//! The bundle manifest — "what to install", resolved at run time.
//!
//! PLAN.md §7.1: **the bundle is the compat matrix.** CI names one exact, protocol-checked pair of
//! sidecar + overlay versions and commits it to this repo under `bundles/`; the installer fetches
//! it anonymously and installs *that pair*, rather than hardcoding versions or taking each repo's
//! newest release and hoping the two agree.
//!
//! Two consequences show up directly in this module:
//!
//! - **No protocol version is hardcoded anywhere** (§7.4). The number is read from the bundle and
//!   cross-checked against the overlay's own `manifest.json` at deploy time.
//! - **`schema` is not `protocol`.** It versions the shape of this document and moves
//!   independently of both components' versions; a bundle from a newer CI is refused rather than
//!   half-understood.

use anyhow::{bail, Context, Result};
use serde::{Deserialize, Serialize};
use std::collections::BTreeMap;

/// Bundles are plain files in this repo, served by Gitea's raw endpoint over anonymous HTTPS —
/// the shard host has no Gitea account and needs no git client (PLAN.md §1, §7.1).
const BUNDLE_BASE: &str =
    "https://gitea.whitlocktech.com/RunicGateway/installer/raw/branch/main/bundles";

/// The only `schema` this build understands.
const SUPPORTED_SCHEMA: u32 = 1;

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct Bundle {
    pub schema: u32,
    /// The bundle tag, a UTC date, possibly suffixed (`2026.08.04.2`) when a day has two.
    pub bundle: String,
    pub generated: String,
    /// The wire protocol both halves were checked to agree on.
    pub protocol: u32,
    pub link: LinkComponent,
    pub overlay: OverlayComponent,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct LinkComponent {
    pub repo: String,
    pub tag: String,
    pub version: String,
    pub protocol: u32,
    /// Keyed by platform (`linux-x86_64`, `linux-aarch64`, `windows-x86_64`) — link publishes a
    /// binary per target and the installer runs on each, so a single hash could only ever describe
    /// one of them. The set grows over time, so a bundle is not expected to carry every key this
    /// binary knows about: an older one pinned with `--bundle` predates arm64 entirely.
    pub assets: BTreeMap<String, Asset>,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct OverlayComponent {
    pub repo: String,
    pub tag: String,
    pub version: String,
    pub commit: String,
    pub protocol: u32,
    pub servuo: ServUoCompat,
    /// One tarball, platform-independent: the overlay is C# source that ServUO compiles at boot.
    pub asset: Asset,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct ServUoCompat {
    /// The oldest ServUO the *base* overlay is known good on. It only adds files.
    pub min_version: String,
    /// The single ServUO version the *patch tier* was written and verified against (§2.2).
    pub patches_verified_against: String,
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct Asset {
    pub name: String,
    pub url: String,
    pub sha256: String,
}

impl Bundle {
    /// The bundle's own asset for the platform this binary is running on.
    ///
    /// Installing the sidecar is Phase 2, but the lookup lives here so that a run on a platform the
    /// bundle has no binary for fails while resolving — before anything has been written into a
    /// ServUO tree — rather than after the overlay is already deployed.
    pub fn sidecar_asset(&self) -> Result<&Asset> {
        let key = platform_key()?;
        self.link.assets.get(key).ok_or_else(|| {
            anyhow::anyhow!(
                "bundle {} has no uo-link binary for {key} (it has: {}).\n\
                 Bundles published before uo-link built for this platform cannot gain one \
                 retroactively — they are kept unchanged so `--bundle` stays reproducible. \
                 Run without `--bundle` to take the current one.",
                self.bundle,
                self.link
                    .assets
                    .keys()
                    .cloned()
                    .collect::<Vec<_>>()
                    .join(", ")
            )
        })
    }
}

/// The platform key used by `link.assets`, matching the names the bundle CI assigns.
pub fn platform_key() -> Result<&'static str> {
    match (std::env::consts::OS, std::env::consts::ARCH) {
        ("linux", "x86_64") => Ok("linux-x86_64"),
        // Ampere/Graviton and Pi-class hosts (PLAN.md §5.2). Linux only: the shard dials the
        // sidecar out on loopback, so the pair has to be co-located, and no ServUO host is a
        // Windows-on-arm box or a Mac.
        ("linux", "aarch64") => Ok("linux-aarch64"),
        ("windows", "x86_64") => Ok("windows-x86_64"),
        // Naming the platforms that do exist beats failing later with a missing-key error that
        // reads like a corrupt bundle.
        (os, arch) => bail!(
            "no Runic Gateway build exists for {os}/{arch}. \
             The released components target linux-x86_64, linux-aarch64 and windows-x86_64."
        ),
    }
}

/// URL of the current bundle, or of a specific one when `--bundle <tag>` pins it.
pub fn url_for(tag: Option<&str>) -> String {
    match tag {
        Some(tag) => format!("{BUNDLE_BASE}/bundle-{tag}.json"),
        None => format!("{BUNDLE_BASE}/current.json"),
    }
}

/// Fetches and validates a bundle.
pub fn fetch(tag: Option<&str>) -> Result<(Bundle, String)> {
    let url = url_for(tag);
    let body = crate::net::get_text(&url).with_context(|| match tag {
        Some(tag) => format!(
            "cannot read bundle {tag}. Every published bundle is kept forever, so check the tag \
             against {BUNDLE_BASE}/"
        ),
        None => "cannot read the current bundle manifest".to_string(),
    })?;
    let bundle = parse(&body)?;
    Ok((bundle, url))
}

/// Parses a bundle document and applies the checks that must hold before anything is downloaded.
pub fn parse(body: &str) -> Result<Bundle> {
    let bundle: Bundle = serde_json::from_str(body)
        .context("the bundle manifest is not in the shape this installer understands")?;

    if bundle.schema != SUPPORTED_SCHEMA {
        bail!(
            "bundle {} declares schema {} and this installer understands {SUPPORTED_SCHEMA}. \
             Update the installer — the bundle format changed.",
            bundle.bundle,
            bundle.schema
        );
    }

    // Gate 1 already ran in CI (§7.1), where a mismatch stops a bundle from being published at all.
    // Re-checking here costs nothing and covers the case CI cannot: a hand-edited or truncated
    // manifest that never went through the compose job.
    if bundle.link.protocol != bundle.overlay.protocol || bundle.protocol != bundle.link.protocol {
        bail!(
            "bundle {} is internally inconsistent: bundle protocol {}, sidecar {}, overlay {}. \
             A mismatched pair is rejected by the sidecar with 409 rather than mis-parsed, so this \
             is refused here.",
            bundle.bundle,
            bundle.protocol,
            bundle.link.protocol,
            bundle.overlay.protocol
        );
    }

    if bundle.overlay.asset.url.is_empty() || bundle.overlay.asset.sha256.is_empty() {
        bail!(
            "bundle {} names an overlay asset with no URL or checksum",
            bundle.bundle
        );
    }

    Ok(bundle)
}

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

    /// The first published bundle, verbatim from `bundles/current.json`. Using the real document
    /// rather than a hand-written stand-in is the point: it is what CI actually emits.
    const CURRENT: &str = include_str!("../bundles/current.json");

    #[test]
    fn the_published_bundle_parses() {
        let bundle = parse(CURRENT).unwrap();
        assert_eq!(bundle.schema, 1);
        assert_eq!(bundle.bundle, "2026.08.04");
        assert_eq!(bundle.protocol, 3);
        assert_eq!(bundle.link.version, "1.1.0");
        assert_eq!(bundle.overlay.version, "0.1.1");
        assert_eq!(bundle.overlay.servuo.patches_verified_against, "57.4");
        assert!(bundle.overlay.asset.name.ends_with(".tar.gz"));
    }

    #[test]
    fn every_platform_the_bundle_names_is_well_formed() {
        // A floor, not an exact count: `linux-aarch64` joins these from link's first arm64 release
        // (PLAN.md §5.2), and a test asserting "exactly two" would fail on the bundle that adds it
        // rather than on anything being wrong.
        let bundle = parse(CURRENT).unwrap();
        for required in ["linux-x86_64", "windows-x86_64"] {
            let asset = bundle
                .link
                .assets
                .get(required)
                .unwrap_or_else(|| panic!("bundle carries no {required} binary"));
            assert_eq!(asset.sha256.len(), 64);
            assert!(asset.url.contains(&bundle.link.tag));
        }
    }

    #[test]
    fn the_hosts_binary_either_resolves_or_says_why_not() {
        // On x86_64 the lookup must resolve — a bundle missing the host's binary would otherwise
        // fail an install after the overlay had already been deployed. On a host whose platform
        // postdates the bundle (an arm64 box reading the first published one), it must fail with
        // the reason, since every bundle is kept unchanged forever so `--bundle` stays
        // reproducible and therefore cannot gain a key retroactively.
        let bundle = parse(CURRENT).unwrap();
        match bundle.sidecar_asset() {
            Ok(asset) => {
                assert_eq!(asset.sha256.len(), 64);
                assert!(asset.url.contains(&bundle.link.tag));
            }
            Err(e) => {
                let msg = e.to_string();
                assert!(msg.contains(platform_key().unwrap()), "{msg}");
                assert!(msg.contains("--bundle"), "{msg}");
            }
        }
    }

    #[test]
    fn the_host_is_a_platform_the_components_are_built_for() {
        // `cargo test` running at all means the host is one the crate compiles on, so a refusal
        // here is a build target the release workflows have not caught up with.
        let key = platform_key().unwrap();
        assert!(
            ["linux-x86_64", "linux-aarch64", "windows-x86_64"].contains(&key),
            "unexpected platform key {key}"
        );
    }

    #[test]
    fn a_newer_schema_is_refused_rather_than_guessed_at() {
        let body = CURRENT.replace("\"schema\": 1", "\"schema\": 2");
        let err = parse(&body).unwrap_err().to_string();
        assert!(err.contains("schema 2"), "{err}");
    }

    #[test]
    fn a_protocol_disagreement_inside_one_bundle_is_refused() {
        // Exactly what CI's gate 1 exists to prevent; re-checked here for documents that never
        // went through it.
        let body = CURRENT.replacen("\"protocol\": 3", "\"protocol\": 4", 2);
        let err = parse(&body).unwrap_err().to_string();
        assert!(err.contains("internally inconsistent"), "{err}");
    }

    #[test]
    fn the_pinned_and_current_urls_differ() {
        assert!(url_for(None).ends_with("/current.json"));
        assert!(url_for(Some("2026.08.04")).ends_with("/bundle-2026.08.04.json"));
    }
}