cratefield-core 0.3.1

//! The module contract (architecture section 4). A module is a crate that
//! contributes one router under `/v1/<name>`, its migrations, its events and
//! its scheduled work — and sees nothing but ports.

use crate::config::{Config, ConfigError};
use crate::events::{AnyError, EventBus, EventHandler, EventName};
use crate::ports::{Port, Ports};
use crate::surface::Surface;
use crate::template::TemplateRegistry;
use crate::venture::Venture;
use std::sync::Arc;

pub use futures_core::future::BoxFuture;

/// Contract version shared by core and every module. `Harness::build`
/// rejects modules whose `harness_api` differs. Bumped only on breaking
/// contract changes; `cratefield-core`'s major follows it.
pub const HARNESS_API: u32 = 1;

/// The message `Harness::build` and `fz doctor` report for a module whose
/// [`Module::harness_api`] differs from core's: it names the module, the
/// module crate's version, the API it targets, and the `cratefield-core`
/// crate with its version and API (issue #17).
#[must_use]
pub fn harness_api_mismatch(module: &dyn Module) -> String {
    format!(
        "module `{name}` v{version} targets harness API {api}, but {core} v{core_version} \
         provides harness API {harness_api}: rebuild `{name}` against this core — the supported \
         ranges are in docs/COMPATIBILITY.md",
        name = module.name(),
        version = module.version(),
        api = module.harness_api(),
        core = env!("CARGO_PKG_NAME"),
        core_version = env!("CARGO_PKG_VERSION"),
        harness_api = HARNESS_API,
    )
}

/// One migration step, embedded with `include_str!` from
/// `crates/<module>/migrations/<dialect>/NNNN_name.sql` (issue #8).
#[derive(Debug, Clone)]
pub struct SqlMigration {
    /// Sortable id: `0001`, `0002`, ... — zero-padded so lexical order is
    /// apply order.
    pub id: &'static str,
    /// Short slug from the file name (`0001_init.sql` -> `init`), used in
    /// the wrangler-facing collected file names.
    pub name: &'static str,
    pub sql: &'static str,
}

/// The sha256 of a migration's SQL, lowercase hex. Recorded in
/// `harness_migrations` when the migration is applied, so a later run
/// can tell "already applied" from "applied, then edited" — the rule
/// forward-only migrations rest on, enforced by the database rather
/// than by a lockfile in one repository (issues #28, #34).
///
/// The lockfile's hash covers the collected *file*; this covers the
/// embedded SQL. They answer different questions and are not compared.
#[must_use]
pub fn migration_checksum(sql: &str) -> String {
    use sha2::{Digest, Sha256};
    let digest = Sha256::digest(sql.as_bytes());
    let mut hex = String::with_capacity(64);
    for byte in digest {
        use std::fmt::Write as _;
        let _ = write!(hex, "{byte:02x}");
    }
    hex
}

/// The message a migration whose recorded checksum no longer matches
/// gets. Shared so both engines say the same thing.
#[must_use]
pub fn migration_edited(key: &str, recorded: &str, found: &str) -> String {
    format!(
        "migration `{key}` was already applied to this database with different SQL \
         (recorded sha256 {}…, embedded {}…). Applied migrations are never edited: \
         revert the change and write a new migration instead \
         (docs/MODULE-AUTHORING.md, step 3)",
        &recorded[..recorded.len().min(12)],
        &found[..found.len().min(12)]
    )
}

/// The module's migrations, per dialect. `postgres` differs from `sqlite`
/// only where the SQL truly differs (ADR 0004).
#[derive(Debug, Clone)]
pub struct Migrations {
    pub sqlite: &'static [SqlMigration],
    pub postgres: &'static [SqlMigration],
}

impl Migrations {
    pub const EMPTY: Migrations = Migrations {
        sqlite: &[],
        postgres: &[],
    };

    pub const fn sqlite(migrations: &'static [SqlMigration]) -> Self {
        Migrations {
            sqlite: migrations,
            postgres: &[],
        }
    }
}

impl Default for Migrations {
    fn default() -> Self {
        Self::EMPTY
    }
}

/// Everything a module's router needs: its declared ports, the typed
/// config, the bus, the templates and the venture identity.
pub struct ModuleContext {
    /// Only the ports the module declared in `requires()`/`optional()`.
    pub ports: Ports,
    /// Full config; module keys are prefixed (`EMAIL_SIGNUP_CONFIRM_TTL_DAYS`).
    pub config: Arc<dyn Config>,
    pub events: EventBus,
    pub templates: Arc<TemplateRegistry>,
    pub venture: Arc<Venture>,
    /// `true` when the venture mounted a UI renderer (ADR 0010). A module
    /// then defaults its landing redirects (confirmed, expired,
    /// unsubscribed, status) to `<api base>/ui/<module>/<action>/<page>`
    /// instead of pages the venture site has to provide.
    pub ui_mounted: bool,
}

/// A Factory Zero module. Object-safe; composed as `Arc<dyn Module>`.
///
/// Handlers get the request scope as an axum extractor:
/// `async fn join(scope: Scope, State(ctx): State<Arc<ModuleContext>>, ...)`.
/// There is no ambient "current request" (ADR 0007).
pub trait Module: Send + Sync + 'static {
    /// Kebab-case name; mounted at `/v1/<name>`.
    fn name(&self) -> &'static str;
    /// `env!("CARGO_PKG_VERSION")`, surfaced by `/__health`.
    fn version(&self) -> &'static str;
    /// Contract version, checked by `Harness::build`.
    fn harness_api(&self) -> u32 {
        HARNESS_API
    }
    /// Ports the module cannot run without; missing = build error.
    fn requires(&self) -> &'static [Port];
    /// Ports the module uses when present.
    fn optional(&self) -> &'static [Port] {
        &[]
    }
    /// Table names this module owns; duplicates across modules are a build
    /// error.
    fn tables(&self) -> &'static [&'static str] {
        &[]
    }
    /// Event names this module emits (`"<module>.<event>"`), listed by
    /// `/__health`.
    fn emits(&self) -> &'static [&'static str] {
        &[]
    }
    /// Whether the module has public write endpoints; drives the
    /// production-captcha rule (section 11).
    fn public_writes(&self) -> bool {
        false
    }
    /// The module's migrations, embedded per dialect.
    fn migrations(&self) -> Migrations;
    /// Rejects invalid configuration: missing required keys or malformed
    /// values, reported together with the module name.
    ///
    /// **When it runs.** The conformance kit calls it, and a module's own
    /// tests should. It cannot run at `Harness::build` or in `fz doctor`,
    /// because neither has the deploy config — the values live on the runtime
    /// `Env` and only exist per request. The Cloudflare runtime therefore runs
    /// it **once at cold start** and logs any failure loudly (`console_error!`,
    /// so it reaches Workers Logs); it does not fail the boot, so a
    /// misconfigured module still degrades per request (issue #101) rather
    /// than taking the whole Worker down. Turning that into a hard boot
    /// failure is a deployment decision for an ADR.
    ///
    /// # Errors
    ///
    /// `Err` listing every invalid or missing key for this module.
    fn validate_config(&self, cfg: &dyn Config) -> Result<(), ConfigError>;
    /// The module's router, nested under `/v1/<name>`.
    fn router(&self, ctx: ModuleContext) -> axum::Router;
    /// Routes this module serves at the root under `/.well-known`, for
    /// spec-mandated discovery documents (OIDC `openid-configuration`,
    /// `jwks.json`) that must live outside `/v1` (issue #46). Paths are
    /// relative to the prefix: register `/jwks.json`, not
    /// `/.well-known/jwks.json`.
    ///
    /// At most one module may provide one: discovery URLs are a singleton
    /// namespace, so `Harness::build` fails (naming every provider) when
    /// two modules return a router here. `None` by default.
    fn well_known(&self) -> Option<axum::Router> {
        None
    }
    /// The module's UI surface (ADR 0010): the actions a renderer may
    /// offer and the views that compose them. Input schemas come from
    /// the handler's own body types (`Action::input::<Body>()`), so the
    /// declaration cannot drift from the route. `Harness::build`
    /// validates it; `GET /__surface` serves the composition. Default:
    /// nothing, and a module that declares nothing renders nothing.
    fn surface(&self) -> Surface {
        Surface::none()
    }
    /// Handlers for events other modules emit; registered at
    /// `Harness::build`.
    fn events(&self) -> Vec<(EventName, EventHandler)> {
        Vec::new()
    }
    /// Scheduled work (`cron` is the trigger expression). Default: none.
    fn scheduled<'a>(
        &'a self,
        ctx: &'a ModuleContext,
        cron: &'a str,
    ) -> BoxFuture<'a, Result<(), AnyError>> {
        let _ = (ctx, cron);
        Box::pin(async { Ok(()) })
    }
}