//! Surface retrieval for absence-based controls.
//!
//! Some CRA controls are violated by an *absence* — no rate limiting on login, no
//! security logging, no signature check on an update — so there's no offending
//! pattern for semgrep to match. Instead we deterministically locate the code
//! *surface* the control governs (a login route, a logging setup, update/download
//! code) by identifier/route terms, then hand each surface region to the grounded
//! judge, which decides whether the control is satisfied there. The resulting
//! finding grounds to the surface snippet, so nothing fabricated survives.
//!
//! Retrieval is intentionally cheap and bounded: keyword match + a fixed window,
//! capped per control to keep the downstream LLM cost predictable.

use std::path::Path;

use compliance_core::control_check::CandidateRegion;

/// An absence-based control and the case-insensitive terms that mark the code
/// surface it governs.
pub struct Surface {
    pub control_id: &'static str,
    pub terms: &'static [&'static str],
}

/// The absence-based CRA controls we retrieve surfaces for — the grounded half of
/// the hybrid coverage (the pattern-expressible half is custom semgrep rules).
pub const SURFACES: &[Surface] = &[
    Surface {
        control_id: "cra-ai-6", // Integritaetspruefung
        terms: &[
            "checksum",
            "sha256",
            "signature",
            "hmac",
            "integrity",
            "verify",
        ],
    },
    Surface {
        control_id: "cra-ai-11", // Brute-Force-Schutz
        terms: &[
            "login",
            "signin",
            "authenticate",
            "/auth",
            "password",
            "ratelimit",
        ],
    },
    Surface {
        control_id: "cra-ai-12", // Rollenbasierte Autorisierung (RBAC)
        terms: &[
            "authorize",
            "permission",
            "role",
            "rbac",
            "require_role",
            "has_role",
        ],
    },
    Surface {
        control_id: "cra-ai-24", // Security-Logging
        terms: &["login", "authorize", "permission", "role", "admin", "audit"],
    },
    Surface {
        control_id: "cra-ai-27", // Log-Integritaet und -Aufbewahrung
        terms: &["logging", "logger", "getlogger", "audit_log"],
    },
    Surface {
        control_id: "cra-ai-28", // Sichere Update-Mechanismen
        terms: &["update", "upgrade", "download", "firmware"],
    },
    Surface {
        control_id: "cra-ai-29", // Update-Authentizitaet
        terms: &["update", "signature", "verify", "pubkey", "certificate"],
    },
    Surface {
        control_id: "cra-ai-30", // Update-Integritaet
        terms: &["update", "checksum", "digest", "integrity", "verify"],
    },
];

/// Source file extensions worth reading (skip binaries/assets/lockfiles).
const CODE_EXTS: &[&str] = &[
    "py", "js", "ts", "tsx", "jsx", "go", "java", "rb", "php", "rs", "cs", "kt",
];
/// Directories never worth walking.
const SKIP_DIRS: &[&str] = &[
    ".git",
    "node_modules",
    "target",
    "vendor",
    ".venv",
    "__pycache__",
    "dist",
    "build",
];
/// Lines of context on each side of a hit.
const WINDOW: usize = 6;
/// Cap on regions per control, to bound downstream LLM calls.
const MAX_REGIONS_PER_CONTROL: usize = 8;
/// Skip files larger than this (generated/minified).
const MAX_FILE_BYTES: u64 = 512 * 1024;

/// Deterministically retrieve up to [`MAX_REGIONS_PER_CONTROL`] code regions in
/// `repo_path` whose lines mention any of `terms`. Hits close together within a
/// file are merged into one region; results are capped to bound LLM cost.
pub fn retrieve(repo_path: &Path, terms: &[&str]) -> Vec<CandidateRegion> {
    let lowered: Vec<String> = terms.iter().map(|t| t.to_lowercase()).collect();
    let mut regions = Vec::new();
    for entry in walk(repo_path) {
        if regions.len() >= MAX_REGIONS_PER_CONTROL {
            break;
        }
        let path = entry.path();
        if !has_code_ext(path) {
            continue;
        }
        let Ok(meta) = entry.metadata() else { continue };
        if !meta.is_file() || meta.len() > MAX_FILE_BYTES {
            continue;
        }
        let Ok(content) = std::fs::read_to_string(path) else {
            continue;
        };
        let rel = path
            .strip_prefix(repo_path)
            .unwrap_or(path)
            .to_string_lossy()
            .to_string();
        let lines: Vec<&str> = content.lines().collect();
        let hits: Vec<usize> = lines
            .iter()
            .enumerate()
            .filter(|(_, line)| {
                let ll = line.to_lowercase();
                lowered.iter().any(|t| ll.contains(t.as_str()))
            })
            .map(|(i, _)| i)
            .collect();
        for center in merge_centers(&hits) {
            if regions.len() >= MAX_REGIONS_PER_CONTROL {
                break;
            }
            let start = center.saturating_sub(WINDOW);
            let end = (center + WINDOW + 1).min(lines.len());
            regions.push(CandidateRegion {
                file: rel.clone(),
                start_line: (start as u32) + 1,
                content: lines[start..end].join("\n"),
            });
        }
    }
    regions
}

/// Collapse ascending hit indices that fall within one window into a single
/// representative center, so overlapping regions aren't judged repeatedly.
fn merge_centers(hits: &[usize]) -> Vec<usize> {
    let mut out: Vec<usize> = Vec::new();
    for &h in hits {
        match out.last() {
            Some(&last) if h.saturating_sub(last) <= WINDOW => {}
            _ => out.push(h),
        }
    }
    out
}

fn has_code_ext(path: &Path) -> bool {
    path.extension()
        .and_then(|e| e.to_str())
        .is_some_and(|e| CODE_EXTS.contains(&e))
}

fn walk(root: &Path) -> Vec<walkdir::DirEntry> {
    walkdir::WalkDir::new(root)
        .into_iter()
        .filter_entry(|e| {
            let name = e.file_name().to_string_lossy();
            !SKIP_DIRS.contains(&name.as_ref())
        })
        .filter_map(|e| e.ok())
        .collect()
}

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

    fn write(dir: &Path, rel: &str, body: &str) {
        let p = dir.join(rel);
        if let Some(parent) = p.parent() {
            std::fs::create_dir_all(parent).unwrap();
        }
        std::fs::write(p, body).unwrap();
    }

    fn terms_for(control_id: &str) -> &'static [&'static str] {
        SURFACES
            .iter()
            .find(|s| s.control_id == control_id)
            .unwrap()
            .terms
    }

    #[test]
    fn surfaces_cover_the_absence_based_controls() {
        assert_eq!(SURFACES.len(), 8);
        for id in [
            "cra-ai-6",
            "cra-ai-11",
            "cra-ai-12",
            "cra-ai-24",
            "cra-ai-27",
            "cra-ai-28",
            "cra-ai-29",
            "cra-ai-30",
        ] {
            assert!(SURFACES.iter().any(|s| s.control_id == id), "{id} missing");
        }
    }

    #[test]
    fn retrieves_matching_region_with_context() {
        let dir = std::env::temp_dir().join(format!("surface-{}", uuid::Uuid::new_v4()));
        std::fs::create_dir_all(&dir).unwrap();
        write(
            &dir,
            "app/auth.py",
            "import x\n\n\n\n\n\n\ndef login(u, p):\n    return check(u, p)\n",
        );
        let regions = retrieve(&dir, terms_for("cra-ai-11"));
        assert_eq!(regions.len(), 1);
        assert!(regions[0].content.contains("def login"));
        assert_eq!(regions[0].file, "app/auth.py");
        let _ = std::fs::remove_dir_all(&dir);
    }

    #[test]
    fn skips_non_code_and_vendored() {
        let dir = std::env::temp_dir().join(format!("surface-{}", uuid::Uuid::new_v4()));
        std::fs::create_dir_all(&dir).unwrap();
        write(&dir, "README.md", "login and password and audit\n"); // not code ext
        write(&dir, "node_modules/pkg/index.js", "function login() {}\n"); // vendored
        assert!(retrieve(&dir, terms_for("cra-ai-11")).is_empty());
        let _ = std::fs::remove_dir_all(&dir);
    }

    #[test]
    fn merges_adjacent_hits_into_one_region() {
        // Two hits one line apart collapse to a single center/region.
        assert_eq!(merge_centers(&[10, 11, 30]), vec![10, 30]);
        assert_eq!(merge_centers(&[]), Vec::<usize>::new());
        assert_eq!(merge_centers(&[5]), vec![5]);
    }
}
