srcmetrics 0.2.0

//! Helpers shared by calculators. IR-only.

use crate::ir::{File, Node, NodeKind, TokenKind};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum LineClass {
    Code,
    Comment,
    Blank,
}

/// Classifies every line of the file (index 0 = line 1).
///
/// A line is `Code` if any non-comment token occupies it, else `Comment` if a comment token
/// occupies it, else `Blank` if it is whitespace only. A non-blank line occupied by no token
/// means the IR is inconsistent with the source, which is reported instead of guessed.
pub(crate) fn line_classes(file: &File) -> Result<Vec<LineClass>, String> {
    let source_lines: Vec<&str> = file.source.lines().collect();
    let mut classes: Vec<Option<LineClass>> = vec![None; source_lines.len()];
    for token in &file.tokens {
        let class = if token.kind == TokenKind::Comment {
            LineClass::Comment
        } else {
            LineClass::Code
        };
        for line in token.range.first_line()..=token.range.last_line() {
            let slot = classes.get_mut(line - 1).ok_or_else(|| {
                format!(
                    "token {:?} is on line {line}, beyond the end of the source",
                    token.text
                )
            })?;
            if *slot != Some(LineClass::Code) {
                *slot = Some(class);
            }
        }
    }
    classes
        .into_iter()
        .zip(&source_lines)
        .enumerate()
        .map(|(i, (class, text))| match class {
            Some(c) => Ok(c),
            None if text.trim().is_empty() => Ok(LineClass::Blank),
            None => Err(format!("line {} has text that no token covers", i + 1)),
        })
        .collect()
}

/// Statement-like node kinds (size.statement_count).
pub(crate) fn is_statement(kind: NodeKind) -> bool {
    use NodeKind::*;
    matches!(
        kind,
        Statement | Declaration | Branch | Loop | Return | Jump
    )
}

/// Decision points of Cyclomatic Complexity.
pub(crate) fn is_decision(kind: NodeKind) -> bool {
    use NodeKind::*;
    matches!(kind, Branch | Loop | Case | Catch | Logical | Conditional)
}

/// Control structures that open a nesting level.
pub(crate) fn is_nesting(kind: NodeKind) -> bool {
    use NodeKind::*;
    matches!(kind, Branch | Loop | Case | Catch)
}

/// A branch continuing an if-chain (`else if`, `elif`): a branch whose parent is an `else`
/// or another branch. It is part of its chain head's level, not a deeper one.
pub(crate) fn is_continuation(file: &File, node: &Node) -> bool {
    node.kind == NodeKind::Branch
        && node
            .parent
            .is_some_and(|p| matches!(file.node(p).kind, NodeKind::Else | NodeKind::Branch))
}

/// Nesting level of every node (indexed by `NodeId`): the number of enclosing nodes for which
/// `opens_level` holds, counted within the node's function (levels restart inside nested functions).
/// A continuation branch (`else if`, `elif`) has the level of its chain head (ADR-0007).
///
/// One pass in arena order, which is pre-order (parents first), so deep trees such as long
/// `else if` ladders cost O(nodes) and no recursion.
pub(crate) fn nesting_levels(file: &File, opens_level: impl Fn(&Node) -> bool) -> Vec<usize> {
    let mut own = vec![0; file.nodes.len()];
    // Level of the children of each node.
    let mut inner = vec![0; file.nodes.len()];
    for node in &file.nodes {
        let i = node.id.0;
        own[i] = match node.parent {
            None => 0,
            Some(p) if is_continuation(file, node) => {
                // Same level as the branch this one continues (the parent, or the else's parent).
                let owner = if file.node(p).kind == NodeKind::Else {
                    file.node(p)
                        .parent
                        .expect("an else node always has a parent")
                } else {
                    p
                };
                own[owner.0]
            }
            Some(p) => inner[p.0],
        };
        inner[i] = if node.kind == NodeKind::Function {
            0
        } else {
            own[i] + usize::from(opens_level(node))
        };
    }
    own
}