use std::cell::{Cell, RefCell};
use std::collections::HashMap;
use std::env;
use std::fmt;
use std::path::Path;
use std::rc::Rc;

use eyre::{eyre, Result};

use crate::args::Args;

mod command_line;
#[cfg(feature = "full")]
mod conditional;
#[cfg(feature = "full")]
mod functions;
mod inference_rules;
mod input;
mod r#macro;
#[cfg(feature = "full")]
mod pattern;
mod target;
mod token;

use inference_rules::InferenceRule;
pub use input::MakefileReader;
use r#macro::Set as MacroSet;
use target::Target;
use token::TokenString;

pub struct Makefile<'a> {
    inference_rules: Vec<InferenceRule>,
    macros: MacroSet<'static, 'static>,
    targets: RefCell<HashMap<String, Rc<RefCell<Target>>>>,
    pub first_non_special_target: Option<String>,
    args: &'a Args,
    // TODO borrow warnings from Python version
}

impl<'a> Makefile<'a> {
    fn special_target_has_prereq(&self, target: &str, name: &str) -> bool {
        let targets = self.targets.borrow();
        match targets.get(target) {
            Some(target) => {
                let target = target.borrow();
                target.prerequisites.is_empty() || target.prerequisites.iter().any(|e| e == name)
            }
            None => false,
        }
    }

    pub fn get_target(&self, name: &str) -> Result<Rc<RefCell<Target>>> {
        // TODO implement .POSIX
        let follow_gnu = true;

        let vpath_options = match self.macros.get("VPATH") {
            Some((_, vpath)) if follow_gnu => {
                let vpath = self.expand_macros(vpath, None)?;
                env::split_paths(&vpath).collect()
            }
            _ => vec![],
        };

        let targets = self.targets.borrow();
        let mut new_target = None;
        let exists_but_infer_anyway = if follow_gnu {
            targets
                .get(name)
                .map_or(false, |target| target.borrow().commands.is_empty())
        } else {
            false
        };
        if !targets.contains_key(name) || exists_but_infer_anyway {
            // When no target rule is found to update a target, the inference rules shall
            // be checked. The suffix of the target to be built...
            let suffix = Path::new(name)
                .extension()
                .map_or_else(String::new, |ext| format!(".{}", ext.to_string_lossy()));
            // is compared to the list of suffixes specified by the .SUFFIXES special
            // targets. If the .s1 suffix is found in .SUFFIXES...
            if self.special_target_has_prereq(".SUFFIXES", &suffix) || suffix.is_empty() {
                // the inference rules shall be searched in the order defined...
                'rules: for rule in self
                    .inference_rules
                    .iter()
                    // for the first .s2.s1 rule...
                    .filter(|rule| rule.product == suffix)
                {
                    // whose prerequisite file ($*.s2) exists.
                    let prereq_path =
                        Path::new(name).with_extension(rule.prereq.trim_start_matches('.'));
                    if let Some(prereq) = std::iter::once(prereq_path.clone())
                        .chain(
                            if prereq_path.is_absolute() {
                                None
                            } else {
                                Some(vpath_options.iter().map(|vpath| vpath.join(&prereq_path)))
                            }
                            .into_iter()
                            .flatten(),
                        )
                        .find(|prereq| prereq.exists())
                    {
                        new_target = Some(Target {
                            name: name.into(),
                            prerequisites: vec![prereq.to_string_lossy().into()],
                            commands: rule.commands.clone(),
                            already_updated: Cell::new(false),
                        });
                        break 'rules;
                    }
                }
            }
        }

        if !targets.contains_key(name) && new_target.is_none() {
            // well, inference didn't work. is there a default?
            if let Some(default) = targets.get(".DEFAULT") {
                let commands = default.borrow().commands.clone();
                new_target = Some(Target {
                    name: name.into(),
                    prerequisites: vec![],
                    commands,
                    already_updated: Cell::new(false),
                });
            } else {
                // if it already exists, it counts as up-to-date
                if Path::new(name).exists() {
                    new_target = Some(Target {
                        name: name.into(),
                        prerequisites: vec![],
                        commands: vec![],
                        already_updated: Cell::new(true),
                    });
                }
            }
        }

        drop(targets);
        if let Some(new_target) = new_target {
            self.targets
                .borrow_mut()
                .insert(new_target.name.clone(), Rc::new(RefCell::new(new_target)));
        }

        let targets = self.targets.borrow();
        Ok(Rc::clone(
            targets
                .get(name)
                .ok_or_else(|| eyre!("Target {:?} not found!", name))?,
        ))
    }

    pub fn update_target(&self, name: &str) -> Result<()> {
        self.get_target(name)?.borrow().update(self)
    }

    fn expand_macros(&self, text: &TokenString, target: Option<&Target>) -> Result<String> {
        let target = target.cloned();
        let lookup_internal = move |name: &str| {
            let target = target
                .as_ref()
                .ok_or_else(|| eyre!("internal macro but no current target!"))?;
            let macro_pieces = if name.starts_with('@') {
                // The $@ shall evaluate to the full target name of the
                // current target.
                vec![target.name.clone()]
            } else if name.starts_with('?') {
                // The $? macro shall evaluate to the list of prerequisites
                // that are newer than the current target.
                target
                    .prerequisites
                    .iter()
                    .filter(|prereq| {
                        self.get_target(prereq)
                            .ok()
                            .and_then(|prereq| prereq.borrow().newer_than(target))
                            .unwrap_or(false)
                    })
                    .cloned()
                    .collect()
            } else if name.starts_with('<') {
                // In an inference rule, the $< macro shall evaluate to the
                // filename whose existence allowed the inference rule to be
                // chosen for the target. In the .DEFAULT rule, the $< macro
                // shall evaluate to the current target name.
                target.prerequisites.clone()
            } else if name.starts_with('*') {
                // The $* macro shall evaluate to the current target name with
                // its suffix deleted.
                vec![Path::new(name).with_extension("").to_string_lossy().into()]
            } else {
                unreachable!()
            };

            let macro_pieces = if name.ends_with('D') {
                macro_pieces
                    .into_iter()
                    .map(|x| {
                        Path::new(&x)
                            .parent()
                            .ok_or_else(|| eyre!("no parent"))
                            .map(|x| x.to_string_lossy().into())
                    })
                    .collect::<Result<_, _>>()?
            } else if name.ends_with('F') {
                macro_pieces
                    .into_iter()
                    .map(|x| {
                        Path::new(&x)
                            .file_name()
                            .ok_or_else(|| eyre!("no filename"))
                            .map(|x| x.to_string_lossy().into())
                    })
                    .collect::<Result<_, _>>()?
            } else {
                macro_pieces
            };

            Ok(macro_pieces.join(" "))
        };

        self.macros.with_lookup(&lookup_internal).expand(text)
    }
}

impl fmt::Display for Makefile<'_> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let header = |f: &mut fmt::Formatter, t: &str| {
            writeln!(f, "{}\n{:=^width$}", t, "", width = t.len())
        };
        header(f, "Inference Rules")?;
        for rule in &self.inference_rules {
            writeln!(f, "{}", rule)?;
        }
        writeln!(f)?;

        header(f, "Macros")?;
        writeln!(f, "{}", &self.macros)?;
        writeln!(f)?;

        header(f, "Targets")?;
        for target in self.targets.borrow().values() {
            writeln!(f, "{}", target.borrow())?;
        }

        Ok(())
    }
}