//! Hive-wide knowledge repository management.
//!
//! `internal/knowledge` on the forge is cloned to
//! [`LOCAL_DIR`] and bind-mounted read-only into every agent container
//! at `/knowledge`. Agents read documents from it directly and
//! contribute by forking the repo and opening PRs — they never write
//! to the bind-mounted path inside the container.
//!
//! hive-c0re maintains the local clone. It learns that the repository
//! moved from the **swarm controller**, which owns the one Forgejo
//! webhook and addresses an event to each hive over the queue; a
//! periodic pull in `main.rs` provides a fallback cadence.
//!
//! A hive used to register that webhook itself, pointing at its own
//! `/webhook/knowledge`. A webhook has exactly one target URL, so with
//! more than one hive that was last-writer-wins rather than idempotent —
//! every hive but the most recent silently stopped receiving deliveries.
//!
//! The repo itself (public, README-seeded) is the swarm controller's too;
//! this module only clones and pulls it.

use anyhow::{Context, Result};

use crate::coordinator::Coordinator;
use crate::forge::{core_auth_header, forge_git_url};

pub const ORG: &str = "internal";
pub const REPO: &str = "knowledge";

/// Host-side path for the local clone. Also referenced from
/// `lifecycle.rs` (bind-mount source) and the dashboard webhook handler.
/// The literal lives in [`crate::paths`]; re-exported here under the name
/// this module and its consumers have always used.
pub use crate::paths::KNOWLEDGE_DIR as LOCAL_DIR;

/// In-container mount point for the knowledge repo. Bind-mounted
/// read-only from [`LOCAL_DIR`] into every agent container.
pub const CONTAINER_MOUNT: &str = "/knowledge";

/// Clone `internal/knowledge` to [`LOCAL_DIR`] if it is not already a git
/// repository. `core_token` authenticates the HTTPS clone so private repos
/// work. Idempotent — skips if `LOCAL_DIR/.git` exists.
///
/// The swarm controller seeds a README into a freshly created repo. A clone
/// taken before that lands is empty; the next [`pull`] fills it.
///
/// Called once at hive-c0re startup after `forge::ensure_all`.
pub async fn ensure_local_clone(core_token: &str) -> Result<()> {
    let git_dir = std::path::Path::new(LOCAL_DIR).join(".git");
    if git_dir.exists() {
        tracing::debug!("knowledge: local clone already present at {LOCAL_DIR}");
        return Ok(());
    }
    std::fs::create_dir_all(LOCAL_DIR).context("create knowledge local dir")?;
    let url = forge_git_url(&format!("{ORG}/{REPO}"));
    let out = crate::lifecycle::git_command_authed(&core_auth_header(core_token))
        .args(["clone", &url, LOCAL_DIR])
        .output()
        .await
        .context("git clone knowledge repo")?;
    if !out.status.success() {
        let stderr = String::from_utf8_lossy(&out.stderr).trim().to_owned();
        anyhow::bail!("git clone {ORG}/{REPO} failed: {stderr}");
    }
    tracing::info!("knowledge: cloned {ORG}/{REPO} to {LOCAL_DIR}");
    Ok(())
}

/// Current `HEAD` sha of the local clone, best-effort. `None` on any
/// failure (used only to detect whether a pull actually moved `HEAD` —
/// worth skipping the broadcast over, not worth failing the pull for).
async fn head_sha() -> Option<String> {
    let out = tokio::process::Command::new("git")
        .args(["-C", LOCAL_DIR, "rev-parse", "HEAD"])
        .output()
        .await
        .ok()?;
    out.status
        .success()
        .then(|| String::from_utf8_lossy(&out.stdout).trim().to_owned())
}

/// Pull the latest changes in the local clone. Runs only as a
/// `KnowledgePull` job node (see `job_queue::templates::knowledge_pull`),
/// whose resource keeps two pulls off this working tree at once. Uses
/// `--ff-only` so a force-push to the knowledge repo never wedges the local
/// copy silently.
///
/// When the pull actually moves `HEAD` (a real change, not a no-op),
/// broadcasts a short `git diff --stat` summary to every live agent's
/// inbox via `coord` — inbox-only, no forced wake.
pub async fn pull(coord: &Coordinator) -> Result<()> {
    // Sanity: if the clone is missing (e.g. storage was wiped), refuse
    // to pull and let the caller decide whether to re-clone.
    let git_dir = std::path::Path::new(LOCAL_DIR).join(".git");
    if !git_dir.exists() {
        anyhow::bail!("knowledge: {LOCAL_DIR}/.git not found — clone first");
    }
    // Rewrite any credentialed `origin` left by an older clone, which spliced
    // `core:<token>@` into the URL and persisted it in `.git/config` — the one
    // place this repo stored a token in a named remote, against the rule
    // `forge::repos::push_config` states. Harmless to repeat once the URL is
    // already clean.
    let plain = crate::forge::forge_git_url(&format!("{ORG}/{REPO}"));
    let _ = crate::lifecycle::git_command()
        .args(["-C", LOCAL_DIR, "remote", "set-url", "origin", &plain])
        .output()
        .await;
    // Discard any local drift before pulling — both tracked (`reset --hard`)
    // and untracked (`clean -fd`). Nothing in this codebase writes to
    // `LOCAL_DIR` after the initial clone — this working tree exists to mirror
    // `origin/main`, not to be edited in place. A tracked file left dirty
    // by any other means (a stray manual edit on the host, an interrupted
    // prior operation, or two pulls running on this working tree at once)
    // would otherwise abort the `--ff-only` merge below with
    // "local changes would be overwritten"; an untracked file left behind
    // the same ways aborts it with "untracked working tree files would be
    // overwritten" instead — same wedge, just `clean`'s failure message
    // rather than `reset`'s. Either way it wedges every future pull
    // identically until someone notices and resets it by hand. Best-effort:
    // a failure here surfaces through the pull's own error below rather
    // than needing its own branch.
    let _ = crate::lifecycle::git_command()
        .args(["-C", LOCAL_DIR, "reset", "--hard", "HEAD"])
        .output()
        .await;
    let _ = crate::lifecycle::git_command()
        .args(["-C", LOCAL_DIR, "clean", "-fd"])
        .output()
        .await;

    let before = head_sha().await;
    // The repo is public (the swarm controller makes it so), so an
    // unauthenticated pull is enough — but authenticate when a token is around,
    // which keeps this working if the repo is ever made private again.
    let auth = crate::forge::core_token().map(|t| core_auth_header(&t));
    let mut cmd = match &auth {
        Some(header) => crate::lifecycle::git_command_authed(header),
        None => crate::lifecycle::git_command(),
    };
    // Remote and branch are named explicitly. A bare `git pull` merges
    // whatever `branch.<current>.merge` lists, and a clone with more than one
    // such entry aborts with "Cannot fast-forward to multiple branches" —
    // taking /knowledge out across the hive over local config this daemon
    // never writes and cannot see. `origin` exists by construction: the
    // `remote set-url` above just set it.
    let out = cmd
        .args(["-C", LOCAL_DIR, "pull", "--ff-only", "origin", "main"])
        .output()
        .await
        .context("git pull knowledge")?;
    if !out.status.success() {
        let stderr = String::from_utf8_lossy(&out.stderr).trim().to_owned();
        anyhow::bail!("git pull {ORG}/{REPO} failed: {stderr}")
    }
    let stdout = String::from_utf8_lossy(&out.stdout).trim().to_owned();
    tracing::info!(result = %stdout, "knowledge: pull succeeded");

    let after = head_sha().await;
    if let (Some(before), Some(after)) = (before, after)
        && before != after
    {
        broadcast_change(coord, &before, &after).await;
    }
    Ok(())
}

/// Diff `before..after` in the local clone and broadcast a one-line-per-file
/// summary to every live agent. Best-effort — a diff or send failure is
/// logged, never propagated (the pull itself already succeeded).
async fn broadcast_change(coord: &Coordinator, before: &str, after: &str) {
    let diff = tokio::process::Command::new("git")
        .args([
            "-C",
            LOCAL_DIR,
            "diff",
            "--stat",
            &format!("{before}..{after}"),
        ])
        .output()
        .await;
    let stat = match diff {
        Ok(out) if out.status.success() => String::from_utf8_lossy(&out.stdout).trim().to_owned(),
        Ok(out) => {
            let stderr = String::from_utf8_lossy(&out.stderr).trim().to_owned();
            tracing::warn!(%stderr, "knowledge: diff --stat failed; broadcasting without it");
            String::new()
        }
        Err(e) => {
            tracing::warn!(error = ?e, "knowledge: diff --stat failed; broadcasting without it");
            String::new()
        }
    };
    let body = if stat.is_empty() {
        "[system] /knowledge updated — see the repo for what changed.".to_owned()
    } else {
        format!("[system] /knowledge updated:\n{stat}")
    };
    let errors = coord.broadcast_send(hive_sh4re::manager::SYSTEM_SENDER, &body);
    if !errors.is_empty() {
        tracing::warn!(?errors, "knowledge: broadcast had per-agent failures");
    }
}