use std::collections::HashMap;

use anyhow::{Context, Result, bail};
use console::Term;
use git2::Oid;
use ngit::{
    client::{
        Client, Connect, Params, fetching_with_report, get_repo_ref_from_cache,
        get_state_from_cache,
    },
    fetch::fetch_from_git_server,
    git::{Repo, RepoActions, nostr_url::NostrUrlDecoded},
    list::{get_ahead_behind, list_from_remotes},
    push::push_to_remote,
    repo_ref::{get_repo_coordinates_when_remote_unknown, is_grasp_server_clone_url},
    repo_state::RepoState,
    utils::{get_short_git_server_name, join_with_and},
};

#[derive(Debug, clap::Args)]
pub struct SubCommandArgs {
    /// optionally just sync a specific reference. eg main or v1.5.2
    #[clap(short, long)]
    pub(crate) ref_name: Option<String>,
    /// force push updates and delete refs from non-grasp git servers
    #[arg(long, action)]
    force: bool,
}

#[allow(clippy::too_many_lines)]
pub async fn launch(args: &SubCommandArgs) -> Result<()> {
    let git_repo = Repo::discover().context("failed to find a git repository")?;
    let git_repo_path = git_repo.get_path()?;

    let full_ref_name = if let Some(ref_name) = &args.ref_name {
        if ref_name.starts_with("refs/") {
            if git_repo.git_repo.find_reference(ref_name).is_ok() {
                Some(ref_name.clone())
            } else {
                bail!("could not find reference {ref_name}");
            }
        } else if git_repo
            .git_repo
            .find_reference(&format!("refs/tags/{ref_name}"))
            .is_ok()
        {
            Some(format!("refs/tags/{ref_name}"))
        } else if git_repo
            .git_repo
            .find_reference(&format!("refs/heads/{ref_name}"))
            .is_ok()
        {
            Some(format!("refs/heads/{ref_name}"))
        } else {
            bail!("could not find reference {ref_name}");
        }
    } else {
        None
    };

    let client = Client::new(Params::with_git_config_relay_defaults(&Some(&git_repo)));

    let (nostr_remote_name, decoded_nostr_url) = git_repo
        .get_first_nostr_remote_when_in_ngit_binary()
        .await.context("failed to list git remotes")?
        .context("no `nostr://` remote detected. `ngit sync` must be run from a repo with a nostr remote")?;

    let repo_coordinate = get_repo_coordinates_when_remote_unknown(&git_repo, &client).await?;

    let _ = fetching_with_report(git_repo_path, &client, &repo_coordinate).await?;

    // TODO push announcement event, then state event to grasps

    let repo_ref = get_repo_ref_from_cache(Some(git_repo_path), &repo_coordinate).await?;

    let nostr_state = get_state_from_cache(Some(git_repo_path), &repo_ref).await?;

    let term = console::Term::stderr();

    let remote_states = list_from_remotes(
        &term,
        &git_repo,
        &repo_ref.git_server,
        &decoded_nostr_url,
        Some(&nostr_state),
    )
    .await;

    let missing_refs =
        fetch_missing_refs(&git_repo, &nostr_state, &remote_states, &decoded_nostr_url);

    for (url, (remote_state, is_grasp_server)) in &remote_states {
        let remote_name = get_short_git_server_name(url);
        let mut refspecs = vec![];
        // delete ref from remote
        let mut not_deleted = vec![];
        for remote_ref_name in remote_state.keys() {
            // skip unspecified refs
            if let Some(full_ref_name) = &full_ref_name {
                if remote_ref_name != full_ref_name {
                    continue;
                }
            }
            if (!remote_ref_name.starts_with("refs/heads/pr/")
                && (remote_ref_name.starts_with("refs/heads/")
                    || remote_ref_name.starts_with("refs/tags/")))
                && !nostr_state
                    .state
                    .keys()
                    .any(|nostr_ref| nostr_ref.eq(remote_ref_name))
            {
                if *is_grasp_server || args.force {
                    // delete branches / tags not on nostr
                    refspecs.push(format!(":{remote_ref_name}"));
                } else {
                    not_deleted.push(remote_ref_name);
                }
            }
        }
        // add or update ref on remote
        let mut not_updated = vec![];
        for nostr_ref_name in nostr_state.state.keys() {
            // skip unspecified refs
            if let Some(full_ref_name) = &full_ref_name {
                if nostr_ref_name != full_ref_name {
                    continue;
                }
            }
            // skip refs missing locally
            if missing_refs.contains(nostr_ref_name) {
                continue;
            }
            // strip refs/heads/ or refs/tags/ prefix to get the tracking ref segment
            // e.g. refs/heads/master -> master, refs/tags/v1.0.0 -> v1.0.0
            let tracking_ref_name = nostr_ref_name
                .strip_prefix("refs/heads/")
                .or_else(|| nostr_ref_name.strip_prefix("refs/tags/"))
                .unwrap_or(nostr_ref_name.as_str());
            if invalid_nostr_state_ref(nostr_ref_name) {
                // ensure nostr_state only supports refs/heads and refs/tags/
                // and not refs/heads/prs/*
            } else if let Some(remote_ref_value) = remote_state.get(nostr_ref_name) {
                // update ref
                let force_required = {
                    if let Ok((ahead, _)) =
                        get_ahead_behind(&git_repo, nostr_ref_name, remote_ref_value)
                    {
                        !ahead.is_empty()
                    } else {
                        true
                    }
                };
                if nostr_state
                    .state
                    .get(nostr_ref_name)
                    .is_none_or(|nostr_ref_value| nostr_ref_value.eq(remote_ref_value))
                {
                    // no action if ref in sync
                } else if remote_ref_value.starts_with("ref ") && !(args.force || *is_grasp_server)
                {
                    // dont try and sync push symbolic refs
                } else if !force_required {
                    refspecs.push(format!(
                        "refs/remotes/{nostr_remote_name}/{tracking_ref_name}:{nostr_ref_name}",
                    ));
                } else if *is_grasp_server || args.force {
                    refspecs.push(format!(
                        "+refs/remotes/{nostr_remote_name}/{tracking_ref_name}:{nostr_ref_name}",
                    ));
                } else {
                    not_updated.push(nostr_ref_name);
                }
            } else {
                // add missing refs
                refspecs.push(format!(
                    "refs/remotes/{nostr_remote_name}/{tracking_ref_name}:{nostr_ref_name}",
                ));
            }
        }

        if refspecs.is_empty() {
            if !not_updated.is_empty() || !not_deleted.is_empty() {
                term.write_line(&format!("{remote_name} in sync excluding"))?;
            } else {
                term.write_line(&format!("{remote_name} already in sync"))?;
            }
            // report already in sync
        } else {
            match push_to_remote(
                &git_repo,
                url,
                &decoded_nostr_url,
                &refspecs,
                &term,
                *is_grasp_server || is_grasp_server_clone_url(url),
                &[],
            ) {
                Err(error) => {
                    term.write_line(&format!(
                        "error pushing updates to {remote_name}: error: {error}"
                    ))?;
                }
                Ok(updated_refs) => {
                    if updated_refs.values().all(std::option::Option::is_none) {
                        if *is_grasp_server || args.force {
                            term.write_line(&format!("{remote_name} sync completed"))?;
                            // TODO we only know if there was an error but not
                            // if it rejected any
                            // updates
                        } else {
                            // we should report on refs not force pushed
                            term.write_line(&format!("{remote_name} sync completed"))?;
                        }
                    } else {
                        term.write_line(&format!(
                            "{remote_name} sync completed but not all changes were accepted"
                        ))?;
                    }
                    for name in &not_deleted {
                        term.write_line(&format!("  - {name} not deleted"))?;
                    }
                    for name in &not_updated {
                        term.write_line(&format!("  - {name} not updated due to conflicts"))?;
                    }
                    if !not_updated.is_empty() || !not_deleted.is_empty() {
                        term.write_line("run `ngit sync --force` to delete refs or overwrite conflicts and potentially lose work")?;
                    }
                }
            }
        }
    }

    if !missing_refs.is_empty() {
        println!(
            "skipped the following refs as could not find them locally or on any git servers: {}",
            join_with_and(&missing_refs)
        );
    }
    Ok(())
}

fn invalid_nostr_state_ref(ref_name: &str) -> bool {
    ref_name.starts_with("refs/heads/pr/")
        && !(ref_name.starts_with("refs/heads/") || ref_name.starts_with("refs/tags/"))
}

fn identify_missing_refs(git_repo: &Repo, state: &HashMap<String, String>) -> Vec<String> {
    let mut missing_oids = vec![];
    for tip in state.values() {
        if let Ok(exist) = git_repo.does_commit_exist(tip) {
            let oid_exists_as_tag = Oid::from_str(tip).is_ok_and(|tip| {
                git_repo
                    .git_repo
                    .find_object(tip, Some(git2::ObjectType::Tag))
                    .is_ok()
            });

            if !exist && !oid_exists_as_tag {
                missing_oids.push(tip.to_string());
            }
        }
    }
    missing_oids
}

/// returns refs that are still missing
fn fetch_missing_refs(
    git_repo: &Repo,
    nostr_state: &RepoState,
    remote_states: &HashMap<String, (HashMap<String, String>, bool)>,
    nostr_url_decoded: &NostrUrlDecoded,
) -> Vec<String> {
    let mut tried_remotes: Vec<String> = vec![];
    let required_oids = identify_missing_refs(git_repo, &nostr_state.state);
    if !required_oids.is_empty() {
        println!("fetching git data missing locally");
    }
    loop {
        let required_oids = identify_missing_refs(git_repo, &nostr_state.state);
        let mut oids_on_remote: HashMap<String, Vec<String>> = HashMap::new();
        if !required_oids.is_empty() {
            for (url, (state, _)) in remote_states {
                if tried_remotes.contains(url) {
                    continue;
                }
                for oid in &required_oids {
                    if state.values().any(|v| v.eq(oid)) {
                        oids_on_remote
                            .entry(url.to_string())
                            .or_default()
                            .push(oid.clone());
                    }
                }
            }
        }
        if let Some((url, oids)) = oids_on_remote.iter().max_by_key(|(url, vec)| {
            if tried_remotes.contains(url) {
                0
            } else {
                vec.len()
            }
        }) {
            if oids.is_empty() || tried_remotes.contains(url) {
                break;
            }
            tried_remotes.push(url.clone());
            let _ = fetch_from_git_server(
                git_repo,
                oids,
                url,
                nostr_url_decoded,
                &Term::stdout(),
                is_grasp_server_clone_url(url),
            );
        } else {
            break;
        }
    }

    let still_missing_oids = identify_missing_refs(git_repo, &nostr_state.state);
    if still_missing_oids.is_empty() {
        vec![]
    } else {
        let missing_refs: Vec<String> = nostr_state
            .state
            .iter()
            .filter_map(|(key, value)| {
                if still_missing_oids.contains(value) {
                    Some(key.clone())
                } else {
                    None
                }
            })
            .collect();
        println!(
            "could not find refs on repo git servers: {}",
            join_with_and(&missing_refs)
        );
        missing_refs
    }
}