//! This hive's reads of `internal/meta` and of an agent's config head, as
//! [`crate::meta_rev::MetaSource`], under the hive's forge read token.

use forgejo_api::structs::RepoGetRawFileQuery;
use forgejo_api::{ApiErrorKind, Forgejo, ForgejoError};
use reqwest::StatusCode;

use super::reader::ReaderToken;
use super::{CONFIG_ORG, bounded};
use crate::meta_rev::MetaSource;

/// The org and repo the swarm commits its meta flake to.
const META_OWNER: &str = "internal";
const META_REPO: &str = "meta";

/// The branch an agent's config is deployed from, which `fetch_forge_main`
/// and the swarm controller's pins both read.
const CONFIG_BRANCH: &str = "main";

/// [`MetaSource`] over the forge API.
pub(crate) struct ForgeSource {
    api: Forgejo,
}

/// A source reading as this hive, or `None` when it holds no forge token.
pub(crate) async fn internal_meta_source() -> Option<ForgeSource> {
    let token: ReaderToken = super::reader_token().await?;
    match token.api() {
        Ok(api) => Some(ForgeSource { api }),
        Err(e) => {
            tracing::warn!(error = ?e, "internal/meta: cannot build a forge client");
            None
        }
    }
}

fn is_not_found(e: &ForgejoError) -> bool {
    match e {
        ForgejoError::ApiError(api) => match api.error_kind() {
            ApiErrorKind::NotFound { .. } => true,
            ApiErrorKind::Other(s) => *s == StatusCode::NOT_FOUND,
            _ => false,
        },
        ForgejoError::UnexpectedStatusCode(s) => *s == StatusCode::NOT_FOUND,
        _ => false,
    }
}

impl ForgeSource {
    /// The head commit of `branch` in `owner/repo`; `None` when the repo or
    /// the branch is not there.
    async fn branch_head(
        &self,
        owner: &str,
        repo: &str,
        branch: &str,
    ) -> anyhow::Result<Option<String>> {
        let op = format!("read branch {branch} of {owner}/{repo}");
        match bounded(&op, self.api.repo_get_branch(owner, repo, branch)).await? {
            Ok(branch) => Ok(branch.commit.and_then(|c| c.id)),
            Err(e) if is_not_found(&e) => Ok(None),
            Err(e) => Err(anyhow::Error::new(e).context(op)),
        }
    }
}

impl MetaSource for ForgeSource {
    fn nix_can_fetch(&self) -> bool {
        super::core_token().is_some()
    }

    async fn meta_head(&self) -> anyhow::Result<Option<String>> {
        use anyhow::Context as _;

        let op = format!("read repo {META_OWNER}/{META_REPO}");
        let repo = match bounded(&op, self.api.repo_get(META_OWNER, META_REPO)).await? {
            Ok(repo) => repo,
            Err(e) if is_not_found(&e) => return Ok(None),
            Err(e) => return Err(anyhow::Error::new(e).context(op)),
        };
        if repo.empty.unwrap_or(false) {
            return Ok(None);
        }
        let branch = repo
            .default_branch
            .with_context(|| format!("{META_OWNER}/{META_REPO} names no default branch"))?;
        self.branch_head(META_OWNER, META_REPO, &branch).await
    }

    async fn flake_at(&self, rev: &str) -> anyhow::Result<String> {
        let op = format!("read flake.nix of {META_OWNER}/{META_REPO} at {rev}");
        let query = RepoGetRawFileQuery {
            r#ref: Some(rev.to_owned()),
        };
        let raw = bounded(
            &op,
            self.api
                .repo_get_raw_file(META_OWNER, META_REPO, "flake.nix", query),
        )
        .await?
        .map_err(|e| anyhow::Error::new(e).context(op))?;
        Ok(String::from_utf8_lossy(&raw).into_owned())
    }

    async fn config_head(&self, agent: &str) -> anyhow::Result<Option<String>> {
        self.branch_head(CONFIG_ORG, agent, CONFIG_BRANCH).await
    }
}