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

use eyre::{bail, eyre, Result, WrapErr};

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

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;

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum ItemSource {
    File {
        name: String,
        line: usize,
    },
    CommandLineOrMakeflags,
    Environment,
    Builtin,
    #[cfg(feature = "full")]
    FunctionCall,
}

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

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

        macros.set(
            "MAKE".to_owned(),
            Macro {
                source: ItemSource::Builtin,
                text: std::env::current_exe().map_or_else(
                    |_| TokenString::text("makers"),
                    |x| TokenString::text(x.to_string_lossy()),
                ),
                #[cfg(feature = "full")]
                eagerly_expanded: false,
            },
        );
        if !args.no_builtin_rules {
            inference_rules.extend(builtin_inference_rules());
            macros.add_builtins();
            for target in builtin_targets() {
                targets.put(target);
            }
        }

        macros.add_env();

        for r#macro in args.macros() {
            if let [name, value] = *r#macro.splitn(2, '=').collect::<Vec<_>>() {
                macros.set(
                    name.into(),
                    Macro {
                        source: ItemSource::CommandLineOrMakeflags,
                        text: TokenString::text(value),
                        #[cfg(feature = "full")]
                        eagerly_expanded: false,
                    },
                );
            }
        }

        #[cfg(feature = "full")]
        {
            let make_cmd_goals = args.targets().collect::<Vec<_>>();
            macros.set(
                "MAKECMDGOALS".to_owned(),
                Macro {
                    source: ItemSource::Builtin,
                    text: TokenString::text(make_cmd_goals.join(" ")),
                    #[cfg(feature = "full")]
                    eagerly_expanded: false,
                },
            );

            if let Ok(curdir) = env::current_dir() {
                macros.set(
                    "CURDIR".to_owned(),
                    Macro {
                        source: ItemSource::Builtin,
                        text: TokenString::text(curdir.to_string_lossy()),
                        #[cfg(feature = "full")]
                        eagerly_expanded: false,
                    },
                );
            }
        }

        Makefile {
            inference_rules: vec![],
            builtin_inference_rules: inference_rules,
            macros,
            targets,
            first_non_special_target,
            args,
            already_inferred: Default::default(),
        }
    }

    pub fn extend(&mut self, new: FinishedMakefileReader) -> Result<()> {
        self.inference_rules.extend(new.inference_rules);
        self.macros.extend(
            new.macros,
            #[cfg(feature = "full")]
            new.macro_exports,
        );
        for (_, target) in new.targets {
            self.targets.put(target);
        }
        if self.first_non_special_target.is_none() {
            self.first_non_special_target = new.first_non_special_target;
        }
        for failed_include in new.failed_includes {
            // try rebuilding
            self.update_target(&failed_include).wrap_err_with(|| {
                format!("while building missing included file {}", &failed_include)
            })?;
            let macros = self.macros.with_overlay();
            let file =
                MakefileReader::read_file(self.args, macros, failed_include, Default::default())?
                    .finish();
            self.extend(file)?;
        }
        Ok(())
    }

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

    fn infer_target(
        &self,
        name: &str,
        banned_rules: Vec<&InferenceRule>,
        banned_names: Vec<&str>,
    ) -> Result<()> {
        if banned_names.contains(&name) {
            bail!("no infinite recursion allowed");
        }
        if self.already_inferred.borrow().contains(name) {
            return Ok(());
        }
        self.already_inferred.borrow_mut().insert(name.to_owned());
        log::trace!("inferring {}, stack = {:?}", name, banned_names);
        let mut new_target = None;

        let follow_gnu = cfg!(feature = "full");

        let vpath_options = match self.macros.get("VPATH") {
            Some(Macro { text, .. }) if follow_gnu => {
                let vpath = self.expand_macros(text, None)?;
                env::split_paths(&vpath).collect()
            }
            _ => vec![],
        };
        // When no target rule is found to update a target, the inference rules shall
        // be checked. The suffix of the target to be built is compared to the list of
        // suffixes specified by the .SUFFIXES special targets. If the .s1 suffix is
        // found in .SUFFIXES...
        // TODO bring back .SUFFIXES for suffix-based rules
        // 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| !banned_rules.contains(rule))
            .filter(|rule| rule.matches(name).unwrap_or(false));
        for rule in inference_rule_candidates {
            log::trace!(
                "{} considering rule to build {:?} from {:?}",
                name,
                &rule.products,
                &rule.prerequisites
            );
            // whose prerequisite file ($*.s2) exists.
            let prereq_paths = rule
                .prereqs(name)?
                .map(|prereq_path_name| {
                    if name == prereq_path_name || banned_names.contains(&&*prereq_path_name) {
                        // we can't build this based on itself! fuck outta here
                        return None;
                    }
                    if self.targets.has(&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())
                        .or_else(|| {
                            let mut banned_rules = banned_rules.clone();
                            banned_rules.push(rule);
                            let mut banned_names = banned_names.clone();
                            banned_names.push(name);
                            self.infer_target(&prereq_path_name, banned_rules, banned_names)
                                .ok()
                                .and_then(|_| {
                                    if self.targets.has(&prereq_path_name) {
                                        Some(prereq_path_name)
                                    } else {
                                        None
                                    }
                                })
                        })
                })
                .collect::<Option<Vec<String>>>();
            if let Some(prereqs) = prereq_paths {
                log::trace!("oh {} is a {}", name, rule);
                new_target = Some(Target {
                    name: name.into(),
                    prerequisites: prereqs,
                    commands: rule.commands.clone(),
                    stem: rule
                        .first_match(name)?
                        .and_then(|x| x.get(1).map(|x| x.as_str().to_owned())),
                    already_updated: Cell::new(false),
                });
                break;
            }
        }

        if let Some(new_target) = new_target {
            self.targets.put(new_target);
        }

        Ok(())
    }

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

        #[cfg(feature = "full")]
        let name = name.strip_prefix("./").unwrap_or(name);

        let exists_but_infer_anyway = if follow_gnu {
            self.targets
                .get(name)
                .map_or(false, |target| target.borrow().commands.is_empty())
        } else {
            false
        };
        if !self.targets.has(name) || exists_but_infer_anyway {
            log::trace!("trying to infer for {}", name);
            self.infer_target(name, vec![], vec![])?;
        }

        let mut new_target = None;
        if !self.targets.has(name) {
            // well, inference didn't work. is there a default?
            if let Some(default) = self.targets.get(".DEFAULT") {
                let commands = default.borrow().commands.clone();
                new_target = Some(Target {
                    name: name.into(),
                    prerequisites: vec![],
                    commands,
                    stem: None,
                    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![],
                        stem: None,
                        already_updated: Cell::new(true),
                    });
                }
            }
        }

        if let Some(new_target) = new_target {
            self.targets.put(new_target);
        }

        Ok(self
            .targets
            .get(name)
            .ok_or_else(|| eyre!("Target {:?} not found!", name))?)
    }

    pub fn update_target(&self, name: &str) -> Result<()> {
        let target = self.get_target(name);
        match target {
            // TODO make this less janky
            Err(err)
                if err.to_string().contains(" not found!")
                    && self.special_target_has_prereq(".PHONY", name) =>
            {
                Ok(())
            }
            _ => target?.borrow().update(self),
        }
    }

    fn expand_macros(&self, text: &TokenString, target: Option<&Target>) -> Result<String> {
        let target = target.cloned();
        let lookup_internal = move |macro_name: &str| {
            let target = target
                .as_ref()
                .ok_or_else(|| eyre!("internal macro but no current target!"))?;
            let macro_pieces = if macro_name.starts_with('@') {
                // The $@ shall evaluate to the full target name of the
                // current target.
                vec![target.name.clone()]
            } else if macro_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 macro_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 macro_name.starts_with('*') {
                // The $* macro shall evaluate to the current target name with
                // its suffix deleted. (GNUism: the match stem)
                vec![target.stem.as_ref().unwrap_or(&target.name).to_owned()]
            } else if macro_name.starts_with('^') {
                target.prerequisites.clone()
            } else {
                unreachable!()
            };

            let macro_pieces = if macro_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 macro_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
            .iter()
            .chain(self.builtin_inference_rules.iter())
        {
            writeln!(f, "{}", rule)?;
        }
        writeln!(f)?;

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

        header(f, "Targets")?;
        writeln!(f, "{}", &self.targets)?;

        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![$(
                InferenceRule::new_suffix(
                    ItemSource::Builtin,
                    prepend_dot!($($second)?).into(),
                    concat!(".", stringify!($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![],
        stem: None,
        already_updated: Cell::new(false),
    }]
}

#[cfg(test)]
mod test {
    use super::*;

    type R = Result<()>;

    #[cfg(feature = "full")]
    #[test]
    fn stem() -> R {
        let args = Args::empty();
        let rule = InferenceRule {
            source: ItemSource::Builtin,
            products: vec!["this-is-a-%-case".to_owned()],
            prerequisites: vec![],
            commands: vec![],
        };
        let file = Makefile {
            inference_rules: vec![rule],
            builtin_inference_rules: vec![],
            macros: MacroSet::new(),
            targets: Default::default(),
            first_non_special_target: None,
            args: &args,
            already_inferred: Default::default(),
        };

        let target = file.get_target("this-is-a-test-case")?;
        assert_eq!(target.borrow().stem, Some("test".to_owned()));
        Ok(())
    }

    #[cfg(feature = "full")]
    #[test]
    fn missing_phony_targets_ignored() -> R {
        let args = Args::empty();
        let target = Target {
            name: "all".to_owned(),
            prerequisites: vec!["missing".to_owned()],
            commands: vec![],
            stem: None,
            already_updated: Cell::new(false),
        };
        let phony = Target {
            name: ".PHONY".to_string(),
            prerequisites: vec!["missing".to_owned()],
            commands: vec![],
            stem: None,
            already_updated: Cell::new(false),
        };

        let targets = DynamicTargetSet::default();
        targets.put(target);
        targets.put(phony);
        let file = Makefile {
            inference_rules: vec![],
            builtin_inference_rules: vec![],
            macros: MacroSet::new(),
            targets,
            first_non_special_target: None,
            args: &args,
            already_inferred: Default::default(),
        };

        assert!(file.update_target("all").is_ok());
        Ok(())
    }
}