//! Local diagnostics in `<app data>/logs`: `host.log` (this process: start, saved state, sidecar, panics) and
//! `webview.log` (uncaught errors of the window, sent through the `log_webview` command). Each file is rotated at
//! MAX_BYTES (one older `.1.log` kept). Every line goes through `sanitize`: the home folder shows as `~`, and keys,
//! tokens, long secrets and e-mail addresses are replaced, so a log can be attached to a bug report as it is.
use std::fs::{self, OpenOptions};
use std::io::Write;
use std::path::{Path, PathBuf};
use std::sync::{Mutex, OnceLock};

pub const DIR: &str = "logs";
pub const HOST: &str = "host.log";
pub const WEBVIEW: &str = "webview.log";
pub const MAX_BYTES: u64 = 512 * 1024;
/// Longest single entry kept (the rest is cut).
pub const MAX_ENTRY: usize = 16 * 1024;

struct Logs {
    dir: PathBuf,
    home: Option<String>,
    lock: Mutex<()>,
}

static LOGS: OnceLock<Logs> = OnceLock::new();

/// Sets the log folder once (the first call wins).
pub fn init(data_dir: &Path, home: Option<String>) {
    let _ = LOGS.set(Logs { dir: data_dir.join(DIR), home, lock: Mutex::new(()) });
}

pub fn dir() -> Option<PathBuf> {
    LOGS.get().map(|l| l.dir.clone())
}

/// One line in host.log (no-op before `init`).
pub fn host(level: &str, message: &str) {
    write(HOST, "host", level, message);
}

/// One entry in webview.log.
pub fn webview(level: &str, message: &str) {
    write(WEBVIEW, "webview", level, message);
}

fn write(file: &str, source: &str, level: &str, message: &str) {
    let Some(l) = LOGS.get() else { return };
    let _g = l.lock.lock();
    let level = match level {
        "error" | "warn" | "info" | "debug" => level,
        _ => "info",
    };
    let text = sanitize(message, l.home.as_deref());
    let line = entry(&crate::store::now_iso(), source, level, &text);
    let _ = append(&l.dir, file, &line);
}

/// `<time> <level> [<source>] <text>`; continuation lines are indented.
pub fn entry(at: &str, source: &str, level: &str, text: &str) -> String {
    let mut t: String = text.chars().take(MAX_ENTRY).collect();
    if t.len() < text.len() {
        t.push_str(" [cut]");
    }
    format!("{at} {level:<5} [{source}] {}\n", t.trim_end().replace('\n', "\n    "))
}

/// Appends, rotating first when the file would pass MAX_BYTES.
pub fn append(dir: &Path, file: &str, line: &str) -> std::io::Result<()> {
    fs::create_dir_all(dir)?;
    let path = dir.join(file);
    if fs::metadata(&path).map(|m| m.len() + line.len() as u64 > MAX_BYTES).unwrap_or(false) {
        let old = dir.join(file.replace(".log", ".1.log"));
        let _ = fs::remove_file(&old);
        fs::rename(&path, &old)?;
    }
    OpenOptions::new().create(true).append(true).open(&path)?.write_all(line.as_bytes())
}

const SECRET_KEYS: &[&str] = &["secret", "token", "password", "passwd", "private_key", "privatekey", "apikey", "api_key", "authorization", "credential", "p8"];

/// The home folder as `~`, then keys, tokens and e-mail addresses replaced. Control characters other than newline and
/// tab are dropped.
pub fn sanitize(text: &str, home: Option<&str>) -> String {
    let mut s: String = text.chars().filter(|c| !c.is_control() || *c == '\n' || *c == '\t').collect();
    if let Some(h) = home.map(|h| h.trim_end_matches(['/', '\\'])).filter(|h| h.len() > 1) {
        s = s.replace(h, "~");
    }
    s = redact_pem(&s);
    s = redact_assignments(&s);
    redact_words(&s)
}

fn redact_pem(s: &str) -> String {
    let mut out = String::new();
    let mut rest = s;
    while let Some(i) = rest.find("-----BEGIN") {
        out.push_str(&rest[..i]);
        let after = &rest[i..];
        match after.find("-----END").and_then(|e| after[e + 8..].find("-----").map(|k| e + 8 + k + 5)) {
            Some(end) => {
                out.push_str("[redacted key]");
                rest = &after[end..];
            }
            None => {
                out.push_str("[redacted key]");
                rest = "";
            }
        }
    }
    out.push_str(rest);
    out
}

/// `token=...`, `"password": "..."`, `Authorization: Bearer ...`: the value goes.
fn redact_assignments(s: &str) -> String {
    let lower = s.to_ascii_lowercase();
    let b = s.as_bytes();
    let mut cut: Vec<(usize, usize)> = Vec::new();
    for k in SECRET_KEYS {
        let mut from = 0;
        while let Some(i) = lower[from..].find(k) {
            let mut j = i + from + k.len();
            from = j;
            // rest of the key name ("tokenId", "secret_key"), a closing quote, spaces, then ':' or '='
            while j < b.len() && (b[j].is_ascii_alphanumeric() || b[j] == b'_' || b[j] == b'-') {
                j += 1;
            }
            while j < b.len() && (b[j] == b'"' || b[j] == b'\'' || b[j] == b' ') {
                j += 1;
            }
            if j >= b.len() || (b[j] != b':' && b[j] != b'=') {
                continue;
            }
            j += 1;
            while j < b.len() && (b[j] == b' ' || b[j] == b'"' || b[j] == b'\'') {
                j += 1;
            }
            if lower[j..].starts_with("bearer ") || lower[j..].starts_with("basic ") {
                j += lower[j..].find(' ').unwrap_or(0) + 1;
            }
            let start = j;
            while j < b.len() && !matches!(b[j], b'"' | b'\'' | b',' | b'}' | b' ' | b'\n' | b'&' | b';') {
                j += 1;
            }
            if j > start {
                cut.push((start, j));
            }
        }
    }
    cut.sort();
    let mut out = String::new();
    let mut at = 0;
    for (a, z) in cut {
        if a < at {
            continue;
        }
        out.push_str(&s[at..a]);
        out.push_str("[redacted]");
        at = z;
    }
    out.push_str(&s[at..]);
    out
}

/// Long random-looking words (keys, JWTs, hashes of 32+ characters with letters and digits) and e-mail addresses.
fn redact_words(s: &str) -> String {
    let is_word = |c: char| c.is_ascii_alphanumeric() || matches!(c, '_' | '-' | '+' | '/' | '=' | '.' | '@');
    let mut out = String::with_capacity(s.len());
    let mut word = String::new();
    let flush = |w: &mut String, out: &mut String| {
        if !w.is_empty() {
            out.push_str(&judge(w));
            w.clear();
        }
    };
    for c in s.chars() {
        if is_word(c) {
            word.push(c);
        } else {
            flush(&mut word, &mut out);
            out.push(c);
        }
    }
    flush(&mut word, &mut out);
    out
}

fn judge(w: &str) -> String {
    if let Some((user, domain)) = w.split_once('@') {
        if !user.is_empty() && domain.contains('.') && !domain.starts_with('.') {
            return "[email]".into();
        }
    }
    let mixed = |p: &str| p.chars().any(|c| c.is_ascii_alphabetic()) && p.chars().any(|c| c.is_ascii_digit());
    // a long base64 / hex run (may hold '/' or '+'): not a path, not a dotted name
    if w.len() >= 40 && !w.starts_with(['/', '~']) && !w.contains('.') && mixed(w) {
        return "[redacted]".into();
    }
    // paths and dotted names stay (file names in stacks); one long run of key-like characters inside them goes
    for part in w.split(['/', '.']) {
        if part.len() >= 32 && mixed(part) {
            return w.replace(part, "[redacted]");
        }
    }
    w.to_string()
}

/// Records panics in host.log (release builds abort right after).
pub fn panic_hook() {
    let prev = std::panic::take_hook();
    std::panic::set_hook(Box::new(move |info| {
        host("error", &format!("panic: {info}"));
        prev(info);
    }));
}