provide-telemetry 0.7.2

// SPDX-FileCopyrightText: Copyright (C) 2026 provide.io llc
// SPDX-License-Identifier: Apache-2.0
// SPDX-Comment: Part of provide-telemetry.
//

use regex::Regex;
use serde_json::{Map, Value};
use sha2::{Digest, Sha256};
use std::sync::{Mutex, OnceLock};

use crate::classification::{classify_key, get_classification_policy};
use crate::receipts::record_redaction;

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum PIIMode {
    Drop,
    Redact,
    Hash,
    Truncate,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct PIIRule {
    pub path: Vec<String>,
    pub mode: PIIMode,
    pub truncate_to: usize,
}

impl PIIRule {
    pub fn new(path: Vec<String>, mode: PIIMode, truncate_to: usize) -> Self {
        Self {
            path,
            mode,
            truncate_to,
        }
    }
}

const REDACTED: &str = "***";
const TRUNC_SUFFIX: &str = "...";
const DEFAULT_SENSITIVE: &[&str] = &[
    "password",
    "passwd",
    "secret",
    "token",
    "api_key",
    "apikey",
    "auth",
    "authorization",
    "credential",
    "private_key",
    "ssn",
    "credit_card",
    "creditcard",
    "cvv",
    "pin",
    "account_number",
    "cookie",
];

/// A secret pattern with a diagnostic name and the compiled regex.
#[derive(Clone, Debug)]
pub struct SecretPattern {
    pub name: String,
    pub pattern: Regex,
}

static RULES: OnceLock<Mutex<Vec<PIIRule>>> = OnceLock::new();
static CUSTOM_SECRET_PATTERNS: OnceLock<Mutex<Vec<(String, Regex)>>> = OnceLock::new();

#[cfg_attr(test, mutants::skip)] // Equivalent mutants only rewrite Vec::new() syntax.
fn empty_pii_rules_mutex() -> Mutex<Vec<PIIRule>> {
    Mutex::new(Vec::new())
}

fn rules() -> &'static Mutex<Vec<PIIRule>> {
    RULES.get_or_init(empty_pii_rules_mutex)
}

#[cfg_attr(test, mutants::skip)] // Equivalent mutants only rewrite Vec::new() syntax.
fn empty_custom_patterns_mutex() -> Mutex<Vec<(String, Regex)>> {
    Mutex::new(Vec::new())
}

fn custom_secret_patterns() -> &'static Mutex<Vec<(String, Regex)>> {
    CUSTOM_SECRET_PATTERNS.get_or_init(empty_custom_patterns_mutex)
}

fn compiled_builtin_secret_patterns() -> Vec<Regex> {
    crate::secret_patterns_generated::PATTERNS
        .iter()
        .map(|(_name, pattern)| Regex::new(pattern).expect("generated pattern must be valid"))
        .collect()
}

fn builtin_secret_patterns() -> &'static [Regex] {
    static COMPILED: OnceLock<Vec<Regex>> = OnceLock::new();
    COMPILED
        .get_or_init(compiled_builtin_secret_patterns)
        .as_slice()
}

/// How many slash-separated parts a span needs before its shape reads as a path.
const PATH_MIN_SEGMENTS: usize = 3;

/// True when a matched span is a filesystem path rather than a secret.
///
/// The long_base64 pattern is `[A-Za-z0-9+/]{40,}` and `/` belongs to the
/// base64 alphabet, so any deep path of unpunctuated segments matched it:
/// `/home/deploy/apps/production/current/lib/service` is 48 characters of pure
/// base64 alphabet containing no secret. Narrowing the charset is not the fix —
/// dropping `/` costs 44% of detections on 32-byte secrets, because a 44-char
/// base64 string holding one slash cannot be told from a path by charset alone.
///
/// Shape separates them: a path carries several short all-lowercase words
/// (usr, local, lib), which random base64 effectively never yields — a
/// 20-character all-lowercase run has probability (26/64)^20, about 1e-8.
fn looks_like_path(span: &str) -> bool {
    let segments: Vec<&str> = span.split('/').filter(|s| !s.is_empty()).collect();
    if segments.len() < PATH_MIN_SEGMENTS {
        return false;
    }
    let wordy = segments
        .iter()
        .filter(|s| !s.is_empty() && s.chars().all(|c| c.is_ascii_lowercase()))
        .count();
    wordy * 2 >= segments.len()
}

/// Every secret-looking byte span in *text*, widened to whole tokens, sorted
/// and coalesced.
///
/// Every pattern is scanned across the WHOLE value, not stopped at its first
/// match, and every pattern is tried even after one has hit. Skipping either
/// leaks:
///
/// - Stopping a pattern at its first match let a path shadow a real secret.
///   long_base64 matches a path first; suppressing that match as path-shaped
///   moved the scan to the next pattern, and long_base64 is the last one, so
///   the credential behind the path was never looked for at all.
/// - Stopping at the first pattern to hit left a field's second and third
///   secrets in the log, which whole-value blanking used to cover for free.
///
/// `find` runs first as a fast path: a clean value, which is nearly every log
/// field, allocates nothing, because `find_iter` is only entered once a
/// pattern is known to match.
fn secret_spans(text: &str) -> Vec<(usize, usize)> {
    if text.len() < crate::secret_patterns_generated::MIN_SECRET_LENGTH {
        return Vec::new();
    }
    let mut spans: Vec<(usize, usize)> = Vec::new();
    let mut collect = |pattern: &Regex| {
        if pattern.find(text).is_none() {
            return;
        }
        for m in pattern.find_iter(text) {
            // A registered pattern that can match the empty string carries no
            // secret; widening a zero-length match to its token would redact a
            // word for nothing.
            if m.start() == m.end() {
                continue;
            }
            if !looks_like_path(m.as_str()) {
                spans.push(expand_to_token(text, m.start(), m.end()));
            }
        }
    };
    for pattern in builtin_secret_patterns() {
        collect(pattern);
    }
    {
        let patterns = crate::_lock::lock(custom_secret_patterns());
        for (_, pattern) in patterns.iter() {
            collect(pattern);
        }
    }
    merge_spans(spans)
}

/// Widen a match to its whitespace-delimited token.
///
/// Redacting the literal match alone can leave part of a credential behind:
/// the jwt pattern matches header.payload, and a JWT has THREE dot-separated
/// parts, so the signature would survive. Whitespace is the boundary a secret
/// cannot cross without ceasing to be one token.
///
/// Found by search rather than by walking an index. A `while` loop stepping an
/// index is one mutated assignment away from never terminating -- `start -= 1`
/// becoming `start /= 1` hangs the process -- and a hung mutant is a gap in the
/// suite that reads as a timeout rather than as a failure.
fn expand_to_token(text: &str, start: usize, end: usize) -> (usize, usize) {
    let left = text[..start]
        .rfind(|c: char| c.is_ascii_whitespace())
        .map_or(0, |index| index + 1);
    let right = text[end..]
        .find(|c: char| c.is_ascii_whitespace())
        .map_or(text.len(), |index| end + index);
    (left, right)
}

/// Sort and coalesce overlapping spans so each region is replaced once. Two
/// patterns can match the same credential -- long_base64 and jwt both hit a
/// JWT -- and after widening they overlap exactly, which would emit "******".
///
/// There is deliberately no `spans.len() < 2` shortcut. It saved nothing the
/// loop below does not already handle for zero or one span, and every mutant
/// of its comparison either changed behaviour in a way no test could see or
/// skipped the merge for exactly two spans.
fn merge_spans(mut spans: Vec<(usize, usize)>) -> Vec<(usize, usize)> {
    spans.sort_unstable();
    let mut merged: Vec<(usize, usize)> = Vec::with_capacity(spans.len());
    for (start, end) in spans {
        match merged.last_mut() {
            Some(last) if start <= last.1 => last.1 = last.1.max(end),
            _ => merged.push((start, end)),
        }
    }
    merged
}

/// Redacted form of *text*, or None when it holds no secret.
///
/// Every secret-looking token is replaced and the rest stays readable. Every
/// span goes, not just the first: whole-value blanking removed a field's
/// second and third credentials for free, and scoping redaction to a token
/// silently dropped that guarantee.
///
/// Each match is widened to its whitespace-delimited token first. Redacting
/// the literal match alone can leave part of a credential behind: the jwt
/// pattern matches header.payload, and a JWT has THREE dot-separated parts, so
/// the signature would survive. Whitespace is the boundary a secret cannot
/// cross without ceasing to be one token.
///
/// Returning an Option rather than the string keeps callers to one scan;
/// asking whether a value held a secret and then redacting it ran the whole
/// pattern sweep twice for every value carrying a credential.
pub(crate) fn redact_if_secret(text: &str) -> Option<String> {
    let spans = secret_spans(text);
    if spans.is_empty() {
        return None;
    }
    let mut out = String::with_capacity(text.len());
    let mut previous_end = 0usize;
    for (start, end) in spans {
        out.push_str(&text[previous_end..start]);
        out.push_str(REDACTED);
        previous_end = end;
    }
    out.push_str(&text[previous_end..]);
    Some(out)
}

/// The redaction sentinel emitted when a value or string matches a
/// secret pattern (matches Python's `***` and Go's `piicore.Redacted`).
pub(crate) const REDACTED_SENTINEL: &str = REDACTED;

/// Register a custom secret detection pattern. If *name* already exists, the
/// pattern is replaced.
pub fn register_secret_pattern(name: &str, pattern: Regex) {
    let mut patterns = crate::_lock::lock(custom_secret_patterns());
    if let Some((_, existing)) = patterns
        .iter_mut()
        .find(|(existing_name, _)| existing_name == name)
    {
        *existing = pattern;
    } else {
        patterns.push((name.to_string(), pattern));
    }
}

/// Return all secret patterns (built-in and custom).
pub fn get_secret_patterns() -> Vec<SecretPattern> {
    let mut out: Vec<SecretPattern> = crate::secret_patterns_generated::PATTERNS
        .iter()
        .zip(builtin_secret_patterns().iter())
        .map(|((name, _), p)| SecretPattern {
            name: name.to_string(),
            pattern: p.clone(),
        })
        .collect();
    let patterns = crate::_lock::lock(custom_secret_patterns());
    for (name, pattern) in patterns.iter() {
        out.push(SecretPattern {
            name: name.clone(),
            pattern: pattern.clone(),
        });
    }
    out
}

/// Reset custom secret patterns — for test isolation only.
pub fn reset_secret_patterns_for_tests() {
    crate::_lock::lock(custom_secret_patterns()).clear();
}

pub fn register_pii_rule(rule: PIIRule) {
    crate::_lock::lock(rules()).push(rule);
}

pub fn replace_pii_rules(next: Vec<PIIRule>) {
    *crate::_lock::lock(rules()) = next;
}

pub fn get_pii_rules() -> Vec<PIIRule> {
    crate::_lock::lock(rules()).clone()
}

fn hash_value(value: &Value) -> String {
    let mut hasher = Sha256::new();
    match value {
        Value::String(text) => hasher.update(text.as_bytes()),
        _ => hasher.update(value.to_string().as_bytes()),
    }
    let digest = hasher.finalize();
    format!("{:x}", digest)[..12].to_string()
}

fn mask_value(value: &Value, mode: &PIIMode, truncate_to: usize) -> Option<Value> {
    match mode {
        PIIMode::Drop => None,
        PIIMode::Redact => Some(Value::String(REDACTED.to_string())),
        PIIMode::Hash => Some(Value::String(hash_value(value))),
        PIIMode::Truncate => {
            let text = match value {
                Value::String(value) => value.clone(),
                _ => value.to_string(),
            };
            let char_count = text.chars().count();
            if char_count <= truncate_to {
                Some(Value::String(text))
            } else {
                let head: String = text.chars().take(truncate_to).collect();
                Some(Value::String(format!("{head}{TRUNC_SUFFIX}")))
            }
        }
    }
}

/// Segment-wise path match: `"*"` in *rule_path* matches any single segment.
fn match_rule_path(rule_path: &[String], child_path: &[String]) -> bool {
    if rule_path.len() != child_path.len() {
        return false;
    }
    rule_path
        .iter()
        .zip(child_path.iter())
        .all(|(rp, cp)| rp == "*" || rp == cp)
}

fn apply_rules(node: &Value, path: &[String], rules: &[PIIRule], max_depth: usize) -> Value {
    if max_depth == 0 {
        return node.clone();
    }

    match node {
        Value::Object(map) => {
            let mut out = Map::new();
            for (key, value) in map {
                let mut child_path = path.to_vec();
                child_path.push(key.clone());
                if let Some(rule) = rules
                    .iter()
                    .find(|rule| match_rule_path(&rule.path, &child_path))
                {
                    if let Some(masked) = mask_value(value, &rule.mode, rule.truncate_to) {
                        out.insert(key.clone(), masked);
                    }
                    record_redaction(
                        &child_path.join("."),
                        &format!("{:?}", rule.mode).to_ascii_lowercase(),
                        value,
                    );
                    continue;
                }

                let lowered = key.to_ascii_lowercase();
                let sensitive_key = DEFAULT_SENSITIVE
                    .iter()
                    .any(|candidate| candidate == &lowered);
                // Span-scoped for a secret-bearing string: only the credential
                // tokens go. A sensitive KEY still blanks wholesale, since
                // there the whole value is the secret.
                //
                // One scan, not two: asking whether the value held a secret
                // and then redacting it ran the whole pattern sweep twice for
                // every value carrying a credential. Only a string can hold
                // one, so no other variant is scanned.
                let replacement = if sensitive_key {
                    Some(REDACTED.to_string())
                } else {
                    match value {
                        Value::String(text) => redact_if_secret(text),
                        _ => None,
                    }
                };
                if let Some(replacement) = replacement {
                    out.insert(key.clone(), Value::String(replacement));
                    record_redaction(&child_path.join("."), "redact", value);
                    continue;
                }

                out.insert(
                    key.clone(),
                    apply_rules(value, &child_path, rules, max_depth - 1),
                );
            }
            Value::Object(out)
        }
        // Fix 5: push "*" as path segment when recursing into array elements so
        // rules like ["users", "*", "email"] can match each element's "email" key.
        Value::Array(values) => {
            let mut star_path = path.to_vec();
            star_path.push("*".to_string());
            Value::Array(
                values
                    .iter()
                    .map(|value| apply_rules(value, &star_path, rules, max_depth - 1))
                    .collect(),
            )
        }
        _ => node.clone(),
    }
}

fn annotate_governance_classes(cleaned: &mut Value) {
    let Value::Object(map) = cleaned else {
        return;
    };
    let policy = get_classification_policy();
    let keys: Vec<String> = map.keys().cloned().collect();
    for key in keys {
        if let Some(label) = classify_key(&key) {
            let action = policy.lookup_action(&label);
            if action == "drop" {
                map.remove(&key);
                continue;
            }
            if matches!(action, "redact" | "hash" | "truncate") {
                let current = map
                    .get(&key)
                    .cloned()
                    .expect("classification key snapshot must still exist");
                let already_redacted = current.as_str().map(|s| s == REDACTED).unwrap_or(false);
                if !already_redacted {
                    let mode = match action {
                        "redact" => PIIMode::Redact,
                        "hash" => PIIMode::Hash,
                        _ => PIIMode::Truncate,
                    };
                    let masked = mask_value(&current, &mode, 8)
                        .expect("classification governance modes never drop values");
                    map.insert(key.clone(), masked);
                }
            }
            map.insert(format!("__{key}__class"), Value::String(label));
        }
    }
}

pub fn sanitize_payload(payload: &Value, enabled: bool, max_depth: usize) -> Value {
    if !enabled {
        return payload.clone();
    }
    let rules = get_pii_rules();
    let mut cleaned = apply_rules(payload, &[], &rules, max_depth.max(1));
    annotate_governance_classes(&mut cleaned);
    cleaned
}

#[cfg(test)]
#[path = "pii_tests.rs"]
mod tests;