boatramp-types 0.35.2

//! Compute workloads: legacy apps run as Firecracker microVMs.
//!
//! This is the wasm-clean **artifact model** — the content-addressed, immutable
//! [`ComputeSpec`] (rootfs/kernel/spec, exactly like a site deployment) and the
//! mutable [`ComputeWorkload`] desired state (active version + replicas +
//! placement). The executor that actually boots a microVM from a spec
//! (`boatramp-firecracker`, KVM-only) and the scheduler that places it are
//! native-only and live elsewhere; this module is just the shared types + their
//! content-addressing, so the CLI, control plane, and executor agree.

use std::collections::BTreeMap;

use serde::{Deserialize, Serialize};

use crate::manifest::sha256_hex;

/// KV key prefix for immutable, content-addressed compute specs. Stays **global**
/// (a content hash is a self-authenticating capability; specs dedup across projects).
pub const SPEC_PREFIX: &str = "computever/";

/// The mutable desired-state key for a workload, **project-scoped** (0.2.0):
/// `project/<proj>/compute/<name>`. `project` is a bare `&str` (this crate is
/// wasm-clean); `boatramp-core` callers pass `ProjectRef::as_str()`.
pub fn workload_key(project: &str, name: &str) -> String {
    format!("project/{project}/compute/{name}")
}

/// The prefix listing every workload's desired state in a project.
pub fn workloads_prefix(project: &str) -> String {
    format!("project/{project}/compute/")
}

/// The immutable spec key for a content hash (global CAS).
pub fn spec_key(hash: &str) -> String {
    format!("{SPEC_PREFIX}{hash}")
}

/// What to do when a workload's guest process exits.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum RestartPolicy {
    /// Never restart (run-to-completion / job).
    Never,
    /// Restart only on a non-zero exit.
    OnFailure,
    /// Always keep it running (the default for a service).
    #[default]
    Always,
}

/// The isolation a workload **requires** — the floor the operator's site policy
/// and the available backends are matched against.
/// This is the workload's stated need, distinct from the isolation *class* a
/// backend provides.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum IsolationRequirement {
    /// Shared-kernel isolation is acceptable (a namespace/container is fine).
    /// The default — strong isolation is opt-in.
    #[default]
    Trusted,
    /// Strong isolation is required: only a microVM (KVM) or a managed platform
    /// may run this workload, never a shared-kernel container.
    Untrusted,
}

impl IsolationRequirement {
    /// Whether this is the default (`Trusted`) — used to omit it from the
    /// serialized spec so existing specs keep their content hash.
    pub fn is_trusted(&self) -> bool {
        matches!(self, Self::Trusted)
    }
}

/// The source of a workload's **root filesystem**. Each variant is one concrete
/// artifact form, matched 1:1 to the backends that accept it — modelled explicitly
/// rather than overloading one string, because an image reference, a tar archive, and
/// a rootfs block image are genuinely different things and a mismatch should be a
/// typed error.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum RootSource {
    /// An **OCI image reference** (`repo:tag` or a digest) a runtime **pulls** from a
    /// registry; its unpacked layers become the root filesystem. Backends: `docker`,
    /// `cloudflare`. [`ComputeSpec::kernel`] does not apply.
    Image(String),
    /// A **tar rootfs archive** — a blob hash in the shared store — that the node
    /// **stages and unpacks** into a directory to run. Backend: the native `container`
    /// runtime. [`ComputeSpec::kernel`] does not apply.
    Tar(String),
    /// A **rootfs filesystem image** — a blob hash in the shared store — that the node
    /// **stages and attaches** as the guest's root **block device**. The filesystem is
    /// opaque to boatramp: the guest kernel mounts whatever it finds (`ext4` by
    /// default, since `compute build` uses `mke2fs`, but any kernel-supported
    /// filesystem works). Backend: the `firecracker` micro-VM, which pairs it with
    /// [`ComputeSpec::kernel`].
    Rootfs(String),
}

impl RootSource {
    /// The underlying reference string (an image reference for [`RootSource::Image`],
    /// a blob hash for [`RootSource::Tar`] / [`RootSource::Rootfs`]).
    pub fn as_str(&self) -> &str {
        match self {
            Self::Image(s) | Self::Tar(s) | Self::Rootfs(s) => s,
        }
    }
}

/// A persistent volume attached to the guest (a host block image, snapshotted
/// to blob storage for durability). Opt-in; the default rootfs is read-only with
/// an ephemeral scratch drive.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct VolumeRef {
    /// In-guest mount point.
    pub mount: String,
    /// Volume name (the host tracks its backing image).
    pub name: String,
    /// Size in MiB (used when first provisioning).
    pub size_mib: u32,
}

/// The generic default startup grace (seconds) for a compute workload — the window a
/// freshly launched replica has to become healthy before the reconcile loop treats a
/// still-unhealthy one as a broken launch. Generic compute + micro-VM workloads use
/// this; the managed-database synthesizer overrides it per engine (slower `initdb`).
pub fn default_startup_grace_secs() -> u32 {
    30
}

/// An immutable, content-addressed compute workload version (the analogue of a
/// deployment manifest). Stored at `computever/<hash>`; the rootfs + kernel are
/// blob hashes in the shared blob store (deduped, cached forever).
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct ComputeSpec {
    /// Pinned schema discriminant (`v1`).
    #[serde(default = "crate::schema_version")]
    pub version: u32,
    /// The source of the workload's root filesystem: an OCI image reference, a tar
    /// rootfs archive, or a rootfs filesystem image, per the target substrate (see
    /// [`RootSource`]).
    pub root: RootSource,
    /// Blob hash of the `vmlinux` kernel (shared across workloads). Applies only to
    /// the micro-VM substrate (a [`RootSource::Rootfs`] source); ignored otherwise, so
    /// an image/tar workload omits it (empty ⇒ absent from the wire + the content hash).
    #[serde(default, skip_serializing_if = "String::is_empty")]
    pub kernel: String,
    /// Kernel boot cmdline override; `None` uses the executor default.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub kernel_cmdline: Option<String>,
    /// Virtual CPUs.
    pub vcpus: u32,
    /// Guest memory in MiB.
    pub mem_mib: u32,
    /// The in-guest entrypoint (argv) the init execs.
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub entrypoint: Vec<String>,
    /// Environment variables for the entrypoint.
    #[serde(default, skip_serializing_if = "BTreeMap::is_empty")]
    pub env: BTreeMap<String, String>,
    /// The TCP port the app listens on inside the guest (the gateway targets it).
    pub port: u16,
    /// Restart policy for the guest process.
    #[serde(default)]
    pub restart: RestartPolicy,
    /// Seconds a freshly launched replica is given to become healthy before the
    /// reconcile loop treats a `Running`-but-unhealthy replica as a broken launch to
    /// stop + relaunch. Within this grace the replica is "starting" (left alone), so a
    /// slow-initializing image — a stock database's first `initdb` — is not killed
    /// mid-init into a crash loop. Generic default is 30s (see [`default_startup_grace_secs`]);
    /// the managed-database synthesizer raises it per engine. `#[serde(default …)]` keeps
    /// older stored specs (no field) deserializing with the default — schema stays v1.
    #[serde(default = "default_startup_grace_secs")]
    pub startup_grace_secs: u32,
    /// Snapshot + stop when idle; restore on the next request (cold start).
    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
    pub scale_to_zero: bool,
    /// Persistent volumes (opt-in).
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub volumes: Vec<VolumeRef>,
    /// Allow a writable root filesystem instead of the hardened read-only-root
    /// default. Opt-in and honored **only under the single-tenant isolation
    /// posture** (a backend forces read-only root under the multi-tenant guard).
    /// The idiomatic path for app writes remains a [`VolumeRef`]; this is for images
    /// that write outside a declared volume. Default off; omitted from the wire + the
    /// content hash when false (back-compat).
    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
    pub writable_root: bool,
    /// Linux capabilities to add back on top of the dropped-`ALL` default of the
    /// shared-kernel backends (docker / native container), so an image whose
    /// entrypoint needs a specific capability (e.g. a stock database that `chown`s its
    /// data dir and `gosu`-drops to its user) can init. Names are the short form
    /// without the `CAP_` prefix (`"CHOWN"`, `"SETUID"`, …). Honored **only under the
    /// single-tenant isolation posture** — the multi-tenant guard strips it, exactly
    /// like [`writable_root`](Self::writable_root). Empty ⇒ omitted from the wire + the
    /// content hash (back-compat).
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub cap_add: Vec<String>,
    /// Run the entrypoint as this user instead of the backend default. `"uid"` or
    /// `"uid:gid"` (numeric). On the shared-kernel backends this lets a stock image
    /// run rootless against a pre-owned volume — the entrypoint skips the `chown` +
    /// privilege-drop that would otherwise need capabilities, so it needs none. A
    /// hardening (not a relaxation), so it is honored under any posture. `None` ⇒ the
    /// backend default; omitted from the wire + the content hash (back-compat).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub user: Option<String>,
    /// Isolation the workload requires; selects which backends are eligible.
    /// Default `Trusted`; omitted from the serialized
    /// spec when default, so existing specs keep their content hash.
    #[serde(default, skip_serializing_if = "IsolationRequirement::is_trusted")]
    pub isolation: IsolationRequirement,
    /// Optional preferred backend id (`vmm`/`container`/`cloudflare`/`docker`);
    /// the scheduler honors it when the backend is eligible, else falls back.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub prefer_backend: Option<String>,
    /// Managed resources this workload depends on — the opaque-process analogue of a
    /// handler's `imports`. boatramp resolves each to a **tenant-scoped** endpoint +
    /// credential at launch and injects the address into the guest env, so a workload
    /// reaches the managed `sql` (and, later, kv/blob/messaging) without a hand-glued
    /// URL. Empty ⇒ omitted from the wire + the content hash (back-compat).
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub bindings: Vec<ComputeBinding>,
}

/// A managed-resource dependency a compute workload declares. It names a *resource*,
/// never a project: the owning project comes from the workload's key
/// (`project/<proj>/compute/<name>`), so a workload cannot request another tenant's
/// data. boatramp resolves it at launch and injects the endpoint into the guest env.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct ComputeBinding {
    /// Which managed resource kind.
    pub kind: BindingKind,
    /// The named database/store within the kind (`""` = the site default, matching
    /// `sql.open("")`).
    #[serde(default, skip_serializing_if = "String::is_empty")]
    pub name: String,
    /// The env var the resolved endpoint URL is injected as; `None` ⇒ the kind default
    /// (`sql` → `BOATRAMP_SQL_URL`). The credential is injected as `<url_env>_AUTH_TOKEN`.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub url_env: Option<String>,
}

/// The managed-resource kinds a [`ComputeBinding`] may name. Phase 0 implements `Sql`;
/// the others are reserved for the shared resolver mechanism.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum BindingKind {
    /// The managed `sql` database (per-site libsql, or a named external DB).
    Sql,
    /// Per-site key-value store (Phase 2).
    Kv,
    /// Per-site blob store (Phase 2).
    Blob,
    /// Per-site pub/sub + queues (Phase 2).
    Messaging,
}

impl ComputeBinding {
    /// The env var the endpoint URL is injected as (explicit `url_env`, else the kind
    /// default). The auth token is injected as this name plus `_AUTH_TOKEN`.
    pub fn url_env(&self) -> String {
        self.url_env
            .clone()
            .unwrap_or_else(|| self.kind.default_url_env().to_string())
    }
}

impl BindingKind {
    /// A **stable** 1-byte discriminant for this kind, used where a derivation must not shift if the
    /// enum is ever reordered or a variant renamed — the compute shims' token HMAC, where
    /// `format!("{:?}", kind)` would silently rotate every live token on a rename. Append-only:
    /// NEVER renumber an existing variant.
    pub fn stable_tag(self) -> u8 {
        match self {
            Self::Sql => 1,
            Self::Kv => 2,
            Self::Blob => 3,
            Self::Messaging => 4,
        }
    }

    /// The default env var an endpoint of this kind is injected as.
    pub fn default_url_env(self) -> &'static str {
        match self {
            Self::Sql => "BOATRAMP_SQL_URL",
            Self::Kv => "BOATRAMP_KV_URL",
            Self::Blob => "BOATRAMP_BLOB_URL",
            Self::Messaging => "BOATRAMP_MESSAGING_URL",
        }
    }
}

impl ComputeSpec {
    /// The content hash of this spec — its `computever/<hash>` id. Computed over
    /// the canonical JSON so identical specs dedupe (like a deployment id).
    pub fn id(&self) -> String {
        let canonical = serde_json::to_vec(self).expect("ComputeSpec serializes");
        sha256_hex(&canonical)
    }
}

/// Placement constraints: where a workload's replicas may run.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct PlacementConstraints {
    /// If non-empty, only nodes in one of these regions are eligible.
    pub regions: Vec<String>,
    /// Required node labels (all must match a node's advertised labels).
    pub labels: BTreeMap<String, String>,
}

impl PlacementConstraints {
    /// Whether a node with `node_region` + `node_labels` satisfies these
    /// constraints.
    pub fn allows(
        &self,
        node_region: Option<&str>,
        node_labels: &BTreeMap<String, String>,
    ) -> bool {
        if !self.regions.is_empty() {
            match node_region {
                Some(r) if self.regions.iter().any(|want| want == r) => {}
                _ => return false,
            }
        }
        self.labels
            .iter()
            .all(|(k, v)| node_labels.get(k).is_some_and(|nv| nv == v))
    }
}

/// The mutable desired state for a workload (`compute/<name>`): the active spec
/// version, replica count, and placement. Activation is a pointer flip to a new
/// spec hash — the same atomic, roll-back-able model as a site deployment.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct ComputeWorkload {
    /// Pinned schema discriminant (`v1`).
    #[serde(default = "crate::schema_version")]
    pub version: u32,
    /// Human label (the workload name is the KV key).
    pub name: String,
    /// The active [`ComputeSpec`] content hash (`computever/<hash>`).
    pub active: String,
    /// Desired replica count.
    pub replicas: u32,
    /// Placement constraints.
    #[serde(default)]
    pub placement: PlacementConstraints,
}

/// The default replica count for a workload (1) — a service runs one replica
/// unless the manifest / request asks for more.
pub fn default_replicas() -> u32 {
    1
}

/// The body of `PUT /api/compute/:name` — an immutable [`ComputeSpec`] plus the
/// desired replica count and [`PlacementConstraints`]. This is the SINGLE typed
/// schema for a compute workload's desired state: both the server handler
/// (`put_compute`) and the client manifest ([`crate::…::ApplyCompute`] mirrors
/// these fields) deserialize into it, so there is no schema duplication and the
/// client can fail fast on a malformed spec BEFORE the request leaves the host.
/// The server still runs its own semantic validation (kernel defaulting, name
/// screening) on top — the typed client parse is an additive gate, not a
/// replacement.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct PutComputeRequest {
    /// The immutable workload spec (rootfs/kernel blob hashes + sizing).
    pub spec: ComputeSpec,
    /// Desired replica count (default 1).
    #[serde(default = "default_replicas")]
    pub replicas: u32,
    /// Placement constraints.
    #[serde(default)]
    pub placement: PlacementConstraints,
}

// ---------------------------------------------------------------------------
// Declarative managed-database surface (v0.6.0, #501 Stage B).
// ---------------------------------------------------------------------------

/// The engine a declared managed database runs — the SAFE, typed subset of the
/// node-static `ExternalDatabaseConfig.kind` string. A manifest may only declare an
/// engine boatramp fully manages (provisions + seals the credential for): Postgres
/// or MySQL. `libsql` is deliberately absent — the embedded engine is the per-site
/// default and needs no declaration, and its `path` source is host-fs (excluded).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum ApplyDatabaseKind {
    /// PostgreSQL (lowered to `ExternalDatabaseConfig.kind = "postgres"`).
    Postgres,
    /// MySQL (lowered to `ExternalDatabaseConfig.kind = "mysql"`).
    Mysql,
}

impl ApplyDatabaseKind {
    /// The node-static `ExternalDatabaseConfig.kind` string this lowers to.
    pub fn as_config_kind(self) -> &'static str {
        match self {
            Self::Postgres => "postgres",
            Self::Mysql => "mysql",
        }
    }
}

/// How a declared managed database is physically isolated per tenant — the typed
/// projection of `ExternalDatabaseConfig.tenant` (`TenantIsolation`). `Single` = a
/// dedicated server (container) per tenant; `Shared` = one server hosting a
/// per-tenant database + login role (grant-isolated).
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum ApplyDatabaseTenant {
    /// A dedicated database server (its own container) per tenant. The default.
    #[default]
    Single,
    /// One shared server hosting a per-tenant database + role (grant-isolated).
    Shared,
}

/// The grain of a tenant for a declared managed database — the typed projection of
/// `ExternalDatabaseConfig.tenant_scope` (`TenantScope`). `Project` (default) or
/// `Site`.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum ApplyDatabaseScope {
    /// A tenant is a **project** (the default).
    #[default]
    Project,
    /// A tenant is a **site** (finer than project).
    Site,
}

/// A coarse sizing **preset** for a declared managed database — NOT raw VM knobs.
/// The manifest author picks a t-shirt size; boatramp maps it to concrete
/// vcpus/mem/volume at lowering time (see [`ApplyDatabaseSize::resources`]), so the
/// declarative surface never exposes an unbounded resource request (the errno-28
/// disk-full / DoS guard). Default `Small`.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum ApplyDatabaseSize {
    /// 1 vCPU / 512 MiB / 10 GiB volume — the default, matching the stock
    /// `managed_db_spec` sizing.
    #[default]
    Small,
    /// 2 vCPU / 2 GiB / 50 GiB volume.
    Medium,
    /// 4 vCPU / 8 GiB / 200 GiB volume.
    Large,
}

impl ApplyDatabaseSize {
    /// The `(vcpus, mem_mib, volume_size_mib)` this preset maps to. The single
    /// authority for the preset → resources mapping, so the CLI (rendering) and the
    /// server (lowering) agree. Deliberately bounded: `Large` is the ceiling a
    /// manifest can request — there is no raw-knob escape hatch.
    pub fn resources(self) -> (u32, u32, u32) {
        match self {
            // (vcpus, mem_mib, volume_size_mib)
            Self::Small => (1, 512, 10 * 1024),
            Self::Medium => (2, 2 * 1024, 50 * 1024),
            Self::Large => (4, 8 * 1024, 200 * 1024),
        }
    }
}

/// The operator ceilings a declared database's optional tuning knobs are CAPPED to
/// (a DoS / resource guard — the manifest author can lower a knob, never raise it
/// past the ceiling). Applied at lowering time in `boatramp-node`; centralized here
/// so the cap is one authority.
pub mod apply_db_caps {
    /// Maximum `pool_max` a manifest may request (connections). A too-large pool
    /// exhausts the server's connection slots.
    pub const MAX_POOL: u32 = 64;
    /// Maximum `connect_timeout_secs` a manifest may request.
    pub const MAX_CONNECT_TIMEOUT_SECS: u64 = 60;
    /// Maximum `startup_grace_secs` a manifest may request (bounds how long a
    /// never-healthy replica is left running before the reconcile relaunches it).
    pub const MAX_STARTUP_GRACE_SECS: u32 = 600;

    /// Default operator ceiling on the **number** of declared databases a single
    /// project may hold (#501 Stage B MEDIUM-1 — the disk-exhaustion / errno-28 guard).
    /// Each declared DB eagerly provisions a 10–200 GiB volume, so without a per-project
    /// cap a `Project·Admin` could declare an unbounded number and exhaust the node's
    /// disk. Operator-overridable via `handlers.bindings.sql.max_declared_databases`;
    /// enforced fail-closed at `declare`.
    pub const DEFAULT_MAX_DECLARED_DATABASES_PER_PROJECT: usize = 16;

    /// Default operator ceiling on the **aggregate provisioned volume** (MiB) across all
    /// of a project's declared databases (#501 Stage B MEDIUM-1). 512 GiB — comfortably
    /// above the 16-DB count cap at the Small preset (16 × 10 GiB = 160 GiB) yet a hard
    /// backstop against a handful of Large (200 GiB) declarations. Operator-overridable
    /// via `handlers.bindings.sql.max_declared_volume_mib`; enforced fail-closed at
    /// `declare` by summing the existing declarations' volumes + the incoming one.
    pub const DEFAULT_MAX_DECLARED_VOLUME_MIB: u64 = 512 * 1024;
}

/// A **declared managed database** in an [`ApplyManifest`](crate) `databases:` block
/// (v0.6.0, #501 Stage B). This is a TYPED PROJECTION of the node-static
/// `ExternalDatabaseConfig` restricted to the fields that are SAFE for a project
/// author to declare — the security contract.
///
/// # The security contract (what is DELIBERATELY absent)
///
/// A declared database is DEFINITIONALLY the "boatramp fully manages + seals the
/// credential" path: it carries **no** secret / env-var / URL / host-fs / image
/// field, so a manifest can neither reference a secret nor pick an arbitrary OCI
/// image. The EXCLUDED fields (NOT part of this struct — that exclusion IS the
/// contract):
///
/// - `image` — arbitrary-OCI RCE (no allowlist); boatramp always picks the stock
///   engine image at lowering.
/// - `password_env` — omitting it is what selects the managed-credential path
///   (`ExternalDatabaseConfig::is_managed_credential`); a declared DB can NEVER bring
///   its own password.
/// - `url_env` / `read_url_env` / `migration_url_env` — BYO-secret / SSRF /
///   arbitrary-host reach.
/// - `path` — host-fs traversal.
/// - `compute` — the manifest does NOT let the author name an arbitrary compute
///   workload; boatramp DERIVES the per-project managed DB server workload name at
///   lowering, so a manifest can only ever provision onto its own project's server.
///
/// The struct uses `deny_unknown_fields` so a manifest that tries to smuggle one of
/// the excluded keys fails to parse rather than being silently ignored.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct ApplyDatabase {
    /// The binding name — how a guest reaches it via `sql.open("<name>")` and the
    /// `{name}` path segment of the `project/{project}/database/{name}` store key.
    pub name: String,
    /// The engine (Postgres or MySQL). Lowered to `ExternalDatabaseConfig.kind`.
    pub kind: ApplyDatabaseKind,
    /// The engine major version (e.g. `16` for Postgres). Advisory metadata carried
    /// on the stored binding; a version CHANGE on re-apply routes through the
    /// owner-gated migrate/repair path (never a silent re-init). `None` ⇒ the engine
    /// default.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub version: Option<u32>,
    /// Trusted extensions to make available (Postgres). Advisory metadata; enabling
    /// one still routes through the owner-gated migration `Extension` step +
    /// operator allowlist — this does NOT bypass that gate.
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub extensions: Vec<String>,
    /// Coarse sizing preset (`small`/`medium`/`large`). Maps to bounded
    /// vcpus/mem/volume at lowering — NOT raw VM knobs.
    #[serde(default)]
    pub size: ApplyDatabaseSize,
    /// Isolation mechanism (`single` = dedicated container per tenant; `shared` =
    /// one server, per-tenant db + role). Lowered to `ExternalDatabaseConfig.tenant`.
    /// A CHANGE on re-apply is REFUSED (silent data-loss/orphan guard).
    #[serde(default)]
    pub tenant: ApplyDatabaseTenant,
    /// Tenant grain (`project`/`site`). Lowered to
    /// `ExternalDatabaseConfig.tenant_scope`. A CHANGE on re-apply is REFUSED.
    #[serde(default)]
    pub tenant_scope: ApplyDatabaseScope,
    /// Open every transaction `READ ONLY`.
    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
    pub read_only: bool,
    /// Opt-in native-RLS session injection (`rls_session`). See
    /// `ExternalDatabaseConfig.rls_session`.
    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
    pub rls_session: bool,
    /// The Postgres session GUC for the host-resolved tenant (RLS backstop). Only
    /// honored with `rls_session` on + Postgres.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub tenant_guc: Option<String>,
    /// The session GUC for the anonymous session axis (RLS backstop).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub session_guc: Option<String>,
    /// The reserved sentinel written to `tenant_guc` on an `all`-scoped read.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub tenant_all_marker: Option<String>,
    /// Maximum pooled connections. CAPPED to [`apply_db_caps::MAX_POOL`] at lowering.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub pool_max: Option<u32>,
    /// Connection/acquire timeout in seconds. CAPPED to
    /// [`apply_db_caps::MAX_CONNECT_TIMEOUT_SECS`] at lowering.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub connect_timeout_secs: Option<u64>,
    /// Startup grace in seconds for the managed server's first `initdb`. CAPPED to
    /// [`apply_db_caps::MAX_STARTUP_GRACE_SECS`] at lowering.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub startup_grace_secs: Option<u32>,
}

impl ApplyDatabase {
    /// The identity fields a re-apply may NEVER change (silent data-loss / orphan
    /// guard): `kind`, `tenant`, `tenant_scope`. (There is no author-supplied
    /// `compute` to compare — boatramp derives it, so it cannot drift.) Returns the
    /// first differing field name, or `None` if the two declarations agree on all
    /// identity fields. `version`/`extensions`/`size`/rls-knobs are intentionally NOT
    /// compared — those route through migrate/repair or are documented re-tuning.
    pub fn identity_change(&self, prior: &Self) -> Option<&'static str> {
        if self.kind != prior.kind {
            return Some("kind");
        }
        if self.tenant != prior.tenant {
            return Some("tenant");
        }
        if self.tenant_scope != prior.tenant_scope {
            return Some("tenant_scope");
        }
        None
    }
}

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

    fn spec() -> ComputeSpec {
        ComputeSpec {
            version: crate::SCHEMA_VERSION,
            root: RootSource::Rootfs("a".repeat(64)),
            kernel: "b".repeat(64),
            kernel_cmdline: None,
            vcpus: 2,
            mem_mib: 512,
            entrypoint: vec!["/app".into(), "--serve".into()],
            env: BTreeMap::from([("PORT".to_string(), "8080".to_string())]),
            port: 8080,
            restart: RestartPolicy::Always,
            startup_grace_secs: 30,
            scale_to_zero: true,
            volumes: vec![],
            writable_root: false,
            cap_add: Vec::new(),
            user: None,
            isolation: IsolationRequirement::Trusted,
            prefer_backend: None,
            bindings: vec![],
        }
    }

    #[test]
    fn empty_bindings_do_not_change_the_spec_hash() {
        // A spec that declares no bindings serializes without the field, so it hashes
        // identically to a pre-bindings spec (back-compat).
        let a = spec();
        let json = serde_json::to_string(&a).unwrap();
        assert!(!json.contains("bindings"), "empty bindings are omitted");

        // Declaring a binding is recorded and changes the content hash.
        let mut b = spec();
        b.bindings = vec![ComputeBinding {
            kind: BindingKind::Sql,
            name: String::new(),
            url_env: None,
        }];
        assert_ne!(a.id(), b.id(), "a declared binding changes the id");
        assert!(serde_json::to_string(&b).unwrap().contains("bindings"));
    }

    #[test]
    fn binding_kind_parses_lowercase_and_url_env_defaults_per_kind() {
        assert_eq!(
            serde_json::from_str::<BindingKind>("\"sql\"").unwrap(),
            BindingKind::Sql
        );
        let sql = ComputeBinding {
            kind: BindingKind::Sql,
            name: String::new(),
            url_env: None,
        };
        assert_eq!(sql.url_env(), "BOATRAMP_SQL_URL");
        let custom = ComputeBinding {
            kind: BindingKind::Sql,
            name: "analytics".into(),
            url_env: Some("ANALYTICS_URL".into()),
        };
        assert_eq!(custom.url_env(), "ANALYTICS_URL");
    }

    #[test]
    fn spec_id_is_stable_and_content_addressed() {
        let a = spec();
        let mut b = spec();
        assert_eq!(a.id(), b.id(), "identical specs share an id");
        b.vcpus = 4;
        assert_ne!(a.id(), b.id(), "a changed field changes the id");
        assert_eq!(a.id().len(), 64);
    }

    #[test]
    fn default_isolation_does_not_change_the_spec_hash() {
        // `Trusted` (default) is omitted from the JSON, so a spec that doesn't
        // touch isolation hashes identically to one explicitly set to Trusted.
        let mut a = spec();
        a.isolation = IsolationRequirement::Trusted;
        let json = serde_json::to_string(&a).unwrap();
        assert!(!json.contains("isolation"), "default isolation is omitted");
        // Untrusted is recorded and changes the hash.
        let mut b = spec();
        b.isolation = IsolationRequirement::Untrusted;
        assert_ne!(a.id(), b.id());
        assert!(serde_json::to_string(&b).unwrap().contains("untrusted"));
    }

    #[test]
    fn spec_round_trips_through_json() {
        let a = spec();
        let json = serde_json::to_string(&a).unwrap();
        assert_eq!(serde_json::from_str::<ComputeSpec>(&json).unwrap(), a);
    }

    #[test]
    fn old_spec_without_startup_grace_deserializes_with_the_default() {
        // An additive, `#[serde(default)]` field keeps schema at v1: a spec stored
        // before `startup_grace_secs` existed (no such key) still deserializes, taking
        // the generic default (30). `deny_unknown_fields` is on, so this proves the
        // field is genuinely optional on read.
        let old = r#"{
            "version": 1,
            "root": { "rootfs": "aaaa" },
            "vcpus": 1,
            "mem_mib": 256,
            "port": 8080
        }"#;
        let spec: ComputeSpec = serde_json::from_str(old).expect("old spec deserializes");
        assert_eq!(spec.version, 1, "schema stays v1");
        assert_eq!(spec.startup_grace_secs, default_startup_grace_secs());
        assert_eq!(spec.startup_grace_secs, 30);
    }

    #[test]
    fn keyspace_helpers() {
        assert_eq!(
            workload_key("default", "api"),
            "project/default/compute/api"
        );
        assert_eq!(workload_key("acme", "api"), "project/acme/compute/api");
        assert_eq!(workloads_prefix("default"), "project/default/compute/");
        // The spec body is content-addressed and stays global (dedup across projects).
        assert_eq!(spec_key("deadbeef"), "computever/deadbeef");
    }

    #[test]
    fn placement_matches_region_and_labels() {
        let c = PlacementConstraints {
            regions: vec!["eu".into()],
            labels: BTreeMap::from([("gpu".to_string(), "yes".to_string())]),
        };
        let labels = BTreeMap::from([("gpu".to_string(), "yes".to_string())]);
        assert!(c.allows(Some("eu"), &labels));
        assert!(!c.allows(Some("us"), &labels), "wrong region");
        assert!(!c.allows(Some("eu"), &BTreeMap::new()), "missing label");
        // No constraints → any node.
        assert!(PlacementConstraints::default().allows(None, &BTreeMap::new()));
    }
}