repotoire 0.8.0

//! Intra-function heuristic data flow analysis for taint tracking.
//!
//! This module provides line-by-line scanning with variable propagation
//! for tracking how data flows from taint sources through variables to sinks
//! within a single function body.

use crate::detectors::taint::TaintCategory;
use crate::parsers::lightweight::Language;
use std::collections::{HashMap, HashSet};

// ---- Types ----------------------------------------------------------------

/// Result of intra-function data flow analysis.
#[derive(Debug, Clone)]
#[allow(dead_code)] // Fields used by tests and future callers for detailed flow inspection
pub struct IntraFlowResult {
    /// Variables that are tainted at each point (var name -> source it came from).
    pub tainted_vars: HashMap<String, TaintSource>,
    /// Detected flows from a tainted variable into a sink call.
    pub sink_reaches: Vec<SinkReach>,
    /// Variables that were sanitized (cleared of taint).
    pub sanitized_vars: HashSet<String>,
}

/// Where a tainted variable got its taint from.
#[derive(Debug, Clone)]
#[allow(dead_code)] // Fields used by tests and callers that inspect taint provenance
pub struct TaintSource {
    /// The source pattern that matched (e.g. "request.args").
    pub pattern: String,
    /// Line number where taint was introduced.
    pub line: usize,
}

/// A tainted variable reaching a dangerous sink.
#[derive(Debug, Clone)]
pub struct SinkReach {
    /// The tainted variable name.
    pub variable: String,
    /// Where the variable got tainted.
    pub taint_source: TaintSource,
    /// The sink function/pattern that was reached.
    pub sink_pattern: String,
    /// Line number where the sink is called.
    pub sink_line: usize,
    /// Whether a sanitizer was applied between source and sink.
    pub is_sanitized: bool,
    /// Confidence (0.0-1.0) based on how strong the evidence is.
    pub confidence: f64,
}

// ---- HeuristicFlow --------------------------------------------------------

/// Line-by-line heuristic data flow analysis.
///
/// Tracks variable taint through:
/// - Assignment from source patterns (`x = request.args.get(...)`)
/// - Propagation through assignment (`y = x`, `z = f"...{x}..."`)
/// - String concatenation/interpolation
/// - Sanitizer clearing (`clean = escape(x)`)
/// - Sink argument detection (`cursor.execute(query)`)
pub struct HeuristicFlow;

impl HeuristicFlow {
    pub fn new() -> Self {
        Self
    }

    /// Analyze data flow within a single function body.
    pub fn analyze_intra_function(
        &self,
        func_source: &str,
        language: Language,
        category: TaintCategory,
        sources: &HashSet<String>,
        sinks: &HashSet<String>,
        sanitizers: &HashSet<String>,
    ) -> IntraFlowResult {
        let _ = category; // Available for future category-specific logic

        // Pre-lowercase sources once: Vec<(original, lowered)> for source matching
        let sources_lower: Vec<(String, String)> = sources
            .iter()
            .map(|s| (s.clone(), s.to_lowercase()))
            .collect();

        // Pre-lowercase sinks once: Vec<(original, lowered)> for sink matching
        let sinks_lower: Vec<(String, String)> = sinks
            .iter()
            .map(|s| (s.clone(), s.to_lowercase()))
            .collect();

        // Pre-lowercase sanitizers once: Vec<String> (only need lowered form)
        let sanitizers_lower: Vec<String> = sanitizers.iter().map(|s| s.to_lowercase()).collect();

        let mut tainted: HashMap<String, TaintSource> = HashMap::new();
        let mut sanitized: HashSet<String> = HashSet::new();
        let mut sink_reaches: Vec<SinkReach> = Vec::new();

        for (line_idx, line) in func_source.lines().enumerate() {
            let line_num = line_idx + 1;
            let trimmed = line.trim();

            // Skip empty lines and comments
            if trimmed.is_empty()
                || trimmed.starts_with('#')
                || trimmed.starts_with("//")
                || trimmed.starts_with('*')
            {
                continue;
            }

            // Step 1: Check if this line introduces taint from a source
            if let Some((lhs, rhs)) = self.parse_assignment(line, language) {
                let rhs_lower = rhs.to_lowercase();

                // Check if RHS contains a taint source (using pre-lowercased sources)
                let matched_source = sources_lower
                    .iter()
                    .find(|(_, lowered)| rhs_lower.contains(lowered.as_str()));

                if let Some((original, _)) = matched_source {
                    tainted.insert(
                        lhs.to_string(),
                        TaintSource {
                            pattern: original.clone(),
                            line: line_num,
                        },
                    );
                    sanitized.remove(lhs);
                    continue;
                }

                // Step 2: Check if RHS references a tainted variable (propagation)
                if let Some(source_var) = self.rhs_references_tainted(rhs, &tainted) {
                    // But first check if RHS also calls a sanitizer
                    if self.is_sanitizer_call(rhs, &sanitizers_lower) {
                        sanitized.insert(lhs.to_string());
                    } else {
                        // Propagate taint
                        if let Some(source) = tainted.get(&source_var) {
                            tainted.insert(lhs.to_string(), source.clone());
                            sanitized.remove(lhs);
                        }
                    }
                    continue;
                }

                // Step 3: Check if LHS is being sanitized
                if self.is_sanitizer_call(rhs, &sanitizers_lower) && tainted.contains_key(lhs) {
                    sanitized.insert(lhs.to_string());
                    continue;
                }
            }

            // Step 4: Check if this line has a sink call with tainted arguments
            let mut reaches =
                self.check_sink_call(trimmed, line_num, &tainted, &sinks_lower, &sanitized);
            sink_reaches.append(&mut reaches);

            // Also check non-assignment lines that reference tainted vars in sink calls
            // e.g., `cursor.execute(query)` without assignment
        }

        IntraFlowResult {
            tainted_vars: tainted,
            sink_reaches,
            sanitized_vars: sanitized,
        }
    }

    /// Check if a line contains an assignment and extract (lhs, rhs).
    fn parse_assignment<'a>(&self, line: &'a str, lang: Language) -> Option<(&'a str, &'a str)> {
        // Skip comments
        let trimmed = line.trim();
        if trimmed.starts_with('#')
            || trimmed.starts_with("//")
            || trimmed.starts_with('*')
            || trimmed.starts_with("/*")
        {
            return None;
        }

        // Handle different assignment styles
        match lang {
            Language::Python => {
                // x = expr  (but not ==, !=, <=, >=)
                if let Some(eq_pos) = trimmed.find('=') {
                    if eq_pos > 0
                        && !trimmed[eq_pos..].starts_with("==")
                        && !matches!(
                            trimmed.as_bytes().get(eq_pos - 1),
                            Some(b'!' | b'<' | b'>' | b'=')
                        )
                    {
                        let lhs = trimmed[..eq_pos].trim();
                        let rhs = trimmed[eq_pos + 1..].trim();
                        // Must be a simple variable name (no dots, brackets on lhs for now)
                        if is_simple_var(lhs) && !rhs.is_empty() {
                            return Some((lhs, rhs));
                        }
                    }
                }
            }
            Language::JavaScript | Language::TypeScript => {
                // const/let/var x = expr  OR  x = expr
                let stripped = trimmed
                    .strip_prefix("const ")
                    .or_else(|| trimmed.strip_prefix("let "))
                    .or_else(|| trimmed.strip_prefix("var "))
                    .unwrap_or(trimmed);
                if let Some(eq_pos) = stripped.find('=') {
                    if eq_pos > 0
                        && !stripped[eq_pos..].starts_with("==")
                        && !stripped[eq_pos..].starts_with("=>")
                        && !matches!(
                            stripped.as_bytes().get(eq_pos - 1),
                            Some(b'!' | b'<' | b'>' | b'=')
                        )
                    {
                        let lhs = stripped[..eq_pos].trim();
                        // Handle type annotations: `x: string = ...`
                        let lhs = lhs.split(':').next().unwrap_or(lhs).trim();
                        let rhs = stripped[eq_pos + 1..].trim();
                        if is_simple_var(lhs) && !rhs.is_empty() {
                            return Some((lhs, rhs));
                        }
                    }
                }
            }
            Language::Go => {
                // x := expr  OR  x = expr
                if let Some(pos) = trimmed.find(":=") {
                    let lhs = trimmed[..pos].trim();
                    let rhs = trimmed[pos + 2..].trim();
                    let lhs = lhs.split(',').next().unwrap_or(lhs).trim();
                    if is_simple_var(lhs) && !rhs.is_empty() {
                        return Some((lhs, rhs));
                    }
                } else if let Some(eq_pos) = trimmed.find('=') {
                    if eq_pos > 0
                        && !trimmed[eq_pos..].starts_with("==")
                        && !matches!(
                            trimmed.as_bytes().get(eq_pos - 1),
                            Some(b'!' | b'<' | b'>' | b'=')
                        )
                    {
                        let lhs = trimmed[..eq_pos].trim();
                        let rhs = trimmed[eq_pos + 1..].trim();
                        if is_simple_var(lhs) && !rhs.is_empty() {
                            return Some((lhs, rhs));
                        }
                    }
                }
            }
            Language::Rust => {
                // let (mut) x = expr
                let stripped = trimmed
                    .strip_prefix("let ")
                    .map(|s| s.strip_prefix("mut ").unwrap_or(s));
                if let Some(stripped) = stripped {
                    if let Some(eq_pos) = stripped.find('=') {
                        if !stripped[eq_pos..].starts_with("==") {
                            let lhs = stripped[..eq_pos].trim();
                            // Handle type annotation: `x: Type = ...`
                            let lhs = lhs.split(':').next().unwrap_or(lhs).trim();
                            let rhs = stripped[eq_pos + 1..].trim();
                            if is_simple_var(lhs) && !rhs.is_empty() {
                                return Some((lhs, rhs));
                            }
                        }
                    }
                }
                // Also handle reassignment: x = expr
                if !trimmed.starts_with("let ") {
                    if let Some(eq_pos) = trimmed.find('=') {
                        if eq_pos > 0
                            && !trimmed[eq_pos..].starts_with("==")
                            && !trimmed[eq_pos..].starts_with("=>")
                            && !matches!(
                                trimmed.as_bytes().get(eq_pos - 1),
                                Some(b'!' | b'<' | b'>' | b'=')
                            )
                        {
                            let lhs = trimmed[..eq_pos].trim();
                            let rhs = trimmed[eq_pos + 1..].trim();
                            if is_simple_var(lhs) && !rhs.is_empty() {
                                return Some((lhs, rhs));
                            }
                        }
                    }
                }
            }
            Language::Java | Language::CSharp | Language::Kotlin => {
                // Type x = expr  OR  var x = expr  OR  x = expr
                // Simple heuristic: find `=` that isn't `==`
                if let Some(eq_pos) = trimmed.find('=') {
                    if eq_pos > 0
                        && !trimmed[eq_pos..].starts_with("==")
                        && !matches!(
                            trimmed.as_bytes().get(eq_pos - 1),
                            Some(b'!' | b'<' | b'>' | b'=')
                        )
                    {
                        let lhs_full = trimmed[..eq_pos].trim();
                        let rhs = trimmed[eq_pos + 1..].trim();
                        // Take the last word as the variable name
                        let lhs = lhs_full.split_whitespace().last().unwrap_or(lhs_full);
                        if is_simple_var(lhs) && !rhs.is_empty() {
                            return Some((lhs, rhs));
                        }
                    }
                }
            }
            _ => {
                // Generic: look for simple `x = expr`
                if let Some(eq_pos) = trimmed.find('=') {
                    if eq_pos > 0
                        && !trimmed[eq_pos..].starts_with("==")
                        && !matches!(
                            trimmed.as_bytes().get(eq_pos - 1),
                            Some(b'!' | b'<' | b'>' | b'=')
                        )
                    {
                        let lhs = trimmed[..eq_pos].trim();
                        let rhs = trimmed[eq_pos + 1..].trim();
                        if is_simple_var(lhs) && !rhs.is_empty() {
                            return Some((lhs, rhs));
                        }
                    }
                }
            }
        }

        None
    }

    /// Check if a right-hand side expression references any tainted variable.
    fn rhs_references_tainted(
        &self,
        rhs: &str,
        tainted: &HashMap<String, TaintSource>,
    ) -> Option<String> {
        for var in tainted.keys() {
            if rhs_contains_var(rhs, var) {
                return Some(var.clone());
            }
        }
        None
    }

    /// Check if a line calls a sanitizer on a tainted variable.
    ///
    /// `sanitizers_lower` must contain pre-lowercased sanitizer patterns.
    fn is_sanitizer_call(&self, rhs: &str, sanitizers_lower: &[String]) -> bool {
        let rhs_lower = rhs.to_lowercase();
        sanitizers_lower
            .iter()
            .any(|s| rhs_lower.contains(s.as_str()))
    }

    /// Check if a line calls a sink with a tainted argument.
    ///
    /// `sinks_lower` is a slice of `(original_name, lowercased_name)` pairs,
    /// pre-lowercased once at analysis start to avoid per-line allocations.
    fn check_sink_call(
        &self,
        line: &str,
        line_num: usize,
        tainted: &HashMap<String, TaintSource>,
        sinks_lower: &[(String, String)],
        sanitized: &HashSet<String>,
    ) -> Vec<SinkReach> {
        let line_lower = line.to_lowercase();

        // Early return: collect only sinks that appear in this line.
        // Most lines contain no sink at all, so this skips the tainted-var loop entirely.
        let matching_sinks: Vec<&(String, String)> = sinks_lower
            .iter()
            .filter(|(_, lowered)| line_lower.contains(lowered.as_str()))
            .collect();

        if matching_sinks.is_empty() {
            return Vec::new();
        }

        let mut reaches = Vec::new();

        for (original, lowered) in matching_sinks {
            // Check if any tainted variable appears as argument to this sink
            for (var, source) in tainted {
                if sanitized.contains(var) {
                    continue;
                }
                // Check if var appears in the arguments of the sink call
                if line_contains_var_in_call(line, lowered, var) {
                    reaches.push(SinkReach {
                        variable: var.clone(),
                        taint_source: source.clone(),
                        sink_pattern: original.clone(),
                        sink_line: line_num,
                        is_sanitized: false,
                        confidence: 0.85,
                    });
                }
            }
        }

        reaches
    }
}

// ---- Helpers ---------------------------------------------------------------

/// Check if a string is a simple variable name (no dots, brackets, etc.)
fn is_simple_var(s: &str) -> bool {
    !s.is_empty()
        && s.chars()
            .next()
            .is_some_and(|c| c.is_alphabetic() || c == '_')
        && s.chars().all(|c| c.is_alphanumeric() || c == '_')
}

/// Check if a RHS expression references a specific variable.
fn rhs_contains_var(rhs: &str, var: &str) -> bool {
    // Find all occurrences and check they're at word boundaries
    let mut search_from = 0;
    while let Some(pos) = rhs[search_from..].find(var) {
        let abs_pos = search_from + pos;
        let before_ok = abs_pos == 0
            || !rhs.as_bytes()[abs_pos - 1].is_ascii_alphanumeric()
                && rhs.as_bytes()[abs_pos - 1] != b'_';
        let after_pos = abs_pos + var.len();
        let after_ok = after_pos >= rhs.len()
            || !rhs.as_bytes()[after_pos].is_ascii_alphanumeric()
                && rhs.as_bytes()[after_pos] != b'_';

        if before_ok && after_ok {
            return true;
        }
        search_from = abs_pos + 1;
    }
    false
}

/// Check if a variable appears within a sink call's arguments on a line.
fn line_contains_var_in_call(line: &str, _sink_lower: &str, var: &str) -> bool {
    // For now, just check if the variable appears on the same line as the sink.
    // A more precise check would parse the argument list, but this is the heuristic approach.
    rhs_contains_var(line, var)
}

// ---- Tests -----------------------------------------------------------------

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

    fn sources() -> HashSet<String> {
        [
            "request.args",
            "request.form",
            "req.body",
            "req.query",
            "req.params",
            "params[",
        ]
        .iter()
        .map(|s| s.to_string())
        .collect()
    }

    fn sql_sinks() -> HashSet<String> {
        ["execute", "executemany", "raw_sql", "query(", "db.run"]
            .iter()
            .map(|s| s.to_string())
            .collect()
    }

    fn sanitizers() -> HashSet<String> {
        [
            "escape",
            "sanitize",
            "parameterize",
            "prepare",
            "bindparam",
            "html.escape",
        ]
        .iter()
        .map(|s| s.to_string())
        .collect()
    }

    #[test]
    fn test_python_basic_taint_flow() {
        let code = r#"
user_input = request.args.get("q")
query = "SELECT * FROM t WHERE x = '" + user_input + "'"
cursor.execute(query)
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::Python,
            TaintCategory::SqlInjection,
            &sources(),
            &sql_sinks(),
            &sanitizers(),
        );

        assert!(
            !result.sink_reaches.is_empty(),
            "Should detect taint reaching execute()"
        );
        assert_eq!(result.sink_reaches[0].sink_pattern, "execute");
        assert!(!result.sink_reaches[0].is_sanitized);
    }

    #[test]
    fn test_python_fstring_propagation() {
        let code = r#"
user_input = request.args.get("q")
query = f"SELECT * FROM t WHERE x = '{user_input}'"
cursor.execute(query)
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::Python,
            TaintCategory::SqlInjection,
            &sources(),
            &sql_sinks(),
            &sanitizers(),
        );

        assert!(
            !result.sink_reaches.is_empty(),
            "Should detect f-string taint propagation"
        );
    }

    #[test]
    fn test_python_sanitized_flow() {
        let code = r#"
user_input = request.args.get("q")
clean_input = escape(user_input)
query = f"SELECT * FROM t WHERE x = '{clean_input}'"
cursor.execute(query)
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::Python,
            TaintCategory::SqlInjection,
            &sources(),
            &sql_sinks(),
            &sanitizers(),
        );

        // clean_input should be sanitized, so no vulnerable sink reaches
        let vulnerable: Vec<_> = result
            .sink_reaches
            .iter()
            .filter(|r| !r.is_sanitized)
            .collect();
        assert!(
            vulnerable.is_empty(),
            "Sanitized flow should not be flagged"
        );
        assert!(result.sanitized_vars.contains("clean_input"));
    }

    #[test]
    fn test_javascript_taint_flow() {
        let code = r#"
const userInput = req.body.username;
const query = "SELECT * FROM users WHERE name = '" + userInput + "'";
db.run(query);
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::JavaScript,
            TaintCategory::SqlInjection,
            &sources(),
            &sql_sinks(),
            &sanitizers(),
        );

        assert!(
            !result.sink_reaches.is_empty(),
            "Should detect JS taint flow"
        );
    }

    #[test]
    fn test_go_taint_flow() {
        let code = r#"
userInput := req.query.Get("name")
query := "SELECT * FROM users WHERE name = '" + userInput + "'"
db.run(query)
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::Go,
            TaintCategory::SqlInjection,
            &sources(),
            &sql_sinks(),
            &sanitizers(),
        );

        assert!(
            !result.sink_reaches.is_empty(),
            "Should detect Go taint flow"
        );
    }

    #[test]
    fn test_rust_taint_flow() {
        let code = r#"
let user_input = req.query("name");
let query = format!("SELECT * FROM users WHERE name = '{}'", user_input);
db.run(&query);
"#;
        let flow = HeuristicFlow::new();

        // Add format! as propagation-aware
        let mut srcs = sources();
        srcs.insert("req.query".to_string());

        let result = flow.analyze_intra_function(
            code,
            Language::Rust,
            TaintCategory::SqlInjection,
            &srcs,
            &sql_sinks(),
            &sanitizers(),
        );

        assert!(
            result.tainted_vars.contains_key("user_input"),
            "user_input should be tainted"
        );
    }

    #[test]
    fn test_no_taint_no_findings() {
        let code = r#"
x = 42
y = x + 1
print(y)
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::Python,
            TaintCategory::SqlInjection,
            &sources(),
            &sql_sinks(),
            &sanitizers(),
        );

        assert!(
            result.sink_reaches.is_empty(),
            "No taint sources means no findings"
        );
        assert!(result.tainted_vars.is_empty());
    }

    #[test]
    fn test_taint_propagation_chain() {
        let code = r#"
raw = request.args.get("input")
step1 = raw
step2 = step1
step3 = step2
cursor.execute(step3)
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::Python,
            TaintCategory::SqlInjection,
            &sources(),
            &sql_sinks(),
            &sanitizers(),
        );

        assert!(
            result.tainted_vars.contains_key("step3"),
            "Taint should propagate through chain"
        );
        assert!(
            !result.sink_reaches.is_empty(),
            "Should detect taint at end of chain"
        );
    }

    #[test]
    fn test_command_injection_flow() {
        let cmd_sinks: HashSet<String> = [
            "system",
            "exec",
            "popen",
            "subprocess.run",
            "subprocess.call",
        ]
        .iter()
        .map(|s| s.to_string())
        .collect();

        let code = r#"
filename = request.form.get("file")
cmd = "cat " + filename
os.system(cmd)
"#;
        let flow = HeuristicFlow::new();
        let result = flow.analyze_intra_function(
            code,
            Language::Python,
            TaintCategory::CommandInjection,
            &sources(),
            &cmd_sinks,
            &sanitizers(),
        );

        assert!(
            !result.sink_reaches.is_empty(),
            "Should detect command injection flow"
        );
    }

    #[test]
    fn test_is_simple_var() {
        assert!(is_simple_var("x"));
        assert!(is_simple_var("user_input"));
        assert!(is_simple_var("_private"));
        assert!(is_simple_var("camelCase"));
        assert!(!is_simple_var("obj.field"));
        assert!(!is_simple_var("arr[0]"));
        assert!(!is_simple_var(""));
        assert!(!is_simple_var("123abc"));
    }

    #[test]
    fn test_rhs_contains_var_word_boundary() {
        assert!(rhs_contains_var("foo + bar", "foo"));
        assert!(rhs_contains_var("func(foo)", "foo"));
        assert!(rhs_contains_var("f\"{foo}\"", "foo"));
        assert!(!rhs_contains_var("foobar", "foo"));
        assert!(!rhs_contains_var("barfoo", "foo"));
        assert!(!rhs_contains_var("_foo", "foo"));
        assert!(rhs_contains_var("a + foo + b", "foo"));
    }
}