use std::cell::{Cell, RefCell};
use std::collections::HashMap;
use std::fmt;
use std::fs::metadata;
use std::mem;
use std::rc::Rc;
use std::time::SystemTime;

use eyre::{Result, WrapErr};

use super::{CommandLine, MacroSet, Makefile};

#[derive(PartialEq, Eq, Clone, Debug)]
pub struct Target {
    pub name: String,
    pub prerequisites: Vec<String>,
    pub commands: Vec<CommandLine>,
    pub stem: Option<String>,
    pub already_updated: Cell<bool>,
    pub macros: MacroSet,
}

impl Target {
    pub fn extend(&mut self, other: Self) {
        assert_eq!(&self.name, &other.name);
        match (self.commands.is_empty(), other.commands.is_empty()) {
            (false, false) => {
                // both targets have commands, so replace this entirely
                *self = other;
            }
            (true, false) => {
                // this target doesn't have commands, but the other one does,
                // so it's the real one
                let mut other = other;
                mem::swap(self, &mut other);
                self.extend(other);
            }
            (false, true) | (true, true) => {
                // this target might have commands, but the other one doesn't,
                // so append non-command stuff
                self.prerequisites.extend(other.prerequisites);
                self.stem = self.stem.take().or(other.stem);
                let already_updated = self.already_updated.get() || other.already_updated.get();
                self.already_updated.set(already_updated);
                self.macros.extend(other.macros);
            }
        }
    }

    fn modified_time(&self) -> Option<SystemTime> {
        metadata(&self.name)
            .and_then(|metadata| metadata.modified())
            .ok()
    }

    pub fn newer_than(&self, other: &Self) -> Option<bool> {
        let self_updated = self.already_updated.get();
        let other_updated = other.already_updated.get();
        Some(match (self.modified_time(), other.modified_time()) {
            (Some(self_mtime), Some(other_mtime)) => self_mtime >= other_mtime,
            // per POSIX: "If the target does not exist after the target has been
            // successfully made up-to-date, the target shall be treated as being
            // newer than any target for which it is a prerequisite."
            (None, _) if self_updated && other.prerequisites.contains(&self.name) => true,
            (_, None) if other_updated && self.prerequisites.contains(&other.name) => false,
            _ => return None,
        })
    }

    pub fn is_up_to_date(&self, file: &Makefile) -> bool {
        if self.already_updated.get() {
            return true;
        }
        #[cfg(feature = "full")]
        if file.special_target_has_prereq(".PHONY", &self.name) {
            return false;
        }
        let exists = metadata(&self.name).is_ok();
        let newer_than_all_dependencies = self.prerequisites.iter().all(|t| {
            file.get_target(t)
                .ok()
                .and_then(|t| self.newer_than(&t.borrow()))
                .unwrap_or(false)
        });
        log::trace!(
            "{:} exists: {}, newer than dependencies: {}",
            self.name,
            exists,
            newer_than_all_dependencies
        );
        exists && newer_than_all_dependencies
    }

    pub fn update(&self, file: &Makefile) -> Result<()> {
        log::info!("{}: {:?}", &self.name, &self.prerequisites);
        for prereq in &self.prerequisites {
            file.update_target(prereq)
                .wrap_err_with(|| format!("as a dependency for target {}", self.name))?;
        }
        if !self.is_up_to_date(file) {
            log::debug!("rebuilding {}...", self.name);
            if self.commands.is_empty() {
                log::warn!("no commands found to rebuild {}", self.name);
            }
            self.execute_commands(file)
                .wrap_err_with(|| format!("while updating target {}", self.name))?;
        }
        self.already_updated.set(true);

        Ok(())
    }

    fn execute_commands(&self, file: &Makefile) -> Result<()> {
        for command in &self.commands {
            log::trace!("  executing {}", command);
            command.execute(file, self)?;
        }

        Ok(())
    }
}

impl fmt::Display for Target {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let prereqs = self.prerequisites.join(" ");
        writeln!(f, "{}: {}", &self.name, prereqs)?;
        for command in &self.commands {
            writeln!(f, "\t{}", command)?;
        }
        Ok(())
    }
}

// for targets that won't change out from under us (don't need refcelling)
#[derive(Clone, Default)]
pub struct StaticTargetSet {
    data: HashMap<String, Target>,
}

impl StaticTargetSet {
    pub fn get(&self, name: &str) -> Option<&Target> {
        self.data.get(name)
    }

    pub fn put(&mut self, target: Target) {
        if target.name == ".SUFFIXES" && target.prerequisites.is_empty() {
            self.data.remove(&target.name);
        }
        if let Some(existing_target) = self.data.get_mut(&target.name) {
            existing_target.extend(target);
        } else {
            self.data.insert(target.name.clone(), target);
        }
    }
}

impl From<StaticTargetSet> for HashMap<String, Target> {
    fn from(value: StaticTargetSet) -> Self {
        value.data
    }
}

// for targets that might become updated and so need refcelling
#[derive(Clone, Default)]
pub struct DynamicTargetSet {
    data: RefCell<HashMap<String, Rc<RefCell<Target>>>>,
}

impl DynamicTargetSet {
    pub fn get(&self, name: &str) -> Option<Rc<RefCell<Target>>> {
        self.data.borrow().get(name).map(Rc::clone)
    }

    pub fn put(&self, target: Target) {
        if let Some(existing_target) = self.data.borrow().get(&target.name) {
            existing_target.borrow_mut().extend(target);
            return;
        }
        self.data
            .borrow_mut()
            .insert(target.name.clone(), Rc::new(RefCell::new(target)));
    }

    pub fn has(&self, name: &str) -> bool {
        self.data.borrow().contains_key(name)
    }
}

impl fmt::Display for DynamicTargetSet {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        for target in self.data.borrow().values() {
            writeln!(f, "{}", target.borrow())?;
        }
        Ok(())
    }
}