//! self-uninstall: remove agent-manager and everything it created from this
//! machine — background agents are stopped first, then the data, state and
//! configuration directories are deleted, then the executable itself.

use crate::app::{self, App};
use anyhow::{bail, Result};
#[cfg(unix)]
use anyhow::Context;
use colored::Colorize;
use std::path::{Path, PathBuf};

#[cfg(windows)]
const MOVEFILE_DELAY_UNTIL_REBOOT: u32 = 0x4;
#[cfg(windows)]
const FILE_ATTRIBUTE_READONLY: u32 = 0x1;
#[cfg(windows)]
const INVALID_FILE_ATTRIBUTES: u32 = 0xFFFF_FFFF;

#[cfg(windows)]
#[link(name = "Kernel32")]
extern "system" {
    fn MoveFileExW(
        lpExistingFileName: *const u16,
        lpNewFileName: *const u16,
        dwFlags: u32,
    ) -> i32;
    fn GetFileAttributesW(lpFileName: *const u16) -> u32;
    fn SetFileAttributesW(lpFileName: *const u16, dwFileAttributes: u32) -> i32;
}

pub fn run(app: &App) -> Result<i32> {
    // 1. Stop every managed background agent.
    let state = app.state.load()?;
    for (name, entry) in &state.installed {
        if let Some(pid) = entry.pid {
            if crate::process::is_running(pid) {
                app.log.info(&format!("stopping agent '{name}' (pid {pid})"));
                crate::process::stop_pid(pid, false, 1);
            }
        }
    }

    // 2. Collect the directories agent-manager owns.
    let data_root = app::data_dir();
    let state_root = app::state_dir();
    let mut roots: Vec<(&str, PathBuf)> = Vec::new();
    if data_root.is_dir() {
        roots.push(("data", data_root.clone()));
    }
    if state_root != data_root && state_root.is_dir() {
        roots.push(("state", state_root));
    }
    if let Some(dir) = crate::config::user_config_dir() {
        if dir.is_dir() {
            roots.push(("config", dir));
        }
    }

    let exe = std::env::current_exe().ok();
    let mut renamed: Option<PathBuf> = None;

    if roots.is_empty() {
        app.log
            .info("nothing to remove — agent-manager left no traces on this machine");
    } else {
        app.log.info("agent-manager will remove:");
        for (label, path) in &roots {
            println!("  {label}: {}", path.display());
        }
        if !app.confirm("Remove everything listed above?")? {
            app.log.info("cancelled — nothing was removed");
            return Ok(0);
        }
        if app.dry_run() {
            app.log.dry("nothing removed (dry run)");
            return Ok(0);
        }
        // Windows allows renaming a running executable (but not deleting
        // it): do it up-front so the original binary disappears immediately,
        // even if the deferred deletion has to wait for this process to exit.
        renamed = exe.as_deref().and_then(rename_for_deletion);
        if let Some(new) = &renamed {
            if let Some(old) = &exe {
                println!(
                    "{} {} -> {}",
                    "renamed:".cyan(),
                    old.display(),
                    new.display()
                );
            }
        }
        // Remove everything first; any message logged *after* deleting the
        // state directory would recreate the log folder, so the removal
        // itself is silent and the report below goes to plain stdout.
        // The removal is tolerant: read-only attributes are cleared and files
        // locked by other processes (for example the running am.exe when it
        // lives inside the data directory) are scheduled for deletion at the
        // next reboot instead of failing the whole uninstall.
        let mut locked: Vec<PathBuf> = Vec::new();
        for (_, path) in &roots {
            remove_tree(path, &mut locked);
        }
        for (_, path) in &roots {
            if !path.exists() {
                println!("{} {}", "removed:".green(), path.display());
            }
        }
        if !locked.is_empty() {
            let scheduled = schedule_locked(&locked);
            if !scheduled.is_empty() {
                println!(
                    "{} {} entrée(s) verrouillée(s) — suppression planifiée au prochain redémarrage",
                    "locked:".yellow(),
                    scheduled.len()
                );
            }
            if scheduled.len() != locked.len() {
                println!(
                    "{} {} entrée(s) verrouillée(s) — le processus différé les supprimera après la fermeture de am",
                    "deferred:".cyan(),
                    locked.len() - scheduled.len()
                );
            }
        }
    }

    // 3. Delete the executable itself, then sweep the directories left
    // empty behind it.
    let cleanup_roots: Vec<PathBuf> = roots.iter().map(|(_, p)| p.clone()).collect();
    match &exe {
        Some(e) => remove_self(e, renamed.as_deref(), &cleanup_roots)?,
        None => app.log
            .warn("cannot locate the agent-manager executable — delete it manually"),
    }
    Ok(0)
}

/// Recursively remove a tree, tolerating locked or read-only entries.
/// Paths that could not be removed are collected into `locked` so the
/// caller can schedule their deletion at the next reboot.
fn remove_tree(path: &Path, locked: &mut Vec<PathBuf>) {
    let meta = match std::fs::symlink_metadata(path) {
        Ok(m) => m,
        Err(_) => return,
    };
    if meta.is_dir() {
        if let Ok(entries) = std::fs::read_dir(path) {
            for entry in entries.flatten() {
                remove_tree(&entry.path(), locked);
            }
        }
        clear_readonly(path);
        if std::fs::remove_dir(path).is_err() {
            locked.push(path.to_path_buf());
        }
    } else {
        clear_readonly(path);
        if std::fs::remove_file(path).is_err() {
            locked.push(path.to_path_buf());
        }
    }
}

/// Clear the read-only attribute (a common cause of "Access denied" on
/// Windows, e.g. files extracted by Expand-Archive).
#[cfg(windows)]
fn clear_readonly(path: &Path) {
    use std::os::windows::ffi::OsStrExt;
    let wide: Vec<u16> = path
        .as_os_str()
        .encode_wide()
        .chain(std::iter::once(0))
        .collect();
    unsafe {
        let attrs = GetFileAttributesW(wide.as_ptr());
        if attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_READONLY) != 0 {
            SetFileAttributesW(wide.as_ptr(), attrs & !FILE_ATTRIBUTE_READONLY);
        }
    }
}

#[cfg(not(windows))]
fn clear_readonly(_path: &Path) {}

/// Schedule every locked path for deletion at the next reboot (Windows).
/// Returns the paths that could be scheduled.
#[cfg(windows)]
fn schedule_locked(locked: &[PathBuf]) -> Vec<PathBuf> {
    use std::os::windows::ffi::OsStrExt;
    let mut scheduled = Vec::new();
    for path in locked {
        let wide: Vec<u16> = path
            .as_os_str()
            .encode_wide()
            .chain(std::iter::once(0))
            .collect();
        let ok = unsafe {
            MoveFileExW(wide.as_ptr(), std::ptr::null(), MOVEFILE_DELAY_UNTIL_REBOOT) != 0
        };
        if ok {
            scheduled.push(path.clone());
        }
    }
    scheduled
}

#[cfg(not(windows))]
fn schedule_locked(_locked: &[PathBuf]) -> Vec<PathBuf> {
    Vec::new()
}

/// Delete the running executable. On Unix the file can be unlinked while it
/// runs; on Windows a hidden cmd re-tries the deletion right after this
/// process exits (the file is locked while we run). Empty directories left
/// behind under the removed roots are swept afterwards.
fn remove_self(exe: &Path, renamed: Option<&Path>, roots: &[PathBuf]) -> Result<()> {
    #[cfg(unix)]
    {
        std::fs::remove_file(exe)
            .with_context(|| format!("cannot remove {}", exe.display()))?;
        // Sweep empty directories upward, but never above a removed root.
        let mut dir = exe.parent();
        while let Some(d) = dir {
            if !roots.iter().any(|r| d.starts_with(r)) {
                break;
            }
            if std::fs::remove_dir(d).is_err() {
                break;
            }
            dir = d.parent();
        }
        println!(
            "{} {}",
            "agent-manager removed:".green(),
            exe.display()
        );
        return Ok(());
    }
    #[cfg(windows)]
    {
        use std::os::windows::ffi::OsStrExt;
        // The file to delete once this process exits: the renamed copy when
        // the up-front rename worked, the original path otherwise.
        let target = renamed.unwrap_or(exe);
        // A temporary batch file retries the deletion for a few seconds (the
        // image stays locked until we exit), sweeps the directories left
        // empty, then deletes itself. A .bat avoids every cmd /C command-line
        // quoting pitfall.
        let bat = write_cleanup_bat(exe, target, roots);
        if let Some(b) = &bat {
            // raw_arg passes the command line verbatim: regular .arg()
            // backslash-escapes embedded quotes, which cmd.exe does not
            // understand.
            use std::os::windows::process::CommandExt as _;
            let mut cleanup = std::process::Command::new("cmd");
            cleanup.raw_arg("/C");
            cleanup.raw_arg(format!("\"{}\"", b.display()));
            let _ = cleanup.spawn();
        }
        // Belt and braces: if something keeps the file locked, the standard
        // uninstaller mechanism deletes it at the next reboot.
        let wide: Vec<u16> = target
            .as_os_str()
            .encode_wide()
            .chain(std::iter::once(0))
            .collect();
        let at_reboot = unsafe {
            MoveFileExW(wide.as_ptr(), std::ptr::null(), MOVEFILE_DELAY_UNTIL_REBOOT) != 0
        };
        if bat.is_none() && !at_reboot {
            bail!(
                "cannot schedule deletion of {} — delete it manually",
                exe.display()
            );
        }
        if renamed.is_some() {
            println!(
                "{} {}",
                "agent-manager removed; the executable was renamed and will be deleted momentarily:".green(),
                exe.display()
            );
        } else {
            println!(
                "{} {}",
                "agent-manager removed; the executable will be deleted momentarily:".green(),
                exe.display()
            );
        }
        return Ok(());
    }
    #[cfg(not(any(unix, windows)))]
    {
        bail!(
            "automatic removal of the executable is not supported on this platform; delete {} manually",
            exe.display()
        );
    }
}

/// Rename the running executable out of the way (Windows allows renaming a
/// running image — only deletion is refused while it executes). Returns the
/// new path on success.
#[cfg(windows)]
fn rename_for_deletion(exe: &Path) -> Option<PathBuf> {
    let name = exe.file_name()?.to_string_lossy();
    let new = exe.with_file_name(format!("{name}.deleteme"));
    std::fs::rename(exe, &new).ok()?;
    Some(new)
}

#[cfg(not(windows))]
fn rename_for_deletion(_exe: &Path) -> Option<PathBuf> {
    None
}

/// Write a temporary batch file that deletes the target executable once it
/// is unlocked, sweeps the directories left empty and then removes itself.
#[cfg(windows)]
fn write_cleanup_bat(exe: &Path, target: &Path, roots: &[PathBuf]) -> Option<PathBuf> {
    let crlf = "\r\n";
    let q = "\"";
    let mut script = String::new();
    let mut line = |s: &str| {
        script.push_str(s);
        script.push_str(crlf);
    };
    line("@echo off");
    line("set n=0");
    line(":retry");
    line(&format!("del /f /q {q}{}{q} >nul 2>&1", target.display()));
    line(&format!("del /f /q {q}{}{q} >nul 2>&1", exe.display()));
    line(&format!(
        "if not exist {q}{}{q} (if not exist {q}{}{q} goto sweep)",
        target.display(),
        exe.display()
    ));
    line("set /a n+=1");
    line("if %n% GEQ 60 goto end");
    line("ping -n 2 127.0.0.1 >nul");
    line("goto retry");
    line(":sweep");
    if let Some(parent) = exe.parent() {
        if roots.iter().any(|r| parent.starts_with(r)) {
            line(&format!("rd /q {q}{}{q} >nul 2>&1", parent.display()));
        }
    }
    for root in roots {
        line(&format!("rd /q {q}{}{q} >nul 2>&1", root.display()));
    }
    line(":end");
    line(&format!("del {q}%~f0{q} >nul 2>&1"));
    let path = std::env::temp_dir().join(format!("am-uninstall-{}.bat", std::process::id()));
    std::fs::write(&path, script).ok()?;
    Some(path)
}

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

    #[test]
    fn removes_readonly_tree() {
        let dir = tempfile::tempdir().unwrap();
        let sub = dir.path().join("sub");
        std::fs::create_dir_all(&sub).unwrap();
        let file = sub.join("readonly.txt");
        std::fs::write(&file, "x").unwrap();
        // Read-only files are a classic cause of "Access denied" on Windows.
        let mut perms = std::fs::metadata(&file).unwrap().permissions();
        #[allow(clippy::permissions_set_readonly_false)]
        perms.set_readonly(true);
        std::fs::set_permissions(&file, perms).unwrap();

        let mut locked: Vec<PathBuf> = Vec::new();
        remove_tree(dir.path(), &mut locked);
        assert!(!dir.path().exists(), "tree should be fully removed");
        assert!(locked.is_empty(), "unexpected locked paths: {locked:?}");
    }

    #[test]
    fn tolerates_missing_tree() {
        let mut locked: Vec<PathBuf> = Vec::new();
        remove_tree(Path::new("/nonexistent/agent-manager-xyz"), &mut locked);
        assert!(locked.is_empty());
    }
}