use bash_builtins::{
    builtin_metadata, Args, Builtin, Error, Result
};

use std::ffi::{CString, OsStr};
use std::sync::{Arc, Mutex, OnceLock};
use std::io::{stdout, stderr, Seek, Read, Write};
use std::path::PathBuf;

#[cfg(target_family="unix")]
use std::os::unix::ffi::OsStrExt;

mod shared;
use shared::{Project, DbCtx};

static QROJECT: OnceLock<Arc<Mutex<core::result::Result<QrojectInner, i32>>>> = OnceLock::new();

struct QrojectGo {
    inner: Arc<Mutex<core::result::Result<QrojectInner, i32>>>,
}

struct QrojectInfo {
    inner: Arc<Mutex<core::result::Result<QrojectInner, i32>>>,
}

struct QrojectDir {
    inner: Arc<Mutex<core::result::Result<QrojectInner, i32>>>,
}

struct Qroject {
   inner: Arc<Mutex<core::result::Result<QrojectInner, i32>>>
}

impl QrojectGo {
    fn new() -> Self {
        Self {
            inner: QrojectInner::new(),
        }
    }
}

impl Builtin for QrojectGo {
    fn call(&mut self, args: &mut Args) -> Result<()> {
        args.no_options()?;
        let mut arg_iter = args.raw_arguments();
        let projname = arg_iter.next()
            .ok_or(Error::ExitCode(1))?
            .to_str()
            .map_err(|_| Error::ExitCode(2))?
            .to_owned();
        drop(arg_iter);
        args.finished()?;

        let mut guard = self.inner.lock().unwrap();
        let handle = guard.as_mut()
            .map_err(|c| Error::ExitCode(*c))?;

        handle.op_go(&projname)
    }
}

impl QrojectInfo {
    fn new() -> Self {
        Self {
            inner: QrojectInner::new(),
        }
    }
}

impl Builtin for QrojectInfo {
    fn call(&mut self, args: &mut Args) -> Result<()> {
        args.no_options()?;
        let mut arg_iter = args.raw_arguments();
        let projname = arg_iter.next()
            .ok_or(Error::ExitCode(1))?
            .to_str()
            .map_err(|_| Error::ExitCode(2))?
            .to_owned();
        drop(arg_iter);
        args.finished()?;

        let mut guard = self.inner.lock().unwrap();
        let handle = guard.as_mut()
            .map_err(|c| Error::ExitCode(*c))?;

        handle.op_info(&projname)
    }
}

impl QrojectDir {
    fn new() -> Self {
        Self {
            inner: QrojectInner::new(),
        }
    }
}

impl Builtin for QrojectDir {
    fn call(&mut self, args: &mut Args) -> Result<()> {
        args.no_options()?;
        let mut arg_iter = args.raw_arguments();
        let projname = arg_iter.next()
            .ok_or(Error::ExitCode(1))?
            .to_str()
            .map_err(|_| Error::ExitCode(2))?
            .to_owned();
        drop(arg_iter);
        args.finished()?;

        let mut guard = self.inner.lock().unwrap();
        let handle = guard.as_mut()
            .map_err(|c| Error::ExitCode(*c))?;

        handle.op_dir(&projname)
    }
}

impl Qroject {
    fn new() -> Self {
        Self {
            inner: QrojectInner::new(),
        }
    }
}

unsafe extern "C" {
    // from libc. no rustix binding..
    fn mkstemp(template: *mut std::ffi::c_char) -> std::ffi::c_int;
    fn perror(msg: *const std::ffi::c_char);

    // from bash
    fn evalstring(
        cmd: *const std::ffi::c_char,
        from_file: *const std::ffi::c_char,
        flags: std::ffi::c_int
    ) -> std::ffi::c_int;
    fn set_working_directory(path: *const std::ffi::c_char);
}

fn project_go_chdir(path: &OsStr) -> Result<()> {
    // do the same mechanics as `cd` as in bash/builtins/cd.def, ish.
    // that is:
    // * `chdir()`,
    // * then set_working_directory,
    // * then set OLDPWD and PWD.

    let prev_pwd = bash_builtins::variables::find_as_string("PWD");

    rustix::process::chdir(path).map_err(|e| {
        let _ = writeln!(stderr(), "chdir fail: {e}");
        Error::ExitCode(5)
    })?;

    unsafe {
        set_working_directory(path.as_bytes().as_ptr() as *const std::ffi::c_char);
    }

    bash_builtins::variables::set("PWD", path.as_bytes())?;
    if let Some(prev_pwd) = prev_pwd {
        bash_builtins::variables::set("OLDPWD", prev_pwd.as_bytes())?;
    }

    Ok(())
}

fn project_go_ssh(host: &str, p: Project) -> Result<()> {
    let command = format!(
        "ssh {} -t 'cd {}; bash'",
        host,
        p.dir.display()
    );
    let cstr = CString::new(command).expect("TODO: it's valid though!");

    // from `builtins/common.h`
    const SEVAL_NOHIST: std::ffi::c_int = 0x004;
    const SEVAL_NOFREE: std::ffi::c_int = 0x008;

    let res = unsafe {
        evalstring(
            cstr.as_bytes().as_ptr() as *const _,
            std::ptr::null(),
            SEVAL_NOHIST | SEVAL_NOFREE,
        )
    };
    if res != 0 {
        let _ = writeln!(stderr(), "could not eval");
        return Err(Error::ExitCode(2));
    }

    Ok(())
}

impl Builtin for Qroject {
    fn call(&mut self, args: &mut Args) -> Result<()> {
        args.no_options()?;
        let mut arg_iter = args.raw_arguments();
        let command = arg_iter.next()
            .ok_or(Error::ExitCode(1))?
            .to_str()
            .map_err(|_| Error::ExitCode(2))?
            .to_owned();

        if command == "init" {
            let path = QrojectInner::dbpath();
            let Some(path) = path else {
                let _ = writeln!(stderr(), "no home dir?");
                return Err(Error::ExitCode(2));
            };

            return match DbCtx::init(path) {
                Ok(()) => Ok(()),
                Err(e) => {
                    eprintln!("could not init db: {e}");
                    Err(Error::ExitCode(3))
                }
            };
        }

        let mut guard = self.inner.lock().unwrap();
        let handle = guard.as_mut()
            .map_err(|c| Error::ExitCode(*c))?;

        let maybe_projname = arg_iter.next()
            .map(|arg| match arg.to_str() {
                Ok(arg) => Ok(arg),
                Err(e) => {
                    let _ = writeln!(stderr(), "failed to read project name: {e:?}");
                    Err(Error::ExitCode(2))
                }
            })
            .transpose()?;

        match command.as_str() {
            "info" => {
                let projname = maybe_projname
                    .ok_or(Error::ExitCode(1))?
                    .to_owned();

                // TODO: check per-command remaining arglists..
                drop(arg_iter);
                args.finished()?;
                handle.op_info(&projname)
            }
            "upstream" => {
                let projname = maybe_projname
                    .ok_or(Error::ExitCode(1))?
                    .to_owned();

                // TODO: check per-command remaining arglists..
                drop(arg_iter);
                args.finished()?;
                handle.op_upstream(&projname)
            }
            "go" => {
                let projname = maybe_projname
                    .ok_or(Error::ExitCode(1))?
                    .to_owned();

                // TODO: check per-command remaining arglists..
                drop(arg_iter);
                args.finished()?;
                handle.op_go(&projname)
            }
            "dir" => {
                let projname = maybe_projname
                    .ok_or(Error::ExitCode(1))?
                    .to_owned();

                // TODO: check per-command remaining arglists..
                drop(arg_iter);
                args.finished()?;
                handle.op_dir(&projname)
            }
            "add" => {
                let projname = maybe_projname
                    .ok_or_else(|| {
                        let _ = writeln!(stderr(), "q add: q add [project] [projdir]");
                        Error::ExitCode(1)
                    })?
                    .to_owned();

                let projdir = arg_iter.next()
                    .ok_or_else(|| {
                        let _ = writeln!(stderr(), "q add: q add [project] [projdir]");
                        Error::ExitCode(1)
                    })?
                    .to_str()
                    .map_err(|_| Error::ExitCode(2))?
                    .to_owned();

                handle.op_add(&projname, &projdir)
            }
            "edit" => {
                let projname = maybe_projname
                    .ok_or(Error::ExitCode(1))?
                    .to_owned();

                handle.op_edit(&projname)
            }
            "forget" => {
                let projname = maybe_projname
                    .ok_or(Error::ExitCode(1))?
                    .to_owned();

                handle.op_forget(&projname)
            }
            "list" => {
                let prefix = if let Some(prefix) = maybe_projname {
                    Some(prefix.to_owned())
                } else {
                    None
                };

                // TODO: check per-command remaining arglists..
                drop(arg_iter);
                args.finished()?;
                handle.op_list(prefix.as_ref().map(|s| s.as_str()))
            }
            other => {
                let _ = writeln!(stderr(), "unknown command: {}", other);
                Err(Error::ExitCode(127))
            }
        }
    }
}

struct QrojectInner {
    // can be None if there's no ~/.config/qroject/
    db: Option<DbCtx>,
}

impl QrojectInner {
    fn dbpath() -> Option<PathBuf> {
        let home = std::env::home_dir();
        home.map(|mut homedir| {
            homedir.push(".config");
            homedir.push("qroject");
            homedir.push("projects.db");
            homedir
        })
    }

    fn new() -> Arc<Mutex<core::result::Result<Self, i32>>> {
        let r = QROJECT.get_or_init(|| {
            let conn = Self::dbpath().as_ref().map(|p| DbCtx::new(p)).transpose();
            let inner = match conn {
                Ok(db) => Ok(QrojectInner { db }),
                Err(e) => {
                    eprintln!("{e}");
                    Err(126)
                }
            };
            Arc::new(Mutex::new(inner))
        });

        Arc::clone(r)
    }

    fn op_go(&mut self, projname: &str) -> Result<()> {
        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        let project = db.project_by_name(&projname)
            .map_err(|e| {
                let _ = writeln!(stderr(), "could not find project: {e}");
                Error::ExitCode(17)
            })?;
        let Some(p) = project else {
            let _ = writeln!(stderr(), "no such project: {}", projname)?;
            return Err(Error::ExitCode(4));
        };

        if p.is_here() {
            project_go_chdir(&p.dir)
        } else if let Some(host) = p.host.clone().as_ref() {
            project_go_ssh(host, p)
        } else {
            let _ = writeln!(stderr(), "don't know how to get to: {}", projname);
            return Err(Error::ExitCode(5));
        }
    }

    fn op_info(&mut self, projname: &str) -> Result<()> {
        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        let project = db.project_by_name(&projname)
            .map_err(|e| {
                let _ = writeln!(stderr(), "could not find project: {e}");
                Error::ExitCode(17)
            })?;
        let Some(p) = project else {
            let _ = writeln!(stderr(), "no such project: {}", projname)?;
            return Err(Error::ExitCode(4));
        };

        let mut w = stdout();
        let _ = writeln!(w, "{}", p.name)?;
        let _ = writeln!(w, "  {: <8}: {}", "path", p.dir.display())?;
        if let Some(info) = p.info.as_ref() {
            let _ = writeln!(w, "  {: <8}: {}", "info", info)?;
        }
        if let Some(upstream) = p.upstream.as_ref() {
            let _ = writeln!(w, "  {: <8}: {}", "upstream", upstream)?;
        }

        Ok(())
    }

    fn op_upstream(&mut self, projname: &str) -> Result<()> {
        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        let project = db.project_by_name(&projname)
            .map_err(|e| {
                let _ = writeln!(stderr(), "could not find project: {e}");
                Error::ExitCode(17)
            })?;
        let Some(p) = project else {
            let _ = writeln!(stderr(), "no such project: {}", projname)?;
            return Err(Error::ExitCode(4));
        };

        let Some(upstream) = p.upstream.as_ref() else {
            return Err(Error::ExitCode(1));
        };

        let mut w = stdout();
        let _ = writeln!(w, "{}", upstream)?;
        Ok(())
    }

    fn op_list(&mut self, prefix: Option<&str>) -> Result<()> {
        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        let print_project_name = |p: Project| {
            if let Some(prefix) = prefix {
                if !p.name.starts_with(prefix) {
                    return;
                }
            }

            let _ = writeln!(stdout(), "{}", p.name);
        };

        db.for_each_project(print_project_name)
            .map_err(|e| {
                let _ = writeln!(stderr(), "could not list projects: {e}");
                Error::ExitCode(2)
            })
    }

    fn op_dir(&mut self, projname: &str) -> Result<()> {
        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        let project = db.project_by_name(&projname)
            .map_err(|e| {
                let _ = writeln!(stderr(), "could not find project: {e}");
                Error::ExitCode(17)
            })?;
        let Some(p) = project else {
            let _ = writeln!(stderr(), "no such project: {}", projname)?;
            return Err(Error::ExitCode(4));
        };

        if let Some(host) = p.host.as_ref() {
            let _ = writeln!(stderr(), "project is at {}, not local", host)?;
            return Err(Error::ExitCode(5));
        }

        let mut w = stdout();
        let _ = writeln!(w, "{}", p.dir.display())?;
        Ok(())
    }

    fn op_forget(&mut self, projname: &str) -> Result<()> {
        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        db.project_forget(&projname)
            .map_err(|e| {
                let _ = writeln!(stderr(), "could not forget {}: {}", projname, e);
                Error::ExitCode(2)
            })?;

        Ok(())
    }

    fn op_edit(&mut self, projname: &str) -> Result<()> {
        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        let project = db.project_by_name(&projname)
            .map_err(|e| {
                let _ = writeln!(stderr(), "could not find project: {e}");
                Error::ExitCode(17)
            })?;
        let Some(mut p) = project else {
            let _ = writeln!(stderr(), "no such project: {}", projname)?;
            return Err(Error::ExitCode(4));
        };

        let mut existing = String::new();
        use std::fmt::{Write as FmtWrite};
        use std::os::fd::FromRawFd;
        writeln!(existing, "name:{}", p.name)
            .map_err(|_| Error::ExitCode(5))?;
        writeln!(existing, "dir:{}", p.dir.display())
            .map_err(|_| Error::ExitCode(5))?;
        if let Some(host) = p.host.as_ref() {
            writeln!(existing, "host:{}", host)
                .map_err(|_| Error::ExitCode(5))?;
        }
        if let Some(info) = p.info.as_ref() {
            writeln!(existing, "info:{}", info)
                .map_err(|_| Error::ExitCode(5))?;
        }
        if let Some(upstream) = p.upstream.as_ref() {
            writeln!(existing, "upstream:{}", upstream)
                .map_err(|_| Error::ExitCode(5))?;
        }

        let mut template: [u8; 18] = *b"/tmp/qrojectXXXXXX";

        let tmpfd = unsafe { mkstemp(template.as_mut_ptr() as *mut std::ffi::c_char) };

        if tmpfd == -1 {
            unsafe { perror(b"mkstemp\0".as_ptr() as *const _); }
            return Err(Error::ExitCode(5));
        }

        let mut file = unsafe { std::fs::File::from_raw_fd(tmpfd) };

        let res = file.write_all(existing.as_bytes());
        if let Err(e) = res {
            writeln!(stderr(), "could not write: {:?}", e)?;
            return Err(Error::ExitCode(6));
        }

        let command = format!(
            "vim {}",
            str::from_utf8(&template[..]).expect("valid")
        );
        let cstr = CString::new(command).expect("TODO: it's valid though!");

        // from `builtins/common.h`
        const SEVAL_NOHIST: std::ffi::c_int = 0x004;
        const SEVAL_NOFREE: std::ffi::c_int = 0x008;

        let res = unsafe {
            evalstring(
                cstr.as_bytes().as_ptr() as *const _,
                std::ptr::null(),
                SEVAL_NOHIST | SEVAL_NOFREE,
            )
        };
        if res != 0 {
            let _ = writeln!(stderr(), "could not eval");
            return Err(Error::ExitCode(2));
        }

        let mut edited = String::new();
        file.rewind()
            .map_err(|_e| Error::ExitCode(5))?;
        file.read_to_string(&mut edited)
            .map_err(|_e| Error::ExitCode(5))?;

        let lines = edited.split("\n");

        let mut new_name = None;
        let mut new_dir = None;
        p.host = None;
        p.info = None;
        p.upstream = None;

        for line in lines {
            if line.trim().is_empty() {
                continue;
            }
            let Some((field, value)) = line.split_once(":") else {
                writeln!(stderr(), "bogus line: {line}")?;
                return Err(Error::ExitCode(7));
            };
            let value = value.to_owned();

            if field == "name" {
                new_name = Some(value);
            } else if field == "dir" {
                new_dir = Some(value);
            } else if field == "host" {
                p.host = Some(value);
            } else if field == "info" {
                p.info = Some(value);
            } else if field == "upstream" {
                p.upstream = Some(value);
            }
        }

        let (Some(name), Some(dir)) = (new_name, new_dir) else {
            writeln!(stderr(), "missing name or dir")?;
            return Err(Error::ExitCode(8));
        };

        p.name = name;
        let dir: &[u8] = dir.as_bytes();
        let dir: &std::ffi::OsStr = OsStrExt::from_bytes(dir);
        p.dir = dir.to_os_string();

        db.project_update(&p)
            .map_err(|e| {
                let _ = writeln!(stderr(), "failed to update project: {}", e);
                Error::ExitCode(9)
            })?;

        std::fs::remove_file(OsStr::from_bytes(&template))
            .map_err(|e| {
                let _ = writeln!(stderr(), "couldn't unlink tempfile? {}", e);
                Error::ExitCode(10)
            })?;

        Ok(())
    }

    fn op_add(&mut self, projname: &str, projdir: &str) -> Result<()> {
        let abspath = std::path::absolute(projdir)
            .map_err(|_| Error::ExitCode(8))?;

        let Some(db) = self.db.as_ref() else {
            return Err(Error::ExitCode(16));
        };

        let new = Project {
            id: 0,
            name: projname.to_string(),
            dir: abspath.into_os_string(),
            info: None,
            upstream: None,
            host: None,
        };
        db.project_add(new)
            .map_err(|e| {
                let _ = writeln!(stderr(), "failed to add project: {}", e);
                Error::ExitCode(9)
            })?;
        Ok(())
    }
}

builtin_metadata!(
    name = "q",
    create = Qroject::new,
    short_doc = "q {add,go,edit,dir,forget, upstream,info,list} [project]",
    long_doc = "project switcher.\n\
    \n\
    switch to, edit, or print information about, a project. all operations\n\
    are either shell built-ins of their own (qg, qi, qd), or subcommands\n\
    of this program, \"q\".\n\
    \n\
    COMMANDS:\n\
    \n  \
      add [projname] [projdir]: add a project named \"projname\" at \n      \
          \"projdir\" to the project database. if this project should \n      \
          have additional fields (like info, upstream, ..) it can be edited\n      \
          after adding.\n  \
      go [projname]: change directory to \"projname\".\n  \
      edit [projname]: edit a project definition in vim (not $EDITOR yet, sorry)\n  \
      dir [projname]: print the directory for \"projname\"\n  \
      upstream [projname]: print the upstream for \"projname\"\n  \
      info [projname]: print all info for \"projname\"\n  \
      forget [projname]: forget about \"projname\". this deletes the row\n      \
          from the database, does not change any other files. still, be careful.\n  \
      list [prefix]: list projects, optionally restricting print all info for \"projname\"\n\
    ",
);

builtin_metadata!(
    name = "qg",
    create = QrojectGo::new,
    short_doc = "qg [project]",
    long_doc = "go to [project]",
);

builtin_metadata!(
    name = "qi",
    create = QrojectInfo::new,
    short_doc = "qi [project]",
    long_doc = "info for [project]",
);

builtin_metadata!(
    name = "qd",
    create = QrojectDir::new,
    short_doc = "qd [project]",
    long_doc = "print directory for [project], if local",
);

// this is probably the kind of software that, circa 2026, you'd ask an LLM to cough up.
// probably would do an ok job of it too, even. see `shoutouts` in the readme for a sense of why i
// didn't. someone put in the work for `bash_builtins`, complete with rather nice docs! i
// appreciate that! in the spirit of collaboration, i wanted to build on that.
//
// stamping out a few thousand lines of emdashful code would not have known about "related
// bindings". try it if you want. there's no love of the game in it. fully spiritless. it's very
// easy to simply Not Care about our peers and neighbors in open source. don't do that. it's
// important to exist, and we only exist if we see each other.
//
// i had fun learning how to put this together and hope you have a bit of fun reading this too. or
// maybe it's just useful, and you never read this; that's ok too.
//
// it's wartful, because of course it is, because *i* coughed this up in basically a day.
// hope you appreciate those too.