//! The review classifier's forge account, [`LOGIN`]: created here with the
//! admin API and given one token, stored at
//! `swarm_secret_client::review_classifier::forge_token_path`. Requesting
//! this account as a reviewer starts a classifier run, and this daemon posts
//! the result as the account's review (`crate::review_classifier::review`).
//! The classifier itself never holds the token.
//!
//! The account gets no repo access here. A repo admin adds it to a repo by
//! hand: read to request it as a reviewer, write (or a place on the branch
//! protection's approvals whitelist) for its approval to count.
//!
//! The token decision is [`super::agent_token`]'s, under this module's name
//! and scopes, so a stored token the forge still lists with the same last
//! eight characters and scopes is kept, and a pass whose reads fail queues
//! nothing.

use std::sync::Arc;

use anyhow::{Context, Result, bail};
use forgejo_api::structs::{CreatePullReviewOptions, RepoSearchQuery};
use forgejo_api::{Auth, Forgejo};
use swarm_secret_client::forge;
use swarm_secret_client::review_classifier::forge_token_path;

use super::Client;
use super::agent_token::{Decision, Observed, classify_named};

/// The classifier's forge login: the reviewer someone requests.
pub const LOGIN: &str = "review-classifier";

/// The forge's name for the account's one token.
pub const TOKEN_NAME: &str = "swarm-review-classifier";

/// What the token may do: post reviews, which the forge files under the
/// repository scope. Which repos is the account's access, granted by hand.
pub const TOKEN_SCOPES: &str = "write:repository";

/// How often [`spawn`] re-checks the account and its token.
const RECONCILE_INTERVAL: std::time::Duration = std::time::Duration::from_mins(5);

/// The email this module creates the account with, and the one it requires
/// before acting on an account named [`LOGIN`]. Under its own domain, so it
/// equals no agent's or hive's account email.
const EMAIL: &str = "review-classifier@services.hyperhive.local";

/// Whether a pass that found `seen` queues a `MintClassifierForgeToken` job.
/// [`Observed::Unknown`] never does, so a forge or store outage can't rotate
/// the token, and neither does a [`Decision::Conflict`], which the job would
/// refuse.
pub fn needs_job(seen: Observed) -> bool {
    matches!(
        seen,
        Observed::NoForgeUser | Observed::Decided(Decision::Mint(_))
    )
}

/// One review as the classifier's account posts it.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Review {
    /// `APPROVED`, `REQUEST_CHANGES` or `COMMENT`.
    pub event: &'static str,
    pub body: String,
}

impl Client {
    /// Make sure [`LOGIN`] exists and holds a live [`TOKEN_NAME`] token in
    /// the store, minting one when it does not. The whole job of the
    /// `MintClassifierForgeToken` node.
    ///
    /// # Errors
    /// When the store or the forge refuses a step, when an account named
    /// [`LOGIN`] exists with another email, or when the read-back does not
    /// show the new token.
    pub async fn ensure_classifier_forge_token(&self) -> Result<()> {
        let path = forge_token_path()?;
        self.ensure_classifier_user().await?;
        let store = crate::store::connect()
            .await
            .context("logging in to the swarm secret store")?;
        let (stored, listed) = self.read_classifier_token(&store, &path).await?;
        let reason = match classify_named(TOKEN_NAME, TOKEN_SCOPES, stored.as_ref(), &listed) {
            Decision::Keep => {
                tracing::debug!("review classifier forge token is current; left as it is");
                return Ok(());
            }
            Decision::Conflict => bail!(
                "the forge lists more than one {TOKEN_NAME:?} token for {LOGIN:?}; delete them \
                 by id and re-run"
            ),
            Decision::Mint(reason) => reason,
        };
        let credential = self
            .replace_token(&store, LOGIN, TOKEN_NAME, TOKEN_SCOPES, &listed, &path)
            .await?;

        Forgejo::new(Auth::Token(&credential.value), self.url.clone())
            .context("building a forge client with the new token")?
            .repo_search(RepoSearchQuery::default())
            .await
            .with_context(|| format!("using {LOGIN}'s new forge token"))?;
        let (stored, listed) = self.read_classifier_token(&store, &path).await?;
        let now = classify_named(TOKEN_NAME, TOKEN_SCOPES, stored.as_ref(), &listed);
        if now != Decision::Keep {
            bail!("{LOGIN}'s new forge token does not read back as current: {now:?}");
        }
        tracing::info!(?reason, %path, "review classifier forge token minted and stored");
        Ok(())
    }

    /// Post `review` on PR `number` of `owner/repo` as [`LOGIN`], on
    /// `commit` when one is given. Reads the token from the store on every
    /// call. The posted review's URL, when the forge names one.
    ///
    /// # Errors
    /// When the store holds no token yet, or the forge refuses the review.
    pub async fn post_classifier_review(
        &self,
        owner: &str,
        repo: &str,
        number: i64,
        commit: Option<&str>,
        review: Review,
    ) -> Result<Option<String>> {
        let path = forge_token_path()?;
        let store = crate::store::connect()
            .await
            .context("logging in to the swarm secret store")?;
        let Some(credential) = store
            .read_optional::<forge::Credential>(&path)
            .await
            .with_context(|| format!("reading {path}"))?
        else {
            bail!("nothing at {path}: the classifier's forge token is not minted yet");
        };
        Forgejo::new(Auth::Token(&credential.value), self.url.clone())
            .context("building a forge client with the classifier's token")?
            .repo_create_pull_review(
                owner,
                repo,
                number,
                CreatePullReviewOptions {
                    body: Some(review.body),
                    comments: None,
                    commit_id: commit.map(str::to_owned),
                    event: Some(review.event.to_owned()),
                },
            )
            .await
            .with_context(|| format!("posting {LOGIN}'s review on PR {number} of {owner}/{repo}"))
            .map(|posted| posted.html_url.map(String::from))
    }

    /// The stored token at `path` and every token the forge lists for
    /// [`LOGIN`], which must exist.
    async fn read_classifier_token(
        &self,
        store: &swarm_secret_client::SecretStore,
        path: &str,
    ) -> Result<(
        Option<forge::Credential>,
        Vec<forgejo_api::structs::AccessToken>,
    )> {
        let stored = store
            .read_optional(path)
            .await
            .with_context(|| format!("reading {path}"))?;
        let Some(listed) = self.list_agent_tokens(LOGIN).await? else {
            bail!("the forge has no user {LOGIN:?} after this job created it");
        };
        Ok((stored, listed))
    }

    /// Create [`LOGIN`] if there is none, refuse one with another email, and
    /// lock it out of creating repos.
    async fn ensure_classifier_user(&self) -> Result<()> {
        self.create_user(LOGIN, EMAIL).await?;
        let user = self
            .api
            .user_get(LOGIN)
            .await
            .with_context(|| format!("read forge user {LOGIN}"))?;
        if user.email.as_deref() != Some(EMAIL) {
            bail!(
                "forge account `{LOGIN}` exists but is not the review classifier's (email {:?}, \
                 expected `{EMAIL}`); refusing to mint a token for it",
                user.email
            );
        }
        self.api
            .admin_edit_user(LOGIN, super::repo_creation_lockdown(LOGIN))
            .await
            .with_context(|| format!("disable repo creation for forge user {LOGIN}"))?;
        Ok(())
    }

    /// What the store and the forge say about the account's token.
    async fn observe_classifier(&self) -> Result<Observed> {
        let path = forge_token_path()?;
        let store = crate::store::connect()
            .await
            .context("logging in to the swarm secret store")?;
        let stored = match store.read_optional::<forge::Credential>(&path).await {
            Ok(stored) => stored,
            Err(e) => {
                tracing::warn!(error = %e, "review classifier forge token: store read failed");
                return Ok(Observed::Unknown);
            }
        };
        Ok(match self.list_agent_tokens(LOGIN).await {
            Ok(Some(listed)) => Observed::Decided(classify_named(
                TOKEN_NAME,
                TOKEN_SCOPES,
                stored.as_ref(),
                &listed,
            )),
            Ok(None) => Observed::NoForgeUser,
            Err(e) => {
                tracing::warn!(error = %format!("{e:#}"), "review classifier forge token: forge read failed");
                Observed::Unknown
            }
        })
    }
}

/// Check the account now and every [`RECONCILE_INTERVAL`] after, and call
/// `enqueue`, which inserts a `MintClassifierForgeToken` node, when it needs
/// a job. A pass that fails is logged and retried on the next tick.
pub fn spawn(client: Arc<Client>, enqueue: impl Fn() + Send + 'static) {
    tokio::spawn(async move {
        let mut ticker = tokio::time::interval(RECONCILE_INTERVAL);
        loop {
            ticker.tick().await;
            let Some(outcome) = super::within_forge_deadline(
                "review classifier forge token",
                client.observe_classifier(),
            )
            .await
            else {
                continue;
            };
            match outcome {
                Ok(seen) if needs_job(seen) => {
                    tracing::info!(?seen, "review classifier forge token: queueing a job");
                    enqueue();
                }
                Ok(seen) => tracing::debug!(?seen, "review classifier forge token: no job"),
                Err(e) => tracing::warn!(
                    error = %format!("{e:#}"),
                    retry_in_s = RECONCILE_INTERVAL.as_secs(),
                    "review classifier forge token: pass failed; retrying next tick"
                ),
            }
        }
    });
}

#[cfg(test)]
mod tests {
    use super::super::agent_token::MintReason;
    use super::*;

    #[test]
    fn the_token_writes_repositories_and_nothing_else() {
        assert_eq!(TOKEN_SCOPES, "write:repository");
        assert_ne!(TOKEN_NAME, super::super::agent_token::AGENT_TOKEN_NAME);
        assert_ne!(TOKEN_NAME, super::super::hive_token::HIVE_TOKEN_NAME);
    }

    #[test]
    fn a_mint_or_a_missing_account_queues_and_nothing_else_does() {
        assert!(needs_job(Observed::NoForgeUser));
        assert!(needs_job(Observed::Decided(Decision::Mint(
            MintReason::NotStored
        ))));
        assert!(!needs_job(Observed::Decided(Decision::Keep)));
        assert!(!needs_job(Observed::Decided(Decision::Conflict)));
        assert!(!needs_job(Observed::Unknown));
    }

    #[test]
    fn the_accounts_email_is_no_agents() {
        assert_ne!(EMAIL, super::super::agent_email(LOGIN));
        assert_ne!(EMAIL, super::super::legacy_agent_email(LOGIN));
    }

    /// An existing account named like the classifier with an agent's email
    /// is refused before the lockdown, so no token is minted for it.
    #[tokio::test]
    async fn the_job_refuses_an_account_that_is_not_the_classifiers() {
        use super::super::tests::{lockdown_patch, stub_forge};

        let (client, seen) = stub_forge(
            (409, r#"{"message":"user already exists"}"#),
            (200, r#"{"email":"review-classifier@hyperhive.local"}"#),
            (200, "{}"),
        )
        .await;
        let err = client
            .ensure_classifier_user()
            .await
            .expect_err("an agent's account is not the classifier's");
        assert!(format!("{err:#}").contains("not the review classifier's"));
        assert!(lockdown_patch(&seen, LOGIN).is_none());
    }

    #[tokio::test]
    async fn the_job_locks_down_the_classifiers_own_account() {
        use super::super::tests::{lockdown_patch, stub_forge};

        let (client, seen) = stub_forge(
            (409, r#"{"message":"user already exists"}"#),
            (
                200,
                r#"{"email":"review-classifier@services.hyperhive.local"}"#,
            ),
            (200, "{}"),
        )
        .await;
        client
            .ensure_classifier_user()
            .await
            .expect("the classifier's own account");
        let body = lockdown_patch(&seen, LOGIN).expect("no lockdown PATCH sent");
        assert_eq!(body["max_repo_creation"], 0);
    }
}