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

use eyre::{bail, 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;
mod pattern;
mod target;
mod token;

use command_line::CommandLine;
use inference_rules::InferenceRule;
use input::FinishedMakefileReader;
pub use input::MakefileReader;
use r#macro::{Set as MacroSet, Source as MacroSource};
use target::Target;
use token::TokenString;

pub struct Makefile<'a> {
    inference_rules: Vec<InferenceRule>,
    builtin_inference_rules: Vec<InferenceRule>,
    pub 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
    fucking_bullshit_recursion_stack: RefCell<Vec<String>>,
}

impl<'a> Makefile<'a> {
    pub fn new(args: &'a Args) -> Self {
        let mut inference_rules = vec![];
        let mut macros = MacroSet::new();
        let mut targets = HashMap::new();
        let first_non_special_target = None;

        if !args.no_builtin_rules {
            inference_rules.extend(builtin_inference_rules());
            macros.add_builtins();
            targets.extend(
                builtin_targets()
                    .into_iter()
                    .map(|t| (t.name.clone(), Rc::new(RefCell::new(t)))),
            );
        }

        macros.add_env();

        for r#macro in args.macros() {
            if let [name, value] = *r#macro.splitn(2, '=').collect::<Vec<_>>() {
                macros.set(
                    name.into(),
                    MacroSource::CommandLineOrMakeflags,
                    TokenString::text(value),
                );
            }
        }

        Makefile {
            inference_rules: vec![],
            builtin_inference_rules: inference_rules,
            macros,
            targets: RefCell::new(targets),
            first_non_special_target,
            args,
            fucking_bullshit_recursion_stack: RefCell::new(Vec::new()),
        }
    }

    pub fn extend(&mut self, new: FinishedMakefileReader) {
        self.inference_rules.extend(new.inference_rules);
        self.macros.extend(new.macros);
        self.targets.borrow_mut().extend(
            new.targets
                .into_iter()
                .map(|(k, v)| (k, Rc::new(RefCell::new(v)))),
        );
        if self.first_non_special_target.is_none() {
            self.first_non_special_target = new.first_non_special_target;
        }
    }

    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>>> {
        if self
            .fucking_bullshit_recursion_stack
            .borrow()
            .contains(&name.to_owned())
        {
            bail!("no infinite recursion allowed");
        }
        self.fucking_bullshit_recursion_stack
            .borrow_mut()
            .push(name.to_owned());
        // TODO implement .POSIX
        let follow_gnu = cfg!(feature = "full");

        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 mut new_target = None;
        let exists_but_infer_anyway = if follow_gnu {
            self.targets
                .borrow()
                .get(name)
                .map_or(false, |target| target.borrow().commands.is_empty())
        } else {
            false
        };
        if !self.targets.borrow().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...
            // TODO figure out if .SUFFIXES is supposed to apply to gnuful patterns
            if self.special_target_has_prereq(".SUFFIXES", &suffix) || suffix.is_empty() {
                // the inference rules shall be searched in the order defined...
                // TODO implement GNUish shortest-stem-first matching
                let inference_rule_candidates = self
                    .inference_rules
                    .iter()
                    .chain(self.builtin_inference_rules.iter())
                    .filter(|rule| rule.matches(name).unwrap_or(false));
                for rule in inference_rule_candidates {
                    log::trace!(
                        "{:>58} considering rule to build {:?} from {:?}",
                        name,
                        &rule.products,
                        &rule.prerequisites
                    );
                    // whose prerequisite file ($*.s2) exists.
                    let prereq_paths = rule
                        .prereqs(name)?
                        .inspect(|x| log::trace!("{:>58} prereq {}", name, x))
                        .map(|prereq_path_name| {
                            if name == prereq_path_name {
                                // we can't build this based on itself! fuck outta here
                                return None;
                            }
                            // TODO allow chains but only reluctantly
                            if self.targets.borrow().contains_key(&prereq_path_name) {
                                return Some(prereq_path_name);
                            }
                            let prereq_path = PathBuf::from(prereq_path_name);
                            let prereq_vpath_options = if prereq_path.is_absolute() {
                                None
                            } else {
                                Some(vpath_options.iter().map(|vpath| vpath.join(&prereq_path)))
                            }
                            .into_iter()
                            .flatten();
                            std::iter::once(prereq_path.clone())
                                .chain(prereq_vpath_options)
                                .find(|prereq| prereq.exists())
                                .map(|path| path.to_string_lossy().to_string())
                        })
                        .collect::<Option<Vec<String>>>();
                    if let Some(prereqs) = prereq_paths {
                        new_target = Some(Target {
                            name: name.into(),
                            prerequisites: prereqs,
                            commands: rule.commands.clone(),
                            already_updated: Cell::new(false),
                        });
                        break;
                    }
                }
            }
        }

        let targets = self.targets.borrow();
        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)));
        }

        self.fucking_bullshit_recursion_stack.borrow_mut().pop();

        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.
                // TODO make that actually be the case (rn exists_but_inferring_anyway might fuck that up)
                vec![target.prerequisites.get(0).cloned().unwrap_or_default()]
            } 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(())
    }
}

fn builtin_inference_rules() -> Vec<InferenceRule> {
    // This is a terrible idea.
    macro_rules! prepend_dot {
        ($x:tt) => {
            concat!(".", stringify!($x))
        };
        () => {
            ""
        };
    }

    macro_rules! make {
        {$(.$first:tt$(.$second:tt)?:
            $($cmd:literal)+)+} => {
            vec![$(
                InferenceRule::new_suffix(
                    prepend_dot!($($second)?).into(),
                    concat!(".", stringify!($first)).into(),
                    vec![$(CommandLine::from($cmd.parse().unwrap())),+],
                )
            ),+]
        };
    }

    make! {
        .c:
            "$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<"
        .f:
            "$(FC) $(FFLAGS) $(LDFLAGS) -o $@ $<"
        .sh:
            "cp $< $@"
            "chmod a+x $@"

        .c.o:
            "$(CC) $(CFLAGS) -c $<"
        .f.o:
            "$(FC) $(FFLAGS) -c $<"
        .y.o:
            "$(YACC) $(YFLAGS) $<"
            "$(CC) $(CFLAGS) -c y.tab.c"
            "rm -f y.tab.c"
            "mv y.tab.o $@"
        .l.o:
            "$(LEX) $(LFLAGS) $<"
            "$(CC) $(CFLAGS) -c lex.yy.c"
            "rm -f lex.yy.c"
            "mv lex.yy.o $@"
        .y.c:
            "$(YACC) $(YFLAGS) $<"
            "mv y.tab.c $@"
        .l.c:
            "$(LEX) $(LFLAGS) $<"
            "mv lex.yy.c $@"
        .c.a:
            "$(CC) -c $(CFLAGS) $<"
            "$(AR) $(ARFLAGS) $@ $*.o"
            "rm -f $*.o"
        .f.a:
            "$(FC) -c $(FFLAGS) $<"
            "$(AR) $(ARFLAGS) $@ $*.o"
            "rm -f $*.o"
    }
}
fn builtin_targets() -> Vec<Target> {
    // even i'm not going to do that just for this
    vec![Target {
        name: ".SUFFIXES".into(),
        prerequisites: vec![".o", ".c", ".y", ".l", ".a", ".sh", ".f"]
            .into_iter()
            .map(String::from)
            .collect(),
        commands: vec![],
        already_updated: Cell::new(false),
    }]
}