use std::ffi::OsString;
use std::io::Read;
use std::io::Seek;
use std::io::Write;
use std::os::unix::prelude::OsStrExt;
use std::path::PathBuf;
use std::process::ExitCode;

use clap::{Parser, Subcommand};

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

#[derive(Parser)]
#[command(version, about, long_about = None)] // , multicall(true))]
struct Args {
    #[arg(long)]
    db: Option<PathBuf>,

    #[command(subcommand)]
    command: Command,
}

#[derive(Subcommand)]
enum Command {
    /// initialize a qroject database. you should run this first, and shouldn't need to again.
    Init,

    /// add a project to the qroject database. projects are unique by their name.
    Add {
        /// the name of the project.
        project: String,
        /// the directory at which the project lives.
        dir: OsString,
        /// if the project is on some other computer, the hostname or address of that computer.
        ///
        /// with this set, `qg <proj>` will ssh to that computer and switch into that directory.
        #[arg(long)]
        host: Option<String>,
        /// misc additional information about the project. not used by qroject itself.
        info: Option<String>,
        /// where the project can be found on the wider internet, if anywhere.
        ///
        /// this is mostly useful as notes for homepages, git remotes, etc.
        upstream: Option<String>,
    },

    /// forget a project of the given name.
    ///
    /// this deletes the database row. this does not make changes to any other files. still, be
    /// careful.
    Forget {
        project: String,
    },

    /// print the directory for the given project.
    ///
    /// this is mostly useful as, for example, `$(q dir foo)` as a stand-in for the actual
    /// directory of foo.
    Dir {
        project: String,
    },

    /// print information about the given project.
    Info {
        project: String,
    },

    /// print the project's upstream, if any.
    Upstream {
        project: String,
    },

    /// edit `project`'s record.
    ///
    /// this opens the project's information in vim (not $EDITOR yet sorry). edits to the project
    /// are written back to the database (purusant to the unique name restriction). optional fields
    /// are omitted when null, but can be set by adding a corresponding line in the file.
    Edit {
        project: String,
    },

    /// list all known projects (optionally, with details)
    List {
        #[arg(short, default_value_t = false)]
        verbose: bool,
    },
}

enum CliResult {
    Ok,
    /// a project-specifying command selected a project that doesn't exist
    NotAProject,
    /// a project-specifying command wanted a field that was None
    NoField,
    /// a command that involved disk i/o failed to either i or o.
    IoError,
    /// something happened related to the database
    DbError,
}

impl std::process::Termination for CliResult {
    fn report(self) -> ExitCode {
        match self {
            CliResult::Ok => ExitCode::SUCCESS,
            CliResult::NotAProject => ExitCode::from(1),
            CliResult::NoField => ExitCode::from(2),
            CliResult::IoError => ExitCode::from(3),
            CliResult::DbError => ExitCode::from(4),
        }
    }
}

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);
}

fn print_project_name(p: Project) {
    println!("{}", p.name);
}

fn print_project(p: Project) {
    println!("{}", p.name);
    if p.is_here() {
        println!("  {: <8}: {}", "path", p.dir.display());
    } else if let Some(host) = p.host.as_ref() {
        println!("  {: <8}: {}:{}", "path", host, p.dir.display());
    } else {
        println!("  {: <8}: {}:{}", "path", "<unknown>", p.dir.display());
    }
    if let Some(info) = p.info.as_ref() {
        println!("  {: <8}: {}", "info", info);
    }
    if let Some(upstream) = p.upstream.as_ref() {
        println!("  {: <8}: {}", "upstream", upstream);
    }
}

fn main() -> CliResult {
    let args = Args::parse();

    let dbpath = args.db.clone().unwrap_or_else(|| {
        let mut path = std::env::home_dir().expect("have a homedir");
        path.push(".config");
        path.push("qroject");
        path.push("projects.db");
        path
    });

    match process(args, dbpath) {
        Ok(()) => CliResult::Ok,
        Err(e) => e,
    }
}

fn process(args: Args, dbpath: PathBuf) -> Result<(), CliResult> {

    if let Command::Init = args.command {
        return DbCtx::init(&dbpath).map_err(|e| {
            eprintln!("{e}");
            CliResult::IoError
        });
    }

    let conn = DbCtx::new(&dbpath).map_err(|e| {
        eprintln!("{e}");
        CliResult::IoError
    })?;

    match args.command {
        Command::Init => { Ok(()) /* unreachable */ },
        Command::Add { project, dir, info, upstream, host } => {
            conn.project_add(
                Project {
                    id: 0,
                    name: project,
                    dir,
                    info,
                    upstream,
                    host,
                }
            ).map_err(|e| {
                eprintln!("could not add project: {e}");
                CliResult::DbError
            })
        },

        Command::Forget { project } => {
            conn.project_forget(
                &project,
            ).map_err(|e| {
                eprintln!("could not forget project: {e}");
                CliResult::DbError
            })
        }

        Command::Dir { project } => {
            let proj = conn.project_by_name(&project).map_err(|e| {
                eprintln!("could not look up project: {e}");
                CliResult::DbError
            })?;
            let proj = proj.ok_or(CliResult::NotAProject)?;

            println!("{}", proj.dir.display());
            Ok(())
        }

        Command::Info { project } => {
            let proj = conn.project_by_name(&project).map_err(|e| {
                eprintln!("could not look up project: {e}");
                CliResult::DbError
            })?;
            let proj = proj.ok_or(CliResult::NotAProject)?;

            print_project(proj);
            Ok(())
        }

        Command::Upstream { project } => {
            let proj = conn.project_by_name(&project).map_err(|e| {
                eprintln!("could not look up project: {e}");
                CliResult::DbError
            })?;
            let proj = proj.ok_or(CliResult::NotAProject)?;
            let upstream = proj.upstream.as_ref().ok_or(CliResult::NoField)?;

            println!("{}", upstream);
            Ok(())
        }

        Command::Edit { project } => {
            let proj = conn.project_by_name(&project).map_err(|e| {
                eprintln!("could not look up project: {e}");
                CliResult::DbError
            })?;
            let mut p = proj.ok_or(CliResult::NotAProject)?;

            let mut existing = String::new();
            use std::fmt::{Write as FmtWrite};
            use std::os::fd::FromRawFd;
            writeln!(existing, "name:{}", p.name)
                .expect("can write to a string...");
            writeln!(existing, "dir:{}", p.dir.display())
                .expect("can write to a string...");
            if let Some(host) = p.host.as_ref() {
                writeln!(existing, "host:{}", host)
                    .expect("can write to a string...");
            }
            if let Some(info) = p.info.as_ref() {
                writeln!(existing, "info:{}", info)
                    .expect("can write to a string...");
            }
            if let Some(upstream) = p.upstream.as_ref() {
                writeln!(existing, "upstream:{}", upstream)
                    .expect("can write to a string...");
            }

            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(CliResult::IoError);
            }

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

            let res = file.write_all(existing.as_bytes());
            if let Err(e) = res {
                eprintln!("could not write: {:?}", e);
                return Err(CliResult::IoError);
            }

            let res = match std::process::Command::new("vim")
                .arg(str::from_utf8(&template[..]).expect("valid"))
                .status() {
                Ok(res) => res,
                Err(e) => {
                    eprintln!("failed to exec editor: {:?}", e);
                    return Err(CliResult::IoError);
                }
            };

            if !res.success() {
                return Err(CliResult::IoError);
            }

            let mut edited = String::new();
            if let Err(_e) = file.rewind() {
                return Err(CliResult::IoError);
            }
            if let Err(_e) = file.read_to_string(&mut edited) {
                return Err(CliResult::IoError);
            }

            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 {
                    eprintln!("bogus line: {line}");
                    return Err(CliResult::IoError);
                };
                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 {
                eprintln!("missing name or dir");
                return Err(CliResult::IoError);
            };

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

            conn.project_update(&p)
                .map_err(|e| {
                    eprintln!("failed to update project: {}", e);
                    CliResult::IoError
                })
        }

        Command::List { verbose: details } => {
            let op = if details {
                print_project
            } else {
                print_project_name
            };

            conn.for_each_project(op).map_err(|e| {
                eprintln!("could iterate projects: {e}");
                CliResult::DbError
            })
        }
    }
}