use std::{
    fs::OpenOptions,
    io::Write,
    ops::Deref,
    path::{Path, PathBuf},
};

use clap::{Args, Parser, Subcommand};
use config::Config;
use directories::ProjectDirs;
use miette::{miette, Context, IntoDiagnostic, Result};

use temp_dir::TempDir;
use utils::OptExt;

mod utils;

const COVER_LETTER_NAME: &str = "cover-letter";

#[derive(Parser, Debug)]
struct Arg {
    #[arg(
        long,
        global = true,
        help = "git repository to use, defaults to current repository"
    )]
    repo: Option<PathBuf>,
    #[command(subcommand)]
    command: Command,
}

#[derive(Subcommand, Debug)]
enum Command {
    /// Format a patch. alias "p"
    #[command(alias = "p")]
    FormatPatch(FormatPatch),
}

#[derive(Args, Debug)]
struct FormatPatch {
    #[arg(short, long, help = "Branch to use (defaults to the current branch)")]
    branch: Option<String>,
    #[arg(short, long, help = "Jenkins job number")]
    ci: Option<u64>,
    #[arg(
        short,
        long,
        help = "Version of the patchset. Defaults to last patchset + 1"
    )]
    version: Option<u64>,
    #[arg(long, help = "Override the current version of the patchset")]
    force: bool,
    #[arg(long, help = "Silence the CI warning")]
    no_ci: bool,
    #[arg(short, long, help = "Send the patches directly")]
    send: bool,
    #[arg(short, long, help = "Perform the interdiff with the supplied version")]
    diff: Option<u64>,
    #[arg(
        short = 'B',
        long,
        help = "Reference for the interdiff (defaults to origin/master)"
    )]
    base_diff: Option<String>,
    extra_args: Vec<String>,
}

#[derive(Debug, serde::Deserialize)]
struct GsmConfig {
    editor: String,
    repo_url_base: String,
    component: Option<String>,
    ci_url: Option<String>,
    interdiff_base: Option<String>,
}

fn git_bare(args: Vec<&str>) -> Result<String> {
    let out = duct::cmd("git", args)
        .stderr_to_stdout()
        .unchecked()
        .stdout_capture()
        .run()
        .into_diagnostic()
        .wrap_err("failed to launch git")?;

    let output = String::from_utf8_lossy(&out.stdout);
    let output = output.trim();

    if !out.status.success() {
        return Err(miette!("{output}").wrap_err("git command failed"));
    } else {
        Ok(output.to_string())
    }
}

fn main() -> Result<()> {
    let args = Arg::parse();

    let project_dir = ProjectDirs::from("net", "traxys", "git-series-manager")
        .ok_or(miette!("Could not create project dirs"))?;

    let repo_root = args.repo.try_m_unwrap_or_else(|| {
        Ok(PathBuf::from(git_bare(vec![
            "rev-parse",
            "--show-toplevel",
        ])?))
    })?;
    let patch_dir = repo_root.join(".patches");

    let git_cd = |args: &[&str]| {
        let mut a = vec![
            "-C",
            repo_root
                .to_str()
                .ok_or(miette!("{repo_root:?} is not a valid string"))?,
        ];
        a.extend_from_slice(args);

        git_bare(a)
    };

    let config: GsmConfig = Config::builder()
        .add_source(
            config::File::from(project_dir.config_dir().join("config.toml")).required(false),
        )
        .add_source(config::File::from(patch_dir.join("config.toml")).required(false))
        .build()
        .into_diagnostic()
        .wrap_err("Failed to read the configuration")?
        .try_deserialize()
        .into_diagnostic()
        .wrap_err("Failed to deserialize the configuration")?;

    std::fs::create_dir_all(&patch_dir)
        .into_diagnostic()
        .wrap_err("could not create patch directory")?;

    match args.command {
        Command::FormatPatch(args) => {
            if config.ci_url.is_some() && args.ci.is_none() {
                eprintln!("WARNING: CI was not specified\n");
            }

            let branch = args
                .branch
                .try_m_unwrap_or_else(|| Ok(git_cd(&["branch", "--show-current"])?))?;

            let component = config.component.try_m_unwrap_or_else(|| {
                let url = git_cd(&["remote", "get-url", "origin"])?;
                Ok(url
                    .strip_prefix(&config.repo_url_base)
                    .ok_or(miette!(
                        "remote {url} does not start with url base {}",
                        config.repo_url_base
                    ))?
                    .trim_end_matches(".git")
                    .to_string())
            })?;

            println!("Component: {component}");
            println!("Branch: {branch}");

            let ci_link = match (config.ci_url, args.ci) {
                (Some(ci_template), Some(id)) => Some(
                    ci_template
                        .replace("${component}", &component)
                        .replace("${branch}", &branch)
                        .replace("${ci_job}", &id.to_string()),
                ),
                (Some(ci_template), None) => Some(
                    ci_template
                        .replace("${component}", &component)
                        .replace("${branch}", &branch),
                ),
                (None, _) => None,
            };

            let branch_dir = patch_dir.join(&branch);
            std::fs::create_dir_all(&branch_dir)
                .into_diagnostic()
                .wrap_err("could not create branch dir")?;

            let version = match args.version {
                Some(v) => Some(v),
                None => {
                    let mut dir_content = branch_dir
                        .read_dir()
                        .into_diagnostic()
                        .wrap_err("could not read branch dir")?
                        .peekable();

                    match dir_content.peek() {
                        Some(_) => Some(
                            dir_content
                                .into_iter()
                                .filter_map(|e| {
                                    let entry = match e
                                        .into_diagnostic()
                                        .wrap_err("Could not read entry")
                                    {
                                        Ok(e) => e,
                                        Err(e) => return Some(Err(e)),
                                    };

                                    let name = entry.file_name();
                                    let name = name.to_str().expect("patch set entry is not utf8");

                                    if name == "cover-letter" {
                                        None
                                    } else {
                                        Some(Ok(name.parse().expect("version is not an int")))
                                    }
                                })
                                .try_fold(0, |cur, version| -> Result<_> {
                                    let version = version?;

                                    Ok(std::cmp::max(version, cur))
                                })?
                                + 1,
                        ),
                        None => None,
                    }
                }
            };

            let version_dir = branch_dir.join(version.unwrap_or(1).to_string());

            if version_dir.exists() {
                if !args.force {
                    return Err(miette!(
                        "Patch dir {version_dir:?} exists, pass --force to delete it"
                    ));
                } else {
                    std::fs::remove_dir_all(&version_dir).into_diagnostic()?;
                }
            }

            let version_dir = version_dir
                .to_str()
                .ok_or(miette!("Temp dir is not utf-8"))?;

            let format_patch = |extra_args: &[&str]| {
                let mut format_patch_args = vec!["format-patch", "-o", &version_dir];
                let version_str = version.map(|s| s.to_string());

                if let Some(version) = &version_str {
                    format_patch_args.push("-v");
                    format_patch_args.push(version);
                }

                let subject_prefix = format!(r#"--subject-prefix=PATCH {component}"#);
                format_patch_args.extend_from_slice(&[&subject_prefix, "--cover-letter"]);
                format_patch_args.extend_from_slice(extra_args);
                format_patch_args.extend(args.extra_args.iter().map(|s| s.deref()));

                git_cd(&format_patch_args)
            };

            if let Some(interdiff) = args.diff {
                let base = args
                    .base_diff
                    .or(config.interdiff_base)
                    .unwrap_or_else(|| String::from("origin/master"));

                struct TempBranch<'a> {
                    name: &'a str,
                    git: &'a dyn Fn(&[&str]) -> Result<String>,
                }

                impl<'a> Drop for TempBranch<'a> {
                    fn drop(&mut self) {
                        (self.git)(&["branch", "-D", self.name]).unwrap();
                    }
                }

                let branch = {
                    let name = "__patch_old";
                    git_cd(&["branch", name, &base])?;
                    TempBranch { name, git: &git_cd }
                };

                struct GitWorktree {
                    _dir: TempDir,
                    path: String,
                }

                impl GitWorktree {
                    pub fn exec(&self, args: &[&str]) -> Result<String> {
                        let mut a = vec!["-C", &self.path];
                        a.extend_from_slice(args);

                        git_bare(a)
                    }
                }

                impl Drop for GitWorktree {
                    fn drop(&mut self) {
                        self.exec(&["worktree", "remove", &self.path]).unwrap();
                    }
                }

                let wt = {
                    let worktree = temp_dir::TempDir::new()
                        .into_diagnostic()
                        .wrap_err("Could not create worktree directory")?;

                    let worktree_path = worktree
                        .path()
                        .to_str()
                        .ok_or(miette!("Temp dir is not utf-8"))?
                        .to_string();

                    git_cd(&["worktree", "add", "--detach", &worktree_path])?;

                    GitWorktree {
                        path: worktree_path,
                        _dir: worktree,
                    }
                };

                wt.exec(&["switch", branch.name])?;

                let patches = branch_dir
                    .join(&interdiff.to_string())
                    .read_dir()
                    .into_diagnostic()
                    .wrap_err("Could not read interdiff folder")?
                    .map(|e| -> Result<_> {
                        let e = e
                            .into_diagnostic()
                            .wrap_err("Could not read interdiff entry")?;

                        let path = e
                            .path()
                            .to_str()
                            .ok_or(miette!("Interdiff patch path is not utf-8"))?
                            .to_string();

                        match path.contains("cover-letter") {
                            true => Ok(None),
                            false => Ok(Some(path)),
                        }
                    })
                    .filter_map(|e| e.transpose())
                    .collect::<Result<Vec<_>>>()?;
                let mut apply_args = vec!["am"];
                apply_args.extend(patches.iter().map(|s| s.deref()));
                wt.exec(&apply_args)?;

                let interdiff_branch = format!("--interdiff={}", branch.name);
                format_patch(&[&interdiff_branch])?;
            } else {
                format_patch(&[])?;
            }

            let cover_letter = branch_dir.join(COVER_LETTER_NAME);
            if !cover_letter.exists() {
                let mut cover_letter_template = format!("Title: \n\nBranch: {branch}\n");
                if let Some(ci_link) = &ci_link {
                    cover_letter_template += &format!("CI: {ci_link}\n");
                }

                std::fs::write(&cover_letter, cover_letter_template)
                    .into_diagnostic()
                    .wrap_err("Could not write cover letter")?;
            }

            std::process::Command::new(config.editor)
                .arg(&cover_letter)
                .status()
                .into_diagnostic()
                .wrap_err("Could not edit cover letter")?;

            let cover_letter = std::fs::read_to_string(cover_letter)
                .into_diagnostic()
                .wrap_err("Error while reading back the cover letter")?;

            let Some((title, body)) = cover_letter.split_once('\n') else {
                return Err(miette!("Missing title newline"));
            };

            let Some(title) = title.strip_prefix("Title: ") else {
                return Err(miette!("Missing `Title: ` prefix"));
            };

            let mut cover_letter = None;
            for entry in Path::new(version_dir)
                .read_dir()
                .into_diagnostic()
                .wrap_err("Could not read patch directory")?
            {
                let entry = entry
                    .into_diagnostic()
                    .wrap_err("Error while reading patch directory")?;

                if entry
                    .file_name()
                    .as_encoded_bytes()
                    .ends_with(b"cover-letter.patch")
                {
                    cover_letter = Some(entry.file_name());
                }
            }

            let cover_letter = Path::new(version_dir)
                .join(cover_letter.ok_or(miette!("Did not find cover letter in {version_dir}"))?);

            let cover_letter_content = std::fs::read_to_string(&cover_letter)
                .into_diagnostic()
                .wrap_err("Could not read patchset cover letter")?;

            let cover_letter_content = cover_letter_content
                .replace("*** SUBJECT HERE ***", title.trim())
                .replace("*** BLURB HERE ***", body.trim());

            let mut file = OpenOptions::new()
                .write(true)
                .truncate(true)
                .open(cover_letter)
                .into_diagnostic()
                .wrap_err("Could not re-open cover letter")?;
            file.write(cover_letter_content.as_bytes())
                .into_diagnostic()
                .wrap_err("Could not save cover letter")?;

            Ok(())
        }
    }
}