use std::cell::{Cell, RefCell};
use std::collections::HashMap;
use std::error::Error as StdError;
use std::fs::File;
use std::io::{BufRead, BufReader, Error as IoError, ErrorKind as IoErrorKind, Lines};
use std::iter::Peekable;
use std::path::Path;
use std::rc::Rc;

use eyre::{bail, eyre, Context, Result};
use lazy_static::lazy_static;
use regex::Regex;

use crate::args::Args;

#[cfg(feature = "full")]
use super::conditional::{Line as ConditionalLine, State as ConditionalState};
#[cfg(feature = "full")]
use super::eval_context::DeferredEvalContext;
#[cfg(feature = "full")]
use super::r#macro::ExportConfig;
use super::r#macro::Macro;
use super::target::StaticTargetSet;
use super::token::Token;
use super::{
    builtin_targets, CommandLine, InferenceRule, ItemSource, LookupInternal, MacroScopeStack,
    MacroSet, Target, TokenString,
};

enum LineType {
    Rule,
    Macro,
    Include,
    #[cfg(feature = "full")]
    Export,
    #[cfg(feature = "full")]
    Unexport,
    Unknown,
}

impl LineType {
    fn of(line_tokens: &TokenString) -> Self {
        #[cfg(feature = "full")]
        if line_tokens.starts_with("define ") {
            return Self::Macro;
        }
        if line_tokens.starts_with("include ") || line_tokens.starts_with("-include ") {
            return Self::Include;
        }
        #[cfg(feature = "full")]
        if line_tokens.starts_with("export ") || line_tokens == "export" {
            return Self::Export;
        }
        #[cfg(feature = "full")]
        if line_tokens.starts_with("unexport ") || line_tokens == "unexport" {
            return Self::Unexport;
        }
        for token in line_tokens.tokens() {
            if let Token::Text(text) = token {
                let colon_idx = text.find(':');
                #[cfg(not(feature = "full"))]
                let equals_idx = text.find('=');
                #[cfg(feature = "full")]
                let equals_idx = ["=", ":=", "::=", "?=", "+="]
                    .iter()
                    .filter_map(|p| text.find(p))
                    .min();
                match (colon_idx, equals_idx) {
                    (Some(_), None) => {
                        return Self::Rule;
                    }
                    (Some(c), Some(e)) if c < e => {
                        return Self::Rule;
                    }
                    (None, Some(_)) => {
                        return Self::Macro;
                    }
                    (Some(c), Some(e)) if e <= c => {
                        return Self::Macro;
                    }
                    _ => {}
                }
            }
        }
        Self::Unknown
    }
}

#[derive(Debug)]
struct InferenceMatch<'a> {
    s1: &'a str,
    s2: &'a str,
}

fn inference_match<'a>(
    targets: &[&'a str],
    prerequisites: &[String],
) -> Option<InferenceMatch<'a>> {
    lazy_static! {
        static ref INFERENCE_RULE: Regex = #[allow(clippy::unwrap_used)]
        Regex::new(r"^(?P<s2>(\.[^/.]+)?)(?P<s1>\.[^/.]+)$")
            .unwrap();
        static ref SPECIAL_TARGET: Regex = #[allow(clippy::unwrap_used)]
        Regex::new(r"^\.[A-Z]+$").unwrap();
    }

    let inference_match = INFERENCE_RULE.captures(targets[0]);
    let special_target_match = SPECIAL_TARGET.captures(targets[0]);

    let inference_rule = targets.len() == 1
        && prerequisites.is_empty()
        && inference_match.is_some()
        && special_target_match.is_none();
    if inference_rule {
        #[allow(clippy::unwrap_used)]
        inference_match.map(|x| InferenceMatch {
            s1: x.name("s1").unwrap().as_str(),
            s2: x.name("s2").unwrap().as_str(),
        })
    } else {
        None
    }
}

struct LineNumbers<T, E, Inner>(Inner, usize)
where
    E: StdError + Send + Sync + 'static,
    Inner: Iterator<Item = Result<T, E>>;

impl<T, E, Inner> LineNumbers<T, E, Inner>
where
    E: StdError + Send + Sync + 'static,
    Inner: Iterator<Item = Result<T, E>>,
{
    const fn new(inner: Inner) -> Self {
        Self(inner, 0)
    }
}

impl<T, E, Inner> Iterator for LineNumbers<T, E, Inner>
where
    E: StdError + Send + Sync + 'static,
    Inner: Iterator<Item = Result<T, E>>,
{
    type Item = (usize, Result<T>);

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next().map(|x| {
            self.1 = self.1.saturating_add(1);
            (
                self.1,
                x.with_context(|| format!("failed to read line {} of makefile", self.1)),
            )
        })
    }
}

trait IteratorExt<T, E: StdError + Send + Sync + 'static>: Iterator<Item = Result<T, E>> {
    fn line_numbered(self) -> LineNumbers<T, E, Self>
    where
        Self: Sized,
    {
        LineNumbers::new(self)
    }
}
impl<T, E: StdError + Send + Sync + 'static, I: Iterator<Item = Result<T, E>>> IteratorExt<T, E>
    for I
{
}

#[derive(Clone, Copy)]
struct NextLineSettings {
    escaped_newline_replacement: &'static str,
    peeking: bool,
    strip_comments: bool,
}

impl Default for NextLineSettings {
    fn default() -> Self {
        Self {
            escaped_newline_replacement: " ",
            peeking: false,
            strip_comments: true,
        }
    }
}

pub struct MakefileReader<'a, 'parent, R: BufRead> {
    file_name: String,
    pub inference_rules: Vec<InferenceRule>,
    pub stack: MacroScopeStack<'parent>,
    pub macros: MacroSet,
    pub targets: StaticTargetSet,
    built_in_targets: HashMap<String, Target>,
    pub first_non_special_target: Option<String>,
    pub failed_includes: Vec<String>,
    pub args: &'a Args,
    lines_iter: Peekable<LineNumbers<String, IoError, Lines<R>>>,
    // join with escaped_newline_replacement to get the actual line
    pending_line: Option<(usize, Vec<String>)>,
    #[cfg(feature = "full")]
    conditional_stack: Vec<ConditionalState>,
    pub file_names: Rc<RefCell<Vec<String>>>,
}

impl<'a, 'parent> MakefileReader<'a, 'parent, BufReader<File>> {
    pub fn read_file(
        args: &'a Args,
        stack: MacroScopeStack<'parent>,
        path: impl AsRef<Path>,
        file_names: Rc<RefCell<Vec<String>>>,
    ) -> Result<Self> {
        let mut macros = MacroSet::new();
        #[cfg(feature = "full")]
        if let Some(mut old_makefile_list) = macros.pop("MAKEFILE_LIST") {
            old_makefile_list.text.extend(TokenString::text(format!(
                " {}",
                path.as_ref().to_string_lossy()
            )));
            macros.set("MAKEFILE_LIST".to_owned(), old_makefile_list);
        } else {
            macros.set(
                "MAKEFILE_LIST".to_owned(),
                Macro {
                    source: ItemSource::Builtin,
                    text: TokenString::text(path.as_ref().to_string_lossy()),
                    #[cfg(feature = "full")]
                    eagerly_expanded: false,
                },
            );
        }
        let file_name = path.as_ref().to_string_lossy();
        file_names.borrow_mut().push(file_name.to_string());
        let file = File::open(path.as_ref());
        // TODO handle errors
        let file = file.context("couldn't open makefile!")?;
        let file_reader = BufReader::new(file);
        Self::read(args, stack, macros, file_reader, file_name, file_names)
    }
}

impl<'a, 'parent, R: BufRead> MakefileReader<'a, 'parent, R> {
    pub fn read(
        args: &'a Args,
        stack: MacroScopeStack<'parent>,
        macros: MacroSet,
        source: R,
        name: impl Into<String>,
        file_names: Rc<RefCell<Vec<String>>>,
    ) -> Result<Self> {
        let name = name.into();
        let mut reader = Self {
            file_name: name.clone(),
            inference_rules: Vec::new(),
            stack,
            macros,
            targets: Default::default(),
            built_in_targets: HashMap::new(),
            first_non_special_target: None,
            failed_includes: Vec::new(),
            args,
            lines_iter: source.lines().line_numbered().peekable(),
            pending_line: None,
            #[cfg(feature = "full")]
            conditional_stack: Vec::new(),
            file_names,
        };
        // TODO be smart about this instead, please
        if !args.no_builtin_rules {
            reader.built_in_targets.extend(
                builtin_targets()
                    .into_iter()
                    .map(|target| (target.name.clone(), target)),
            );
        }
        reader
            .read_all()
            .wrap_err_with(|| format!("while reading {}", name))?;
        Ok(reader)
    }

    fn read_all(&mut self) -> Result<()> {
        let topmost = NextLineSettings {
            escaped_newline_replacement: " ",
            ..Default::default()
        };
        while let Some((line_number, line)) = self.next_line(topmost) {
            let line = line?;

            if line.trim().is_empty() {
                // handle blank lines
                continue;
            }
            // unfortunately, rules vs macros can't be determined until after
            // macro tokenizing. so that's suboptimal.

            // TODO errors
            let line_tokens: TokenString = line
                .parse()
                .with_context(|| format!("failed to parse line {}", line_number))?;

            let line_type = LineType::of(&line_tokens);

            // before we actually test it, see if it's only visible after expanding macros
            let (line_tokens, line_type) = if matches!(line_type, LineType::Unknown) {
                let line_tokens = TokenString::text(
                    self.expand_macros(&line_tokens)
                        .wrap_err_with(|| format!("while parsing line {}", line_number))?
                        .trim(),
                );
                let line_type = LineType::of(&line_tokens);
                (line_tokens, line_type)
            } else {
                (line_tokens, line_type)
            };

            match line_type {
                LineType::Rule => {
                    self.read_rule(line_tokens, line_number).wrap_err_with(|| {
                        format!(
                            "while parsing rule definition starting on line {}",
                            line_number
                        )
                    })?;
                }
                LineType::Macro => {
                    self.read_macro(line_tokens, line_number)
                        .wrap_err_with(|| {
                            format!(
                                "while parsing macro definition starting on line {}",
                                line_number
                            )
                        })?;
                }
                LineType::Include => {
                    self.read_include(line_tokens, line_number)
                        .wrap_err_with(|| {
                            format!("while parsing include starting on line {}", line_number)
                        })?;
                }
                #[cfg(feature = "full")]
                LineType::Export => {
                    let mut line_tokens = line_tokens;
                    line_tokens.strip_prefix("export");
                    if line_tokens.is_empty() {
                        self.macros.exported = ExportConfig::all_but();
                    } else {
                        let exported = if line_tokens.contains_text("=") {
                            // that's an assignment!
                            self.read_macro(line_tokens, line_number)?
                        } else {
                            self.expand_macros(&line_tokens)?
                        };
                        self.macros.exported.add_all(exported.split_whitespace());
                    }
                }
                #[cfg(feature = "full")]
                LineType::Unexport => {
                    let mut line_tokens = line_tokens;
                    line_tokens.strip_prefix("unexport");
                    if line_tokens.is_empty() {
                        self.macros.exported = ExportConfig::only();
                    } else {
                        let exported = self.expand_macros(&line_tokens)?;
                        self.macros.exported.remove_all(exported.split_whitespace());
                    }
                }
                LineType::Unknown => {
                    if !line_tokens.is_empty() {
                        bail!(
                            "error: line {}: unknown line \"{}\"",
                            line_number,
                            line_tokens
                        );
                    }
                }
            }
        }

        Ok(())
    }

    fn next_line(&mut self, settings: NextLineSettings) -> Option<(usize, Result<String>)> {
        lazy_static! {
            static ref COMMENT: Regex = #[allow(clippy::unwrap_used)]
            Regex::new(r"(^|[^\\])#.*$").unwrap();
        }
        let escaped_newline_replacement = settings.escaped_newline_replacement;
        if let Some((line_number, line)) = self.pending_line.take() {
            if settings.peeking {
                self.pending_line = Some((line_number, line.clone()));
            }
            let line = line.join(escaped_newline_replacement);
            let line = if settings.strip_comments {
                // TODO only do this if we were in don't-strip-comments mode before
                // TODO deduplicate
                COMMENT
                    .replace(&line, "$1")
                    .replace(r"\#", "#")
                    .trim_end()
                    .to_owned()
            } else {
                line
            };
            return Some((line_number, Ok(line)));
        }
        while let Some((line_number, line)) = self.lines_iter.next() {
            let line = match line {
                Ok(x) => x,
                Err(err) => return Some((line_number, Err(err))),
            };
            let line_without_comments = COMMENT.replace(&line, "$1").replace(r"\#", "#");
            let line_without_comments = line_without_comments.trim_end();
            // handle comments
            let line = if settings.strip_comments {
                line_without_comments.to_owned()
            } else {
                line
            };

            // handle escaped newlines
            let mut line_pieces = vec![line];
            while line_pieces.last().map_or(false, |p| p.ends_with('\\')) {
                line_pieces.last_mut().map(|x| x.pop());
                if let Some((n, x)) = self.lines_iter.next() {
                    let line = match x {
                        Ok(x) => x,
                        Err(err) => return Some((n, Err(err))),
                    };
                    let line = if settings.strip_comments {
                        COMMENT
                            .replace(&line, "$1")
                            .replace(r"\#", "#")
                            .trim_end()
                            .to_owned()
                    } else {
                        line
                    };
                    line_pieces.push(line.trim_start().to_owned());
                }
            }
            let line = line_pieces.join(escaped_newline_replacement);

            #[cfg(feature = "full")]
            {
                let cond_line =
                    ConditionalLine::from(line_without_comments, |t| self.expand_macros(t));
                let cond_line = match cond_line {
                    Ok(x) => x,
                    Err(err) => return Some((line_number, Err(err))),
                };
                if let Some(line) = cond_line {
                    let mut deferred_eval_context = DeferredEvalContext::new(self);
                    let action = line
                        .action(
                            self.conditional_stack.last(),
                            |name| self.macros.is_defined(name),
                            |t| self.expand_macros_deferred_eval(t, &mut deferred_eval_context),
                        )
                        .wrap_err_with(|| {
                            format!("while applying conditional on line {}", line_number)
                        });
                    for child in deferred_eval_context {
                        self.extend(child);
                    }
                    let action = match action {
                        Ok(x) => x,
                        Err(err) => return Some((line_number, Err(err))),
                    };
                    action.apply_to(&mut self.conditional_stack);
                    continue;
                }

                // skip lines if we need to
                if self
                    .conditional_stack
                    .iter()
                    .any(ConditionalState::skipping)
                {
                    continue;
                }
            }

            if settings.peeking {
                self.pending_line = Some((line_number, line_pieces));
            }
            return Some((line_number, Ok(line)));
        }
        None
    }

    /// Only applies the predicate to the next physical line in the file.
    /// Doesn't apply the escaped newline replacement unless the predicate passes.
    fn next_line_if(
        &mut self,
        settings: NextLineSettings,
        predicate: impl FnOnce(&(usize, Result<String>)) -> bool,
    ) -> Option<(usize, Result<String>)> {
        let peek_settings = NextLineSettings {
            peeking: true,
            ..settings
        };
        if predicate(&self.next_line(peek_settings)?) {
            self.next_line(settings)
        } else {
            None
        }
    }

    fn special_target_has_prereq(&self, target: &str, name: &str, empty_counts: bool) -> bool {
        self.targets
            .get(target)
            .or_else(|| self.built_in_targets.get(target))
            .map_or(false, |target| {
                (empty_counts && target.prerequisites.is_empty())
                    || target.prerequisites.iter().any(|e| e == name)
            })
    }

    fn read_include(&mut self, mut line_tokens: TokenString, line_number: usize) -> Result<()> {
        let suppress_errors = line_tokens.starts_with("-");
        line_tokens.strip_prefix("-");
        line_tokens.strip_prefix("include ");
        // remove extra leading space
        line_tokens.trim_start();
        let line = self.expand_macros(&line_tokens)?;
        let fields = line.split_whitespace();
        // POSIX says we only have to handle a single filename, but GNU make
        // handles arbitrarily many filenames, and it's not like that's more work
        for field in fields {
            log::trace!("{}:{}: including {}", &self.file_name, line_number, field);
            let child_stack = self.stack.with_scope(&self.macros);
            let child = MakefileReader::read_file(
                self.args,
                child_stack,
                field,
                Rc::clone(&self.file_names),
            )
            .with_context(|| format!("while including {}", field));
            match child {
                Ok(child) => {
                    let child = child.finish();
                    self.extend(child);
                }
                Err(err) => {
                    if !suppress_errors {
                        match err.downcast_ref::<IoError>() {
                            Some(err) if err.kind() == IoErrorKind::NotFound => {
                                log::error!(
                                    "{}:{}: included makefile {} not found",
                                    &self.file_name,
                                    line_number,
                                    field,
                                );
                                self.failed_includes.push(field.to_owned());
                            }
                            _ => {
                                return Err(err);
                            }
                        }
                    }
                }
            }
        }
        Ok(())
    }

    fn read_rule(&mut self, line_tokens: TokenString, line_number: usize) -> Result<()> {
        let (targets, not_targets) = line_tokens
            .split_once(":")
            .ok_or_else(|| eyre!("read_rule couldn't find a ':' on line {}", line_number))?;
        #[cfg(feature = "full")]
        let (static_targets, targets, not_targets) = if not_targets.contains_text(":") {
            // ugh, this is probably a Static Pattern Rule
            let (pattern, not_targets) = not_targets
                .split_once(":")
                .ok_or_else(|| eyre!("bro hold the fuck up it literally just had that"))?;
            (Some(targets), pattern, not_targets)
        } else {
            (None, targets, not_targets)
        };
        let targets = self.expand_macros(&targets)?;
        let targets = targets.split_whitespace().collect::<Vec<_>>();
        let (prerequisites, mut commands) = match not_targets.split_once(";") {
            Some((prerequisites, command)) => {
                // TODO make sure escaped newlines get retroactively treated correctly here
                (prerequisites, vec![command])
            }
            None => (not_targets, vec![]),
        };
        if prerequisites.contains_text("=") {
            log::error!("rule-specific macros are not implemented yet");
            return Ok(());
        }
        #[cfg(feature = "full")]
        let mut deferred_eval_context = DeferredEvalContext::new(self);
        let prerequisites = self
            .stack
            .with_scope(&self.macros)
            .with_scope(&LookupInternal::new_partial(&targets))
            .expand(
                &prerequisites,
                #[cfg(feature = "full")]
                Some(&mut deferred_eval_context),
            )?;
        #[cfg(feature = "full")]
        for child in deferred_eval_context {
            self.extend(child);
        }
        let prerequisites = prerequisites
            .split_whitespace()
            .map(|x| x.into())
            .collect::<Vec<String>>();

        let settings = NextLineSettings {
            escaped_newline_replacement: "\\\n",
            strip_comments: false,
            ..Default::default()
        };
        while let Some((_, x)) = self.next_line_if(settings, |(_, x)| {
            x.as_ref()
                .ok()
                .map_or(false, |line| line.starts_with('\t') || line.is_empty())
        }) {
            let mut line = x?;
            if !line.is_empty() {
                assert!(line.starts_with('\t'));
                line.remove(0);
            }
            if line.is_empty() {
                continue;
            }
            commands.push(
                line.parse()
                    .with_context(|| format!("failed to parse line {}", line_number))?,
            );
        }

        let commands = commands
            .into_iter()
            .map(CommandLine::from)
            .collect::<Vec<_>>();

        if targets.is_empty() {
            return Ok(());
        }

        // we don't know yet if it's a target rule or an inference rule (or a GNUish "pattern rule")
        let inference_match = inference_match(&targets, &prerequisites);
        #[cfg(feature = "full")]
        let is_pattern = targets.iter().all(|x| x.contains('%'));

        #[cfg(feature = "full")]
        if is_pattern {
            let new_rule = InferenceRule {
                source: ItemSource::File {
                    name: self.file_name.clone(),
                    line: line_number,
                },
                products: targets.into_iter().map(|x| x.to_owned()).collect(),
                prerequisites,
                commands,
            };

            if let Some(static_targets) = static_targets {
                let static_targets = self.expand_macros(&static_targets)?;
                let static_targets = static_targets.split_whitespace();
                for real_target in static_targets {
                    if new_rule.matches(real_target)? {
                        let new_target = Target {
                            name: real_target.to_owned(),
                            prerequisites: new_rule.prereqs(real_target)?.collect(),
                            commands: new_rule.commands.clone(),
                            stem: new_rule
                                .first_match(real_target)?
                                .and_then(|x| x.get(1).map(|x| x.as_str().to_owned())),
                            already_updated: Cell::new(false),
                        };
                        self.targets.put(new_target);
                    }
                }
            } else {
                self.inference_rules.push(new_rule);
            }
            return Ok(());
        }

        // don't interpret things like `.tmp: ; mkdir -p $@` as single-suffix rules
        let inference_match = inference_match.and_then(|inference| {
            if self.special_target_has_prereq(".SUFFIXES", inference.s1, false)
                && (inference.s2.is_empty()
                    || self.special_target_has_prereq(".SUFFIXES", inference.s2, false))
            {
                Some(inference)
            } else {
                log::info!(
                    "{}:{}: looks like {:?} is not a suffix rule because .SUFFIXES is {:?}",
                    &self.file_name,
                    line_number,
                    inference,
                    self.targets
                        .get(".SUFFIXES")
                        .or_else(|| self.built_in_targets.get(".SUFFIXES"))
                        .map(|x| &x.prerequisites)
                );
                None
            }
        });

        if let Some(inference_match) = inference_match {
            let new_rule = InferenceRule::new_suffix(
                ItemSource::File {
                    name: self.file_name.clone(),
                    line: line_number,
                },
                inference_match.s1.to_owned(),
                inference_match.s2.to_owned(),
                commands,
            );
            log::trace!(
                "suffix-based inference rule defined by {:?} - {:?}",
                &inference_match,
                &new_rule,
            );

            self.inference_rules.retain(|existing_rule| {
                (&existing_rule.prerequisites, &existing_rule.products)
                    != (&new_rule.prerequisites, &new_rule.products)
            });
            self.inference_rules.push(new_rule);
        } else {
            log::trace!(
                "{}:{}: new target {:?} based on {:?}",
                &self.file_name,
                line_number,
                &targets,
                &prerequisites
            );
            for target in targets {
                if self.first_non_special_target.is_none() && !target.starts_with('.') {
                    self.first_non_special_target = Some(target.into());
                }
                // TODO handle appending to built-in (it's Complicated)
                let new_target = Target {
                    name: target.into(),
                    prerequisites: prerequisites.clone(),
                    commands: commands.clone(),
                    stem: None,
                    already_updated: Cell::new(false),
                };
                self.targets.put(new_target);
            }
        }

        Ok(())
    }

    /// If successful, returns the name of the macro which was read.
    fn read_macro(&mut self, mut line_tokens: TokenString, line_number: usize) -> Result<String> {
        let (name, mut value) = if cfg!(feature = "full") && line_tokens.starts_with("define ") {
            line_tokens.strip_prefix("define ");
            if line_tokens.ends_with("=") {
                line_tokens.strip_suffix("=");
                line_tokens.trim_end();
            }
            let mut value = TokenString::empty();
            // TODO what should be done with escaped newlines
            let settings = NextLineSettings {
                strip_comments: false, // apparently
                ..Default::default()
            };
            while let Some((_, line)) = self.next_line(settings) {
                let line = line?;
                if line == "endef" {
                    break;
                }
                if !value.is_empty() {
                    value.extend(TokenString::text("\n"));
                }
                value.extend(line.parse()?);
            }
            (line_tokens, value)
        } else {
            line_tokens
                .split_once("=")
                .ok_or_else(|| eyre!("read_macro couldn't find a '=' on line {}", line_number))?
        };
        let name = self.expand_macros(&name)?;
        // GNUisms are annoying, but popular
        let mut expand_value = false;
        let mut skip_if_defined = false;
        let mut append = false;

        #[cfg(feature = "full")]
        let name = if let Some(real_name) = name.strip_suffix("::") {
            expand_value = true;
            real_name
        } else if let Some(real_name) = name.strip_suffix(":") {
            expand_value = true;
            real_name
        } else if let Some(real_name) = name.strip_suffix("?") {
            skip_if_defined = true;
            real_name
        } else if let Some(real_name) = name.strip_suffix("+") {
            append = true;
            real_name
        } else {
            &name
        };

        let name = name.trim();
        value.trim_start();

        let value = if expand_value {
            TokenString::text(
                self.expand_macros(&value)
                    .wrap_err_with(|| format!("while defining {} on line {}", name, line_number))?,
            )
        } else {
            value
        };

        let skipped = match self.macros.get(name) {
            // We always let command line or MAKEFLAGS macros override macros from the file.
            Some(Macro {
                source: ItemSource::CommandLineOrMakeflags,
                ..
            }) => true,
            // We let environment variables override macros from the file only if the command-line argument to do that was given
            Some(Macro {
                source: ItemSource::Environment,
                ..
            }) => self.args.environment_overrides,
            Some(_) => skip_if_defined,
            None => false,
        };
        if skipped {
            return Ok(name.to_owned());
        }

        log::trace!(
            "{}:{}: setting macro {} to {}",
            &self.file_name,
            line_number,
            name,
            &value
        );

        let value = match self.macros.pop(name) {
            Some(mut old_value) if append => {
                #[cfg(feature = "full")]
                let value = if old_value.eagerly_expanded {
                    TokenString::text(self.expand_macros(&value).wrap_err_with(|| {
                        format!("while defining {} on line {}", name, line_number)
                    })?)
                } else {
                    value
                };
                old_value.text.extend(TokenString::text(" "));
                old_value.text.extend(value);
                old_value
            }
            _ => Macro {
                source: ItemSource::File {
                    name: self.file_name.clone(),
                    line: line_number,
                },
                text: value,
                #[cfg(feature = "full")]
                eagerly_expanded: expand_value,
            },
        };
        self.macros.set(name.into(), value);

        Ok(name.to_owned())
    }

    fn expand_macros(&mut self, text: &TokenString) -> Result<String> {
        #[cfg(feature = "full")]
        let mut deferred_eval_context = DeferredEvalContext::new(self);
        let result = self.expand_macros_deferred_eval(
            text,
            #[cfg(feature = "full")]
            &mut deferred_eval_context,
        );
        #[cfg(feature = "full")]
        for child in deferred_eval_context {
            self.extend(child);
        }
        result
    }

    fn expand_macros_deferred_eval(
        &self,
        text: &TokenString,
        #[cfg(feature = "full")] deferred_eval_context: &mut DeferredEvalContext<R>,
    ) -> Result<String> {
        self.stack
            .with_scope(&self.macros)
            .expand(
                text,
                #[cfg(feature = "full")]
                Some(deferred_eval_context),
            )
            .wrap_err_with(|| format!("while expanding \"{}\"", text))
    }

    pub fn finish(self) -> FinishedMakefileReader {
        FinishedMakefileReader {
            inference_rules: self.inference_rules,
            macros: self.macros.data,
            #[cfg(feature = "full")]
            macro_exports: self.macros.exported,
            targets: self.targets.into(),
            first_non_special_target: self.first_non_special_target,
            failed_includes: self.failed_includes,
        }
    }

    fn extend(&mut self, new: FinishedMakefileReader) {
        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;
        }
        self.failed_includes.extend(new.failed_includes);
    }
}

pub struct FinishedMakefileReader {
    pub inference_rules: Vec<InferenceRule>,
    pub macros: HashMap<String, Macro>,
    #[cfg(feature = "full")]
    pub macro_exports: ExportConfig,
    pub targets: HashMap<String, Target>,
    pub first_non_special_target: Option<String>,
    pub failed_includes: Vec<String>,
}

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

    use std::io::Cursor;

    type R = Result<()>;

    #[test]
    fn multi_line_dependencies() -> R {
        let file = "
unrelated: example
\tswag
x = 3 4 \\
\t\t5
a: $(x) b \\
\t\tc \\
\t\td
\tfoo";
        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?
        .finish();
        assert_eq!(
            makefile.targets["a"].prerequisites,
            vec!["3", "4", "5", "b", "c", "d"]
        );
        Ok(())
    }

    #[cfg(feature = "full")]
    #[test]
    fn basic_conditionals() -> R {
        let file = "
ifeq (1,1)
worked = yes
else ifeq (2,2)
worked = no
else 
worked = perhaps
endif
        ";
        let args = Args::empty();
        let mut makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        assert_eq!(
            makefile.expand_macros(&TokenString::r#macro("worked"))?,
            "yes"
        );
        Ok(())
    }

    #[cfg(feature = "full")]
    #[test]
    fn condition_in_rule() -> R {
        let file = "
a:
ifeq (1,1)
\tfoo
endif
        ";
        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        let makefile = makefile.finish();
        assert_eq!(makefile.targets["a"].commands.len(), 1);
        Ok(())
    }

    #[cfg(feature = "full")]
    #[test]
    fn define_syntax() -> R {
        let file = "
define foo =
bar
baz
endef
        ";
        let args = Args::empty();
        let mut makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        assert_eq!(
            makefile.expand_macros(&TokenString::r#macro("foo"))?,
            "bar\nbaz"
        );
        Ok(())
    }

    #[cfg(feature = "full")]
    #[test]
    fn elseif() -> R {
        let file = "
ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
    KBUILD_CFLAGS += -O2
else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3
    KBUILD_CFLAGS += -O3
else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
    KBUILD_CFLAGS += -Os
endif
FOO = bar
";
        let args = Args::empty();
        let mut makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        assert_eq!(makefile.expand_macros(&TokenString::r#macro("FOO"))?, "bar",);
        Ok(())
    }

    #[test]
    #[cfg(feature = "full")]
    fn eval() -> R {
        // This, for the record, is a terrible misfeature.
        // If you need this, you probably shouldn't be using Make.
        // But a lot of people are using this and still use Make anyway, so here we go,
        // I guess.

        let file = "
PROGRAMS    = server client

server_OBJS = server.o server_priv.o server_access.o
server_LIBS = priv protocol

client_OBJS = client.o client_api.o client_mem.o
client_LIBS = protocol

# Everything after this is generic

.PHONY: all
all: $(PROGRAMS)

define PROGRAM_template =
 $(1): $$($(1)_OBJS) $$($(1)_LIBS:%=-l%)
 ALL_OBJS   += $$($(1)_OBJS)
endef

$(foreach prog,$(PROGRAMS),$(eval $(call PROGRAM_template,$(prog))))

$(PROGRAMS):
\t$(LINK.o) $^ $(LDLIBS) -o $@

clean:
\trm -f $(ALL_OBJS) $(PROGRAMS)
        ";

        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        let makefile = makefile.finish();
        assert!(makefile.targets.contains_key("server"));
        Ok(())
    }

    #[test]
    fn comment_bullshit() -> R {
        let file = "
foo: bar baz#swag
example: test\\#post
info:
\thello # there
";
        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        let makefile = makefile.finish();
        assert_eq!(
            makefile.targets["foo"],
            Target {
                name: "foo".to_owned(),
                prerequisites: vec!["bar".to_owned(), "baz".to_owned()],
                commands: vec![],
                stem: None,
                already_updated: Cell::new(false)
            }
        );
        assert_eq!(
            makefile.targets["example"],
            Target {
                name: "example".to_owned(),
                prerequisites: vec!["test#post".to_owned()],
                commands: vec![],
                stem: None,
                already_updated: Cell::new(false)
            }
        );
        assert_eq!(
            makefile.targets["info"],
            Target {
                name: "info".to_owned(),
                prerequisites: vec![],
                commands: vec![CommandLine::from(TokenString::text("hello # there")),],
                stem: None,
                already_updated: Cell::new(false)
            }
        );

        Ok(())
    }

    #[test]
    fn sdafjijsafjdoisdf() -> R {
        let file = "
cursed:
\techo this uses the bash variable '$$#' and all that \\
\techo yeah its value is $$# and it's really cool
";
        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        let _makefile = makefile.finish();
        Ok(())
    }

    #[test]
    fn double_suffix_rule() -> R {
        let file = "
.c.o:
\techo yeet
.SUFFIXES:
.l.a:
\techo hey
.SUFFIXES: .test .post
.post.test:
\techo hiiii
";
        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        let makefile = makefile.finish();
        assert_eq!(makefile.inference_rules.len(), 2);
        Ok(())
    }

    #[test]
    fn dependency_prepending_appending() -> R {
        let file = "
test: b
test: a
\techo hi
test: c
        ";
        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        let makefile = makefile.finish();
        assert_eq!(
            makefile.targets["test"].prerequisites,
            vec!["a".to_owned(), "b".to_owned(), "c".to_owned()]
        );
        Ok(())
    }

    #[cfg(feature = "full")]
    #[test]
    fn export_assign() -> R {
        let file = "export x = 3";
        let args = Args::empty();
        let makefile = MakefileReader::read(
            &args,
            MacroScopeStack::default(),
            MacroSet::new(),
            Cursor::new(file),
            "",
            Default::default(),
        )?;
        let makefile = makefile.finish();
        assert_eq!(
            makefile.macros.get("x").map(|x| &x.text),
            Some(&TokenString::text("3"))
        );
        assert!(
            matches!(makefile.macro_exports, ExportConfig::Only(exported) if exported.contains("x"))
        );
        Ok(())
    }
}