lightshuttle-export 0.4.0

//! Helm emitter: renders an [`ExportModel`] into a chart with a
//! `Chart.yaml`, a `values.yaml` and one template per resource.
//!
//! Two engines live here. `Chart.yaml` and `values.yaml` are real data,
//! so they are typed structs serialised with `serde_norway`. The
//! `templates/*.yaml` files are Go templates: their `{{ ... }}`
//! directives are literals, written as text, while the structural parts
//! (ports, probes, volumes) are derived from the resolved spec.

use std::collections::BTreeMap;
use std::fmt::Write as _;
use std::time::Duration;

use lightshuttle_manifest::ImagePullPolicy;
use lightshuttle_spec::{ContainerSpec, HealthcheckSpec, ImageSource, VolumeSource};
use serde::Serialize;

use crate::emit::Emitter;
use crate::error::Result;
use crate::model::{ExportModel, ExportProject, Target};
use crate::resolve::{
    SECRET_MARKERS, chart_name_for, chart_version_for, dns_name, enabled_for,
    image_pull_policy_for, namespace_for, replicas_for,
};

/// Emits a Helm chart from the export model.
pub struct HelmEmitter;

impl Emitter for HelmEmitter {
    fn target(&self) -> Target {
        Target::Helm
    }

    fn emit(&self, model: &ExportModel) -> Result<crate::ExportArtifacts> {
        let export = model.export.as_ref();
        let mut artifacts = crate::ExportArtifacts::new();

        artifacts.push("Chart.yaml", chart_yaml(&model.project, export)?);
        artifacts.push("values.yaml", values_yaml(model)?);

        for service in &model.services {
            if !enabled_for(Target::Helm, &service.spec.resource, export) {
                continue;
            }
            let name = dns_name(&service.spec.resource);
            artifacts.push(
                format!("templates/{name}.yaml"),
                resource_template(&service.spec, &name),
            );
        }

        Ok(artifacts)
    }
}

fn chart_yaml(
    project: &ExportProject,
    export: Option<&lightshuttle_manifest::ExportConfig>,
) -> Result<String> {
    let chart = Chart {
        api_version: "v2",
        name: dns_name(&chart_name_for(&project.name, export)),
        version: chart_version_for(project.version.as_deref(), export),
        description: format!("Helm chart for {} generated by LightShuttle", project.name),
    };
    to_yaml(&chart)
}

fn values_yaml(model: &ExportModel) -> Result<String> {
    let export = model.export.as_ref();
    let namespace = namespace_for(&model.project.name, export);

    let mut services: BTreeMap<String, ServiceValues> = BTreeMap::new();
    for service in &model.services {
        if !enabled_for(Target::Helm, &service.spec.resource, export) {
            continue;
        }
        let name = dns_name(&service.spec.resource);
        let (env, secrets) = split_env(&service.spec.env);
        let (repository, tag) = split_image(&service.spec.image);
        services.insert(
            name,
            ServiceValues {
                replicas: replicas_for(Target::Helm, &service.spec.resource, export),
                image: ImageValues {
                    repository,
                    tag,
                    pull_policy: pull_policy_str(image_pull_policy_for(
                        &service.spec.resource,
                        export,
                    ))
                    .to_owned(),
                },
                env,
                secrets,
            },
        );
    }

    to_yaml(&Values {
        namespace,
        services,
    })
}

/// Build the multi-document template for one resource.
fn resource_template(spec: &ContainerSpec, name: &str) -> String {
    let mut out = String::new();
    let _ = writeln!(out, "{{{{- $svc := index .Values.services {name:?} -}}}}");
    out.push_str(&deployment_block(spec, name));
    if !spec.ports.is_empty() {
        out.push_str("---\n");
        out.push_str(&service_block(spec, name));
    }
    if !split_env(&spec.env).0.is_empty() {
        out.push_str("---\n");
        out.push_str(&configmap_block(name));
    }
    if !split_env(&spec.env).1.is_empty() {
        out.push_str("---\n");
        out.push_str(&secret_block(name));
    }
    for volume in &spec.volumes {
        if let VolumeSource::Named(vol) = &volume.source {
            out.push_str("---\n");
            out.push_str(&pvc_block(name, &dns_name(vol)));
        }
    }
    out
}

fn deployment_block(spec: &ContainerSpec, name: &str) -> String {
    let mut s = String::new();
    let (has_config, has_secret) = {
        let (config_env, secret_env) = split_env(&spec.env);
        (!config_env.is_empty(), !secret_env.is_empty())
    };

    let _ = write!(
        s,
        "apiVersion: apps/v1\n\
         kind: Deployment\n\
         metadata:\n\
         \x20 name: {name}\n\
         \x20 namespace: {{{{ .Values.namespace }}}}\n\
         \x20 labels:\n\
         \x20\x20\x20 app: {name}\n\
         spec:\n\
         \x20 replicas: {{{{ $svc.replicas }}}}\n\
         \x20 selector:\n\
         \x20\x20\x20 matchLabels:\n\
         \x20\x20\x20\x20\x20 app: {name}\n\
         \x20 template:\n\
         \x20\x20\x20 metadata:\n\
         \x20\x20\x20\x20\x20 labels:\n\
         \x20\x20\x20\x20\x20\x20\x20 app: {name}\n\
         \x20\x20\x20 spec:\n\
         \x20\x20\x20\x20\x20 containers:\n\
         \x20\x20\x20\x20\x20 - name: {name}\n\
         \x20\x20\x20\x20\x20\x20\x20 image: \"{{{{ $svc.image.repository }}}}:{{{{ $svc.image.tag }}}}\"\n\
         \x20\x20\x20\x20\x20\x20\x20 imagePullPolicy: {{{{ $svc.image.pullPolicy }}}}\n"
    );

    if !spec.ports.is_empty() {
        s.push_str("        ports:\n");
        for port in &spec.ports {
            let _ = writeln!(s, "        - containerPort: {}", port.container_port);
        }
    }
    if has_config || has_secret {
        s.push_str("        envFrom:\n");
        if has_config {
            let _ = writeln!(
                s,
                "        - configMapRef:\n            name: {name}-config"
            );
        }
        if has_secret {
            let _ = writeln!(s, "        - secretRef:\n            name: {name}-secret");
        }
    }
    let mounts: Vec<(String, &str)> = named_mounts(spec);
    if !mounts.is_empty() {
        s.push_str("        volumeMounts:\n");
        for (vol, target) in &mounts {
            let _ = writeln!(s, "        - name: {vol}\n          mountPath: {target}");
        }
    }
    if let Some(dir) = &spec.working_dir {
        let _ = writeln!(s, "        workingDir: {dir}");
    }
    if let Some(hc) = &spec.healthcheck {
        let probe = probe_block(hc);
        let _ = write!(s, "        readinessProbe:\n{probe}");
        let _ = write!(s, "        livenessProbe:\n{probe}");
    }
    if !mounts.is_empty() {
        s.push_str("      volumes:\n");
        for (vol, _) in &mounts {
            let _ = writeln!(
                s,
                "      - name: {vol}\n        persistentVolumeClaim:\n          claimName: {name}-{vol}"
            );
        }
    }
    s
}

fn service_block(spec: &ContainerSpec, name: &str) -> String {
    let mut s = String::new();
    let _ = write!(
        s,
        "apiVersion: v1\n\
         kind: Service\n\
         metadata:\n\
         \x20 name: {name}\n\
         \x20 namespace: {{{{ .Values.namespace }}}}\n\
         \x20 labels:\n\
         \x20\x20\x20 app: {name}\n\
         spec:\n\
         \x20 selector:\n\
         \x20\x20\x20 app: {name}\n\
         \x20 ports:\n"
    );
    for port in &spec.ports {
        let _ = writeln!(
            s,
            "  - port: {p}\n    targetPort: {p}",
            p = port.container_port
        );
    }
    if spec.ports.is_empty() {
        s.push_str("  []\n");
    }
    s
}

fn configmap_block(name: &str) -> String {
    format!(
        "apiVersion: v1\n\
         kind: ConfigMap\n\
         metadata:\n\
         \x20 name: {name}-config\n\
         \x20 namespace: {{{{ .Values.namespace }}}}\n\
         \x20 labels:\n\
         \x20\x20\x20 app: {name}\n\
         data:\n\
         {{{{- range $k, $v := $svc.env }}}}\n\
         \x20 {{{{ $k }}}}: {{{{ $v | quote }}}}\n\
         {{{{- end }}}}\n"
    )
}

fn secret_block(name: &str) -> String {
    format!(
        "apiVersion: v1\n\
         kind: Secret\n\
         metadata:\n\
         \x20 name: {name}-secret\n\
         \x20 namespace: {{{{ .Values.namespace }}}}\n\
         \x20 labels:\n\
         \x20\x20\x20 app: {name}\n\
         stringData:\n\
         {{{{- range $k, $v := $svc.secrets }}}}\n\
         \x20 {{{{ $k }}}}: {{{{ $v | quote }}}}\n\
         {{{{- end }}}}\n"
    )
}

fn pvc_block(name: &str, volume: &str) -> String {
    format!(
        "apiVersion: v1\n\
         kind: PersistentVolumeClaim\n\
         metadata:\n\
         \x20 name: {name}-{volume}\n\
         \x20 namespace: {{{{ .Values.namespace }}}}\n\
         \x20 labels:\n\
         \x20\x20\x20 app: {name}\n\
         spec:\n\
         \x20 accessModes:\n\
         \x20 - ReadWriteOnce\n\
         \x20 resources:\n\
         \x20\x20\x20 requests:\n\
         \x20\x20\x20\x20\x20 storage: 1Gi\n"
    )
}

fn probe_block(hc: &HealthcheckSpec) -> String {
    let command = match hc.test.first().map(String::as_str) {
        Some("CMD") => hc.test[1..].to_vec(),
        Some("CMD-SHELL") if hc.test.len() > 1 => {
            vec!["sh".to_owned(), "-c".to_owned(), hc.test[1..].join(" ")]
        }
        _ => hc.test.clone(),
    };
    let mut s = String::from("          exec:\n            command:\n");
    for arg in &command {
        let _ = writeln!(s, "            - {arg}");
    }
    let _ = writeln!(s, "          periodSeconds: {}", secs(hc.interval));
    let _ = writeln!(s, "          timeoutSeconds: {}", secs(hc.timeout));
    let _ = writeln!(s, "          failureThreshold: {}", hc.retries);
    let _ = writeln!(
        s,
        "          initialDelaySeconds: {}",
        secs(hc.start_period)
    );
    s
}

/// Named volume mounts as `(volume_name, mount_path)`.
fn named_mounts(spec: &ContainerSpec) -> Vec<(String, &str)> {
    spec.volumes
        .iter()
        .filter_map(|v| match &v.source {
            VolumeSource::Named(name) => Some((dns_name(name), v.target.as_str())),
            _ => None,
        })
        .collect()
}

/// Secret values are replaced with a placeholder so the exported
/// chart never contains real credentials.
fn split_env(
    env: &std::collections::HashMap<String, String>,
) -> (BTreeMap<String, String>, BTreeMap<String, String>) {
    let mut config = BTreeMap::new();
    let mut secret = BTreeMap::new();
    for (key, value) in env {
        if SECRET_MARKERS
            .iter()
            .any(|m| key.to_ascii_uppercase().contains(m))
        {
            secret.insert(key.clone(), "***".to_owned());
        } else {
            config.insert(key.clone(), value.clone());
        }
    }
    (config, secret)
}

/// Split an image reference into `(repository, tag)` on the last colon.
fn split_image(image: &ImageSource) -> (String, String) {
    let reference = match image {
        ImageSource::Pull(img) => img.clone(),
        ImageSource::Build { tag, .. } => tag.clone(),
    };
    match reference.rsplit_once(':') {
        Some((repo, tag)) if !repo.is_empty() => (repo.to_owned(), tag.to_owned()),
        _ => (reference, "latest".to_owned()),
    }
}

fn pull_policy_str(policy: ImagePullPolicy) -> &'static str {
    match policy {
        ImagePullPolicy::Always => "Always",
        ImagePullPolicy::IfNotPresent => "IfNotPresent",
        ImagePullPolicy::Never => "Never",
    }
}

#[allow(clippy::cast_possible_truncation)]
fn secs(d: Duration) -> u32 {
    d.as_secs().min(u64::from(u32::MAX)) as u32
}

fn to_yaml<T: Serialize>(value: &T) -> Result<String> {
    serde_norway::to_string(value).map_err(|e| crate::ExportError::Unsupported {
        resource: "<helm>".to_owned(),
        target: "helm",
        reason: format!("failed to serialise chart data: {e}"),
    })
}

// --- Typed chart data ---------------------------------------------------

#[derive(Serialize)]
struct Chart {
    #[serde(rename = "apiVersion")]
    api_version: &'static str,
    name: String,
    version: String,
    description: String,
}

#[derive(Serialize)]
struct Values {
    namespace: String,
    services: BTreeMap<String, ServiceValues>,
}

#[derive(Serialize)]
struct ServiceValues {
    replicas: u32,
    image: ImageValues,
    #[serde(skip_serializing_if = "BTreeMap::is_empty")]
    env: BTreeMap<String, String>,
    #[serde(skip_serializing_if = "BTreeMap::is_empty")]
    secrets: BTreeMap<String, String>,
}

#[derive(Serialize)]
struct ImageValues {
    repository: String,
    tag: String,
    #[serde(rename = "pullPolicy")]
    pull_policy: String,
}