use std::ffi::OsStr;
use std::path::Path;
use std::path::PathBuf;

use color_eyre::eyre::Context;
use color_eyre::eyre::Result;
use serde::Deserialize;
use strum::Display;

use crate::command::CommandExt;
use crate::error::UnsupportedSudo;
use crate::execution_context::ExecutionContext;
use crate::executor::Executor;
use crate::terminal::print_separator;
use crate::utils::which;

#[derive(Clone, Debug)]
pub struct Sudo {
    /// The path to the `sudo` binary.
    path: Option<PathBuf>,
    /// The type of program being used as `sudo`.
    kind: SudoKind,
}

#[derive(Clone, Debug, Default)]
pub enum SudoPreserveEnv<'a> {
    /// Preserve all environment variables.
    All,
    /// Preserve only the specified environment variables.
    Some(&'a [&'a str]),
    /// Preserve no environment variables.
    #[default]
    None,
}

/// Generic sudo options, translated into flags to pass to `sudo`.
/// NOTE: Depending on the sudo kind, OS and system config, some options might be specified by
/// default or unsupported.
#[derive(Clone, Debug, Default)]
pub struct SudoExecuteOpts<'a> {
    /// Run the command inside a login shell.
    pub login_shell: bool,
    /// Preserve environment variables across the sudo call.
    pub preserve_env: SudoPreserveEnv<'a>,
    /// Set the HOME environment variable to the target user's home directory.
    pub set_home: bool,
    /// Run the command as a user other than the root user.
    pub user: Option<&'a str>,
}

impl<'a> SudoExecuteOpts<'a> {
    pub fn new() -> Self {
        Self::default()
    }

    /// Run the command inside a login shell.
    #[allow(unused)]
    pub fn login_shell(mut self) -> Self {
        self.login_shell = true;
        self
    }

    /// Preserve all environment variables across the sudo call.
    #[allow(unused)]
    pub fn preserve_env(mut self) -> Self {
        self.preserve_env = SudoPreserveEnv::All;
        self
    }

    /// Preserve only the specified environment variables across the sudo call.
    #[allow(unused)]
    pub fn preserve_env_list(mut self, vars: &'a [&'a str]) -> Self {
        self.preserve_env = SudoPreserveEnv::Some(vars);
        self
    }

    /// Set the HOME environment variable to the target user's home directory.
    #[allow(unused)]
    pub fn set_home(mut self) -> Self {
        self.set_home = true;
        self
    }

    /// Run the command as a user other than the root user.
    #[allow(unused)]
    pub fn user(mut self, user: &'a str) -> Self {
        self.user = Some(user);
        self
    }
}

#[cfg(not(target_os = "windows"))]
const DETECT_ORDER: [SudoKind; 5] = [
    SudoKind::Doas,
    SudoKind::Sudo,
    SudoKind::Pkexec,
    SudoKind::Run0,
    SudoKind::Please,
];

#[cfg(target_os = "windows")]
const DETECT_ORDER: [SudoKind; 2] = [SudoKind::Gsudo, SudoKind::WinSudo];

impl Sudo {
    /// Get the `sudo` binary for this platform.
    pub fn detect() -> Option<Self> {
        for kind in DETECT_ORDER {
            if let Some(sudo) = Self::new(kind) {
                return Some(sudo);
            }
        }
        None
    }

    /// Create Sudo from SudoKind, if found in the system
    pub fn new(kind: SudoKind) -> Option<Self> {
        match kind {
            SudoKind::Null => Some(Self {
                path: None, // no actual binary for null sudo
                kind,
            }),
            _ => kind.which().map(|path| Self { path: Some(path), kind }),
        }
    }

    /// Gets the path to the `sudo` binary. Do not use this to execute `sudo` directly - either use
    /// [`Sudo::elevate`], or if you need to specify arguments to `sudo`, use [`Sudo::elevate_opts`].
    /// This way, sudo options can be specified generically and the actual arguments customized
    /// depending on the sudo kind.
    #[allow(unused)]
    pub fn path(&self) -> Option<&Path> {
        self.path.as_deref()
    }

    /// Elevate permissions with `sudo`.
    ///
    /// This helps prevent blocking `sudo` prompts from stopping the run in the middle of a
    /// step.
    ///
    /// See: https://github.com/topgrade-rs/topgrade/issues/205
    pub fn elevate(&self, ctx: &ExecutionContext) -> Result<()> {
        // skip if using null sudo
        if let SudoKind::Null = self.kind {
            return Ok(());
        }

        print_separator("Sudo");

        // self.path is only None for null sudo, which we've handled above
        let mut cmd = ctx.execute(self.path.as_deref().unwrap());
        match self.kind {
            SudoKind::Doas => {
                // `doas` doesn't have anything like `sudo -v` to cache credentials,
                // so we just execute a dummy `echo` command so we have something
                // unobtrusive to run.
                // See: https://man.openbsd.org/doas
                cmd.arg("echo");
            }
            SudoKind::Sudo => {
                // From `man sudo` on macOS:
                //   -v, --validate
                //   Update the user's cached credentials, authenticating the user
                //   if necessary.  For the sudoers plugin, this extends the sudo
                //   timeout for another 5 minutes by default, but does not run a
                //   command.  Not all security policies support cached credentials.
                cmd.arg("-v");
            }
            SudoKind::WinSudo => {
                // Windows `sudo` doesn't cache credentials, so we just execute a
                // dummy command - the easiest on Windows is `rem` in cmd.
                // See: https://learn.microsoft.com/en-us/windows/advanced-settings/sudo/
                cmd.args(["cmd.exe", "/c", "rem"]);
            }
            SudoKind::Gsudo => {
                // `gsudo` doesn't have anything like `sudo -v` to cache credentials,
                // so we just execute a dummy command - the easiest on Windows is
                // `rem` in cmd. `-d` tells it to run the command directly, without
                // going through a shell (which could be powershell) first.
                // See: https://gerardog.github.io/gsudo/docs/usage
                cmd.args(["-d", "cmd.exe", "/c", "rem"]);
            }
            SudoKind::Pkexec => {
                // I don't think this does anything; `pkexec` usually asks for
                // authentication every time, although it can be configured
                // differently.
                //
                // See the note for `doas` above.
                //
                // See: https://linux.die.net/man/1/pkexec
                cmd.arg("echo");
            }
            SudoKind::Run0 => {
                // `run0` uses polkit for authentication
                // and thus has the same issues as `pkexec`.
                //
                // See: https://www.freedesktop.org/software/systemd/man/devel/run0.html
                cmd.arg("echo");
            }
            SudoKind::Please => {
                // From `man please`
                //   -w, --warm
                //   Warm the access token and exit.
                cmd.arg("-w");
            }
            SudoKind::Null => unreachable!(),
        }
        cmd.status_checked().wrap_err("Failed to elevate permissions")
    }

    /// Execute a command with `sudo`.
    pub fn execute<S: AsRef<OsStr>>(&self, ctx: &ExecutionContext, command: S) -> Result<Executor> {
        self.execute_opts(ctx, command, SudoExecuteOpts::new())
    }

    /// Execute a command with `sudo`, with custom options.
    pub fn execute_opts<S: AsRef<OsStr>>(
        &self,
        ctx: &ExecutionContext,
        command: S,
        opts: SudoExecuteOpts,
    ) -> Result<Executor> {
        // null sudo is very different, do separately
        if let SudoKind::Null = self.kind {
            if opts.login_shell {
                // TODO: emulate running in a login shell with su/runuser
                return Err(UnsupportedSudo {
                    sudo_kind: self.kind,
                    option: "login_shell",
                }
                .into());
            }
            if opts.user.is_some() {
                // TODO: emulate running as a different user with su/runuser
                return Err(UnsupportedSudo {
                    sudo_kind: self.kind,
                    option: "user",
                }
                .into());
            }

            // NOTE: we ignore preserve_env and set_home, using
            // no sudo effectively preserves these by default

            // run command directly
            return Ok(ctx.execute(command));
        }

        // self.path is only None for null sudo, which we've handled above
        let mut cmd = ctx.execute(self.path.as_ref().unwrap());

        if opts.login_shell {
            match self.kind {
                SudoKind::Sudo => {
                    cmd.arg("-i");
                }
                SudoKind::Gsudo => {
                    // By default, gsudo runs all commands inside a shell. If login_shell
                    // is *not* specified, we add `-d` to run outside of a shell - see below.
                }
                SudoKind::Doas | SudoKind::WinSudo | SudoKind::Pkexec | SudoKind::Run0 | SudoKind::Please => {
                    return Err(UnsupportedSudo {
                        sudo_kind: self.kind,
                        option: "login_shell",
                    }
                    .into());
                }
                SudoKind::Null => unreachable!(),
            }
        } else if let SudoKind::Gsudo = self.kind {
            // The `-d` (direct) flag disables shell detection, running the command directly
            // rather than through the current shell.
            // Additionally, if the current shell is pwsh >= 7.3.0, then not including this
            // gives errors if the command to run has spaces in it: see
            // https://github.com/gerardog/gsudo/issues/297
            cmd.arg("-d");
        }

        match opts.preserve_env {
            SudoPreserveEnv::All => match self.kind {
                SudoKind::Sudo => {
                    cmd.arg("-E");
                }
                SudoKind::Gsudo => {
                    cmd.arg("--copyEV");
                }
                SudoKind::Doas | SudoKind::WinSudo | SudoKind::Pkexec | SudoKind::Run0 | SudoKind::Please => {
                    return Err(UnsupportedSudo {
                        sudo_kind: self.kind,
                        option: "preserve_env",
                    }
                    .into());
                }
                SudoKind::Null => unreachable!(),
            },
            SudoPreserveEnv::Some(vars) => match self.kind {
                SudoKind::Sudo => {
                    cmd.arg(format!("--preserve-env={}", vars.join(",")));
                }
                SudoKind::Run0 => {
                    for env in vars {
                        cmd.arg(format!("--setenv={}", env));
                    }
                }
                SudoKind::Please => {
                    cmd.arg("-a");
                    cmd.arg(vars.join(","));
                }
                SudoKind::Doas | SudoKind::WinSudo | SudoKind::Gsudo | SudoKind::Pkexec => {
                    return Err(UnsupportedSudo {
                        sudo_kind: self.kind,
                        option: "preserve_env_list",
                    }
                    .into());
                }
                SudoKind::Null => unreachable!(),
            },
            SudoPreserveEnv::None => {}
        }

        if opts.set_home {
            match self.kind {
                SudoKind::Sudo => {
                    cmd.arg("-H");
                }
                SudoKind::Doas
                | SudoKind::WinSudo
                | SudoKind::Gsudo
                | SudoKind::Pkexec
                | SudoKind::Run0
                | SudoKind::Please => {
                    return Err(UnsupportedSudo {
                        sudo_kind: self.kind,
                        option: "set_home",
                    }
                    .into());
                }
                SudoKind::Null => unreachable!(),
            }
        }

        if let Some(user) = opts.user {
            match self.kind {
                SudoKind::Sudo => {
                    cmd.args(["-u", user]);
                }
                SudoKind::Doas | SudoKind::Gsudo | SudoKind::Run0 | SudoKind::Please => {
                    cmd.args(["-u", user]);
                }
                SudoKind::Pkexec => {
                    cmd.args(["--user", user]);
                }
                SudoKind::WinSudo => {
                    // Windows sudo is the only one that doesn't have a `-u` flag
                    return Err(UnsupportedSudo {
                        sudo_kind: self.kind,
                        option: "user",
                    }
                    .into());
                }
                SudoKind::Null => unreachable!(),
            }
        }

        cmd.arg(command);

        Ok(cmd)
    }
}

// On unix we use `SudoKind::Sudo`, and on windows `SudoKind::WinSudo`.
// We always define both though, so that we don't have to put
// #[cfg(...)] everywhere.

#[derive(Clone, Copy, Debug, Display, Deserialize)]
#[serde(rename_all = "lowercase")]
#[strum(serialize_all = "lowercase")]
pub enum SudoKind {
    // On unix, "sudo" in the config file means Sudo
    #[cfg(not(windows))]
    Sudo,
    // and WinSudo is skipped, making it unused.
    #[cfg(not(windows))]
    #[expect(unused, reason = "WinSudo is windows-only")]
    #[serde(skip)]
    WinSudo,

    // On unix, Sudo is skipped and unused
    #[cfg(windows)]
    #[expect(unused, reason = "Sudo is unix-only")]
    #[serde(skip)]
    Sudo,
    // and "sudo" in the config file means WinSudo.
    #[cfg(windows)]
    #[serde(rename = "sudo")]
    WinSudo,

    Doas,
    Gsudo,
    Pkexec,
    Run0,
    Please,
    /// A "no-op" sudo, used when topgrade itself is running as root
    Null,
}

impl SudoKind {
    /// Get the name of the "sudo" binary.
    ///
    /// For `SudoKind::WinSudo`, returns the full hardcoded path
    /// instead to ensure we find Windows Sudo rather than gsudo
    /// masquerading as sudo.
    ///
    /// Only returns `None` for `SudoKind::Null`.
    fn binary_name(self) -> Option<&'static str> {
        match self {
            SudoKind::Doas => Some("doas"),
            SudoKind::Sudo => Some("sudo"),
            SudoKind::WinSudo => Some(r"C:\Windows\System32\sudo.exe"),
            SudoKind::Gsudo => Some("gsudo"),
            SudoKind::Pkexec => Some("pkexec"),
            SudoKind::Run0 => Some("run0"),
            SudoKind::Please => Some("please"),
            SudoKind::Null => None,
        }
    }

    /// Find the full path to the "sudo" binary, if it exists on the system.
    fn which(self) -> Option<PathBuf> {
        match self.binary_name() {
            Some(name) => which(name),
            None => None,
        }
    }
}