cloned = source.clone().map_or(false, |_| dest.is_dir());
        let subupdates = read_extension(path, "subupdates").is_some();
        let checkout = read_extension(path, "checkout");

        // Copy the global context so we have a more local scope
        let mut context = context.clone();
        context.insert("$i18n_task".to_string(), name.clone());
        if let Some(branch) = &checkout {
            context.insert("$i18n_branch".to_string(), branch.to_string());
        }
        if let Some(source_url) = &source {
            context.insert("$i18n_source".to_string(), source_url.clone());
        }

        let dvcs = if let Some(dvcs) = backend(read_extension(path, "dvcs")) { dvcs } else {
            // TODO: forgebuild error message
            eprintln!("Unrecognized dvcs for task {}, possible options are 'git' or 'mercurial'. Skipped", &name);
            return None;
        };

        Some(Task {
            name,
            bin: path.to_path_buf(),
            // None source = None repo
            repo: source.as_ref().map(|s| {
                Repo::new(
                    dvcs,
                    s,
                    &dest,
                    subupdates,
                )
            }),
            source,
            config: HashMap::new(),
            branch: checkout,
            hosts: read_extension(path, "hosts").map_or(Vec::new(), |c| {
                c.split("\n").map(|line| line.to_string()).collect()
            }),
            cloned,
            subupdates: read_extension(path, "subupdates").is_some(),
            context,
            select,
        })
    }

    pub fn checkout(&self) {
        if let Some(branch) = &self.branch {
            if let Some(repo) = &self.repo {
                self.info("to_branch");
                self.debug("checkout");
                repo.checkout(branch);
            }
        }
    }

    pub fn run_on_host(&self) -> bool {
        if self.hosts.len() == 0 {
            return true;
        }
        // $HOSTNAME env is a bashism, we need to call libc (through hostname crate)
        // to find out the actual hostname
        let hostname = std::env::var("HOST")
            .unwrap_or_else(|_| hostname::get().unwrap().into_string().unwrap());
        if self.hosts.contains(&hostname) {
            return true;
        }
        return false;
    }

    pub fn update_and_run(&self, force: &bool) {
        if let Some(repo) = &self.repo {
            if repo.update() {
                self.run();
            } else if *force {
                self.debug("forcing");
                self.run();
            } else {
                self.debug("no_update");
            }
        } else {
            unreachable!("this function should never be called on a task whcih doesnt have a repo");
        }
    }

    pub fn run(&self) {
        if !self.run_on_host() {
            // TODO: Skip host debug?
            return;
        }

        self.info("run");
        
        // TODO: debug message for removing inbox
        self.select.clean(&self.name);

        let cmd_out = Command::new("bash") // TODO: no need to call bash?
            .arg(&self.bin)
            .arg(&self.name)
            .output()
            .expect(&format!("Failed to run {:?}", &self.bin));
        let mut log_path = self.bin.clone();
        log_path.set_extension("log");
        std::fs::write(&log_path, cmd_out.stderr)
            .expect(&format!("Failed to write log to {:?}", &log_path));
    }

    pub fn run_once(&self) {
        if !self.run_on_host() {
            return;
        }
        let mut done_path = self.bin.clone();
        done_path.set_extension("done");
        if !done_path.exists() {
            self.run();
            std::fs::write(&done_path, "").expect("Failed to register task as done");
        }
    }

    #[allow(dead_code)]
    pub fn debug(&self, message: &str) {
        log::debug(message, &self.context);
    }

    #[allow(dead_code)]
    pub fn info(&self, message: &str) {
        log::info(message, &self.context);
    }

    #[allow(dead_code)]
    pub fn warn(&self, message: &str) {
        log::warn(message, &self.context);
    }

    #[allow(dead_code)]
    pub fn error(&self, message: &str) {
        log::error(message, &self.context);
    }
}


pub struct MissingTask(pub String);

/// Contains a mapping of sources to their corresponding tasks
pub struct SourceSet {
    mapping: HashMap<String, Vec<String>>,
}

impl SourceSet {

    /// Loads a SourceSet from a basedir
    pub fn from(basedir: &Path) -> Result<SourceSet, std::io::Error> {
        let source_urls = basedir.read_dir()?.filter_map(|p| {
            if p.is_err() { return None; } // Skip individual errors
            let p = p.unwrap().path();
            let path_str = p.to_str().unwrap();
            if !path_str.ends_with(".source") {
                // Filter out non-source files
                return None;
            }
            return Some((
                path_str.trim_end_matches(".source").to_string(), // Task name
                read_or_none(&p).unwrap() // Source URL
            ));
        });

        let mut sources_map: HashMap<String, Vec<String>>  = HashMap::new();
        for (task, source) in source_urls {
            if let Some(list) = sources_map.get_mut(&source) {
                list.push(task.to_string());
            } else {
                sources_map.insert(source.clone(), vec!(task.to_string()));
            }
        }

        Ok(SourceSet {
            mapping: sources_map
        })
    }

    /// Returns the task names associated with a given source
    pub fn tasks_for(&self, source: &str) -> Option<Vec<String>> {
        self.mapping.get(source).map(|x| x.clone())
    }
}

/// Loads a task list from a given base directory, taking only tasks that are in requested list.
/// Given tasks can be either a task name or a task URL. This function will panic if the basedir
/// does not exist, or error if a requested task/source does not exist.
pub fn from_dir_and_list(basedir: &Path, list: Vec<String>, select: Select, context: &log::Context) -> Result<Vec<Task>, MissingTask> {
    // TODO: Write tests for permissions problems

    // If we're looking up specific tasks, maybe they're referenced by source
    // and not by name. SourceSet allows for a source->name mapping.
    let sourceset = SourceSet::from(basedir).unwrap();
    let mut tasks = Vec::new();
    for t in list {
        if let Some(task) = Task::from_path(&basedir.join(&t), select.clone(), context) {
            tasks.push(task);
        } else {
            // Maybe it's not a task name, but a task URL?
            if let Some(list) = sourceset.tasks_for(&t) {
                // Hopefully safe unwrap (unless there's a source without a corresponding task?)
                let task_list = list.iter().map(|t_name| Task::from_path(&basedir.join(&t_name), select.clone(), context).unwrap());
                tasks.extend(task_list);
            } else {
                return Err(MissingTask(t));
            }
        }
    }
    Ok(tasks)
}

/// Loads a task list from a given base directory. Fails if the directory
/// is not readable with std::io::Error.
pub fn from_dir(basedir: &Path, select: Select, context: &log::Context) -> Vec<Task> {
    basedir.read_dir().unwrap().filter_map(|f| {
        if f.is_err() {
            // Dismiss individual file errors
            return None;
        }
        return Task::from_path(&f.unwrap().path(), select.clone(), context);
    }).collect()
}


/// Takes a &Path to a basedir, and a &str task_name, and return
/// the corresponding source directory as a PathBuf. Does not check
/// if the target exists.
pub fn source_dir_from_basedir(basedir: &Path, task_name: &str) -> PathBuf {
	basedir.join(&format!(".{}", task_name))
}