add (& somewhat test!) GNUful conditionals

3 files changed, 239 insertions, 0 deletions

diff --git a/src/makefile/conditional.rs b/src/makefile/conditional.rs
new file mode 100644
index 0000000..f9d2d60
--- /dev/null
+++ b/src/makefile/conditional.rs
@@ -0,0 +1,164 @@
+use super::token::TokenString;
+
+pub(crate) enum ConditionalLine {
+    /// spelled "ifeq"
+    IfEqual(TokenString, TokenString),
+    /// spelled "ifneq"
+    IfNotEqual(TokenString, TokenString),
+    /// spelled "ifdef"
+    IfDefined(String),
+    /// spelled "ifndef"
+    IfNotDefined(String),
+    /// spelled "else"
+    Else,
+    /// spelled "else condition"
+    ElseIf(Box<ConditionalLine>),
+    /// spelled "endif"
+    EndIf,
+}
+
+pub(crate) enum ConditionalState {
+    /// we saw a conditional, the condition was true, we're executing now
+    /// and if we hit an else we will start SkippingUntilEndIf
+    Executing,
+    /// we saw a conditional, the condition was false, we're ignoring now
+    /// and if we hit an else we'll start executing
+    /// (or if it's an else if we'll check the condition)
+    SkippingUntilElseOrEndIf,
+    /// we saw a conditional, the condition was true, we executed, and now we hit an else
+    /// so we don't need to stop and evaluate new conditions, because we straight up do
+    /// not care
+    SkippingUntilEndIf,
+}
+
+impl ConditionalState {
+    pub(crate) const fn skipping(&self) -> bool {
+        match self {
+            Self::Executing => false,
+            Self::SkippingUntilElseOrEndIf | Self::SkippingUntilEndIf => true,
+        }
+    }
+}
+
+pub(crate) enum ConditionalStateAction {
+    Push(ConditionalState),
+    Replace(ConditionalState),
+    Pop,
+}
+
+impl ConditionalStateAction {
+    pub(crate) fn apply_to(self, stack: &mut Vec<ConditionalState>) {
+        match self {
+            Self::Push(state) => stack.push(state),
+            Self::Replace(state) => match stack.last_mut() {
+                Some(x) => *x = state,
+                None => panic!("applying Replace on an empty condition stack"),
+            },
+            Self::Pop => {
+                stack.pop();
+            }
+        }
+    }
+}
+
+fn decode_condition_args(line_body: &str) -> Option<(TokenString, TokenString)> {
+    let tokens: TokenString = line_body.parse().ok()?;
+    let (mut arg1, mut arg2) = if tokens.starts_with("(") && tokens.ends_with(")") {
+        let mut tokens = tokens;
+        tokens.strip_prefix("(");
+        tokens.strip_suffix(")");
+        tokens.split_once(',')?
+    } else {
+        // TODO see if i really need to implement potentially-mixed-quoted args
+        return None;
+    };
+    arg1.trim_end();
+    arg2.trim_start();
+    Some((arg1, arg2))
+}
+
+impl ConditionalLine {
+    pub(crate) fn from(line: &str, expand_macro: impl Fn(&TokenString) -> String) -> Option<Self> {
+        if let Some(line) = line.strip_prefix("ifeq ") {
+            let (arg1, arg2) = decode_condition_args(line)?;
+            Some(Self::IfEqual(arg1, arg2))
+        } else if let Some(line) = line.strip_prefix("ifneq ") {
+            let (arg1, arg2) = decode_condition_args(line)?;
+            Some(Self::IfNotEqual(arg1, arg2))
+        } else if let Some(line) = line.strip_prefix("ifdef ") {
+            Some(Self::IfDefined(expand_macro(&line.parse().ok()?)))
+        } else if let Some(line) = line.strip_prefix("ifndef ") {
+            Some(Self::IfNotDefined(expand_macro(&line.parse().ok()?)))
+        } else if line == "else" {
+            Some(Self::Else)
+        } else if let Some(line) = line.strip_prefix("else ") {
+            let sub_condition = Self::from(line, expand_macro)?;
+            Some(Self::ElseIf(Box::new(sub_condition)))
+        } else if line == "endif" {
+            Some(Self::EndIf)
+        } else {
+            None
+        }
+    }
+
+    pub(crate) fn action(
+        &self,
+        current_state: Option<&ConditionalState>,
+        is_macro_defined: impl Fn(&str) -> bool,
+        expand_macro: impl Fn(&TokenString) -> String,
+    ) -> ConditionalStateAction {
+        use ConditionalState as State;
+        use ConditionalStateAction as Action;
+        match self {
+            Self::IfEqual(arg1, arg2) => {
+                let arg1 = expand_macro(arg1);
+                let arg2 = expand_macro(arg2);
+                if arg1 == arg2 {
+                    Action::Push(State::Executing)
+                } else {
+                    Action::Push(State::SkippingUntilElseOrEndIf)
+                }
+            }
+            Self::IfNotEqual(arg1, arg2) => {
+                let arg1 = expand_macro(arg1);
+                let arg2 = expand_macro(arg2);
+                if arg1 == arg2 {
+                    Action::Push(State::SkippingUntilElseOrEndIf)
+                } else {
+                    Action::Push(State::Executing)
+                }
+            }
+            Self::IfDefined(name) => {
+                if is_macro_defined(name) {
+                    Action::Push(State::Executing)
+                } else {
+                    Action::Push(State::SkippingUntilElseOrEndIf)
+                }
+            }
+            Self::IfNotDefined(name) => {
+                if is_macro_defined(name) {
+                    Action::Push(State::SkippingUntilElseOrEndIf)
+                } else {
+                    Action::Push(State::Executing)
+                }
+            }
+            Self::Else => Action::Replace(match current_state {
+                Some(State::Executing) | Some(State::SkippingUntilEndIf) => {
+                    State::SkippingUntilEndIf
+                }
+                Some(State::SkippingUntilElseOrEndIf) => State::Executing,
+                None => panic!("got an Else but not in a conditional"),
+            }),
+            Self::ElseIf(inner_condition) => match current_state {
+                Some(State::Executing) | Some(State::SkippingUntilEndIf) => {
+                    Action::Replace(State::SkippingUntilEndIf)
+                }
+                Some(State::SkippingUntilElseOrEndIf) => {
+                    inner_condition.action(current_state, is_macro_defined, expand_macro)
+                }
+                None => panic!("got an ElseIf but not in a conditional"),
+            },
+            Self::EndIf => Action::Pop,
+        }
+    }
+}
diff --git a/src/makefile/mod.rs b/src/makefile/mod.rs
index 2f73c70..0d4cded 100644
--- a/src/makefile/mod.rs
+++ b/src/makefile/mod.rs
@@ -13,11 +13,13 @@ use regex::Regex;
 use crate::args::Args;
 
 mod command_line;
+mod conditional;
 mod inference_rules;
 mod target;
 mod token;
 
 use command_line::CommandLine;
+use conditional::{ConditionalLine, ConditionalState};
 use inference_rules::InferenceRule;
 use target::Target;
 use token::{tokenize, Token, TokenString};
@@ -151,6 +153,7 @@ impl<'a> Makefile<'a> {
 
     pub(crate) fn and_read(&mut self, source: impl BufRead) {
         let mut lines_iter = source.lines().enumerate().peekable();
+        let mut conditional_stack: Vec<ConditionalState> = vec![];
         while let Some((line_number, line)) = lines_iter.next() {
             // TODO handle I/O errors at all
             let mut line = line.expect("failed to read line of makefile!");
@@ -170,6 +173,14 @@ impl<'a> Makefile<'a> {
             }
             let line = COMMENT.replace(&line, "").into_owned();
 
+            // skip lines if we need to
+            if conditional_stack
+                .last()
+                .map_or(false, ConditionalState::skipping)
+            {
+                continue;
+            }
+
             // handle include lines
             if let Some(line) = line.strip_prefix("include ") {
                 // remove extra leading space
@@ -181,6 +192,14 @@ impl<'a> Makefile<'a> {
                 for field in fields {
                     self.and_read_file(field);
                 }
+            } else if let Some(line) = ConditionalLine::from(&line, |t| self.expand_macros(t, None))
+            {
+                line.action(
+                    conditional_stack.last(),
+                    |name| self.macros.contains_key(name),
+                    |t| self.expand_macros(t, None),
+                )
+                .apply_to(&mut conditional_stack);
             } else if line.trim().is_empty() {
                 // handle blank lines
                 continue;
@@ -728,3 +747,38 @@ fn builtin_targets() -> Vec<Target> {
         already_updated: Cell::new(false),
     }]
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    use std::io::Cursor;
+
+    fn empty_makefile(args: &Args) -> Makefile {
+        Makefile {
+            inference_rules: vec![],
+            macros: HashMap::new(),
+            targets: RefCell::new(HashMap::new()),
+            first_non_special_target: None,
+            args,
+        }
+    }
+
+    #[test]
+    fn basic_conditionals() {
+        let file = "
+ifeq (1,1)
+worked = yes
+else ifeq (2,2)
+worked = no
+endif
+        ";
+        let args = Args::empty();
+        let mut makefile = empty_makefile(&args);
+        makefile.and_read(Cursor::new(file));
+        assert_eq!(
+            makefile.expand_macros(&"$(worked)".parse().unwrap(), None),
+            "yes"
+        );
+    }
+}
diff --git a/src/makefile/token.rs b/src/makefile/token.rs
index 811f30f..86c442b 100644
--- a/src/makefile/token.rs
+++ b/src/makefile/token.rs
@@ -47,6 +47,13 @@ impl TokenString {
         None
     }
 
+    pub(crate) fn starts_with(&self, pattern: &str) -> bool {
+        match self.0.first() {
+            Some(Token::Text(t)) => t.starts_with(pattern),
+            _ => false,
+        }
+    }
+
     pub(crate) fn ends_with(&self, pattern: &str) -> bool {
         match self.0.last() {
             Some(Token::Text(t)) => t.ends_with(pattern),
@@ -54,6 +61,14 @@ impl TokenString {
         }
     }
 
+    pub(crate) fn strip_prefix(&mut self, suffix: &str) {
+        if let Some(Token::Text(t)) = self.0.first_mut() {
+            if let Some(x) = t.strip_prefix(suffix) {
+                *t = x.into()
+            }
+        }
+    }
+
     pub(crate) fn strip_suffix(&mut self, suffix: &str) {
         if let Some(Token::Text(t)) = self.0.last_mut() {
             if let Some(x) = t.strip_suffix(suffix) {
@@ -71,6 +86,12 @@ impl TokenString {
             *t = t.trim_start().into();
         }
     }
+
+    pub(crate) fn trim_end(&mut self) {
+        if let Some(Token::Text(t)) = self.0.last_mut() {
+            *t = t.trim_end().into();
+        }
+    }
 }
 
 impl fmt::Display for TokenString {