use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use thiserror::Error;

#[derive(Debug, Error)]
pub enum ManifestError {
    #[error("Invalid manifest: {0}")]
    Invalid(String),
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),
    #[error("YAML parse error: {0}")]
    Yaml(#[from] serde_yaml::Error),
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AppManifest {
    pub app: AppDefinition,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AppDefinition {
    pub id: String,
    pub name: String,
    pub version: String,
    pub description: Option<String>,

    #[serde(default)]
    pub container: ContainerConfig,

    #[serde(default)]
    pub dependencies: Vec<Dependency>,

    #[serde(default)]
    pub resources: ResourceLimits,

    #[serde(default)]
    pub security: SecurityPolicy,

    #[serde(default)]
    pub ports: Vec<PortMapping>,

    #[serde(default)]
    pub volumes: Vec<Volume>,

    #[serde(default)]
    pub environment: Vec<String>,

    #[serde(default)]
    pub health_check: Option<HealthCheck>,

    #[serde(default)]
    pub devices: Vec<String>,

    #[serde(flatten)]
    pub extensions: HashMap<String, serde_yaml::Value>,
}

#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct ContainerConfig {
    /// Pull source. Mutually exclusive with `build`. Exactly one of the two must be present.
    #[serde(default)]
    pub image: Option<String>,
    #[serde(default)]
    pub image_signature: Option<String>,
    #[serde(default = "default_pull_policy")]
    pub pull_policy: String,
    /// Local build source. Mutually exclusive with `image`.
    #[serde(default)]
    pub build: Option<BuildConfig>,
}

fn default_pull_policy() -> String {
    "if-not-present".to_string()
}

/// Build a container image locally from a Dockerfile rather than pulling from a registry.
///
/// When present on `ContainerConfig`, the orchestrator runs `podman build -t <tag> -f <dockerfile> <context>`
/// before starting the container. The resulting local image is referenced by `tag`.
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct BuildConfig {
    /// Build context directory (absolute path or relative to the manifest location).
    pub context: String,
    /// Dockerfile path relative to `context`. Defaults to `Dockerfile`.
    #[serde(default = "default_dockerfile")]
    pub dockerfile: String,
    /// Tag applied to the built image. Used as the container's image reference.
    pub tag: String,
    /// Optional `--build-arg KEY=VALUE` pairs passed to the build.
    #[serde(default)]
    pub build_args: HashMap<String, String>,
}

fn default_dockerfile() -> String {
    "Dockerfile".to_string()
}

/// Resolved pull-or-build decision after manifest validation.
///
/// `ContainerConfig::resolve()` produces this. The orchestrator matches on it
/// to decide whether to pull a registry image or invoke a local build.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ResolvedSource {
    /// Pull `image` from a registry using `pull_policy` semantics.
    Pull {
        image: String,
        pull_policy: String,
        image_signature: Option<String>,
    },
    /// Build locally. The resulting tag is the image reference for `podman create`.
    Build(BuildConfig),
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(untagged)]
pub enum Dependency {
    Storage {
        storage: String,
    },
    App {
        app_id: String,
        version: Option<String>,
    },
    Simple(String),
}

#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct ResourceLimits {
    #[serde(default)]
    pub cpu_limit: Option<u32>,
    #[serde(default)]
    pub memory_limit: Option<String>,
    #[serde(default)]
    pub disk_limit: Option<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct SecurityPolicy {
    #[serde(default)]
    pub capabilities: Vec<String>,
    #[serde(default = "default_true")]
    pub readonly_root: bool,
    #[serde(default = "default_network_policy")]
    pub network_policy: String,
    #[serde(default)]
    pub apparmor_profile: Option<String>,
}

fn default_true() -> bool {
    true
}

fn default_network_policy() -> String {
    "isolated".to_string()
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PortMapping {
    pub host: u16,
    pub container: u16,
    #[serde(default)]
    pub protocol: String,
}

impl From<(u16, u16)> for PortMapping {
    fn from((host, container): (u16, u16)) -> Self {
        PortMapping {
            host,
            container,
            protocol: "tcp".to_string(),
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Volume {
    #[serde(rename = "type")]
    pub volume_type: String,
    pub source: String,
    pub target: String,
    #[serde(default)]
    pub options: Vec<String>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HealthCheck {
    #[serde(rename = "type")]
    pub check_type: String,
    pub endpoint: Option<String>,
    pub path: Option<String>,
    #[serde(default = "default_interval")]
    pub interval: String,
    #[serde(default = "default_timeout")]
    pub timeout: String,
    #[serde(default = "default_retries")]
    pub retries: u32,
}

fn default_interval() -> String {
    "30s".to_string()
}

fn default_timeout() -> String {
    "5s".to_string()
}

fn default_retries() -> u32 {
    3
}

impl AppManifest {
    pub fn from_file(path: &std::path::Path) -> Result<Self, ManifestError> {
        let content = std::fs::read_to_string(path)?;
        Self::parse(&content)
    }

    pub fn parse(content: &str) -> Result<Self, ManifestError> {
        let manifest: AppManifest = serde_yaml::from_str(content)?;
        manifest.validate()?;
        Ok(manifest)
    }

    pub fn validate(&self) -> Result<(), ManifestError> {
        if self.app.id.is_empty() {
            return Err(ManifestError::Invalid("app.id cannot be empty".to_string()));
        }

        // Exactly one of container.image or container.build must be set. We can't
        // default either side, because an empty-string image or an empty build block
        // would be silently wrong downstream.
        match (&self.app.container.image, &self.app.container.build) {
            (Some(img), None) if !img.is_empty() => {}
            (None, Some(b)) => {
                if b.context.is_empty() {
                    return Err(ManifestError::Invalid(
                        "container.build.context cannot be empty".to_string(),
                    ));
                }
                if b.tag.is_empty() {
                    return Err(ManifestError::Invalid(
                        "container.build.tag cannot be empty".to_string(),
                    ));
                }
            }
            (Some(_), Some(_)) => {
                return Err(ManifestError::Invalid(
                    "container.image and container.build are mutually exclusive".to_string(),
                ));
            }
            _ => {
                return Err(ManifestError::Invalid(
                    "container must specify either image or build".to_string(),
                ));
            }
        }

        // Validate version format (semantic versioning)
        if !self.app.version.chars().any(|c| c.is_ascii_digit()) {
            return Err(ManifestError::Invalid(
                "app.version must contain at least one digit".to_string(),
            ));
        }

        Ok(())
    }
}

impl ContainerConfig {
    /// Collapse the (image, build) pair into a single resolved source.
    ///
    /// Returns `None` if the config is in an invalid state (e.g. neither field set
    /// or both set). Callers should have already run `AppManifest::validate()` to
    /// surface a user-facing error; this method is for internal orchestrator use
    /// after validation has passed.
    pub fn resolve(&self) -> Option<ResolvedSource> {
        match (&self.image, &self.build) {
            (Some(img), None) if !img.is_empty() => Some(ResolvedSource::Pull {
                image: img.clone(),
                pull_policy: self.pull_policy.clone(),
                image_signature: self.image_signature.clone(),
            }),
            (None, Some(b)) => Some(ResolvedSource::Build(b.clone())),
            _ => None,
        }
    }

    /// The image reference used to create/inspect a container for this config.
    ///
    /// For Pull sources this is the registry image. For Build sources this is
    /// the locally-built tag. Returns `None` only for an invalid config.
    pub fn image_ref(&self) -> Option<String> {
        self.resolve().map(|r| match r {
            ResolvedSource::Pull { image, .. } => image,
            ResolvedSource::Build(b) => b.tag,
        })
    }
}

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

    #[test]
    fn test_manifest_parse() {
        let yaml = r#"
app:
  id: test-app
  name: Test App
  version: 1.0.0
  container:
    image: test/image:latest
"#;

        let manifest = AppManifest::parse(yaml).unwrap();
        assert_eq!(manifest.app.id, "test-app");
        assert_eq!(manifest.app.name, "Test App");
        assert_eq!(manifest.app.version, "1.0.0");
    }

    #[test]
    fn test_manifest_validation() {
        let yaml = r#"
app:
  id: ""
  name: Test
  version: 1.0.0
  container:
    image: test/image:latest
"#;

        let result = AppManifest::parse(yaml);
        assert!(result.is_err());
    }

    #[test]
    fn pull_source_resolves_to_pull() {
        let yaml = r#"
app:
  id: test-app
  name: Test
  version: 1.0.0
  container:
    image: docker.io/library/nginx:1.27
    pull_policy: always
"#;
        let m = AppManifest::parse(yaml).unwrap();
        let src = m.app.container.resolve().unwrap();
        match src {
            ResolvedSource::Pull {
                image, pull_policy, ..
            } => {
                assert_eq!(image, "docker.io/library/nginx:1.27");
                assert_eq!(pull_policy, "always");
            }
            _ => panic!("expected Pull"),
        }
        assert_eq!(
            m.app.container.image_ref().as_deref(),
            Some("docker.io/library/nginx:1.27")
        );
    }

    #[test]
    fn build_source_resolves_to_build() {
        let yaml = r#"
app:
  id: bitcoin-ui
  name: Bitcoin UI
  version: 1.0.0
  container:
    build:
      context: /opt/archipelago/docker/bitcoin-ui
      dockerfile: Dockerfile
      tag: archy-bitcoin-ui:local
      build_args:
        NGINX_VERSION: "1.27"
"#;
        let m = AppManifest::parse(yaml).unwrap();
        let src = m.app.container.resolve().unwrap();
        match src {
            ResolvedSource::Build(b) => {
                assert_eq!(b.context, "/opt/archipelago/docker/bitcoin-ui");
                assert_eq!(b.dockerfile, "Dockerfile");
                assert_eq!(b.tag, "archy-bitcoin-ui:local");
                assert_eq!(b.build_args.get("NGINX_VERSION").unwrap(), "1.27");
            }
            _ => panic!("expected Build"),
        }
        assert_eq!(
            m.app.container.image_ref().as_deref(),
            Some("archy-bitcoin-ui:local")
        );
    }

    #[test]
    fn dockerfile_defaults_to_dockerfile() {
        let yaml = r#"
app:
  id: x
  name: X
  version: 1.0.0
  container:
    build:
      context: /tmp
      tag: x:local
"#;
        let m = AppManifest::parse(yaml).unwrap();
        match m.app.container.resolve().unwrap() {
            ResolvedSource::Build(b) => assert_eq!(b.dockerfile, "Dockerfile"),
            _ => unreachable!(),
        }
    }

    #[test]
    fn image_and_build_both_set_is_rejected() {
        let yaml = r#"
app:
  id: x
  name: X
  version: 1.0.0
  container:
    image: foo:latest
    build:
      context: /tmp
      tag: x:local
"#;
        let err = AppManifest::parse(yaml).unwrap_err();
        let msg = format!("{err}");
        assert!(
            msg.contains("mutually exclusive"),
            "unexpected error: {msg}"
        );
    }

    #[test]
    fn neither_image_nor_build_is_rejected() {
        let yaml = r#"
app:
  id: x
  name: X
  version: 1.0.0
  container: {}
"#;
        let err = AppManifest::parse(yaml).unwrap_err();
        let msg = format!("{err}");
        assert!(
            msg.contains("either image or build"),
            "unexpected error: {msg}"
        );
    }

    #[test]
    fn empty_image_string_is_rejected() {
        let yaml = r#"
app:
  id: x
  name: X
  version: 1.0.0
  container:
    image: ""
"#;
        let err = AppManifest::parse(yaml).unwrap_err();
        let msg = format!("{err}");
        assert!(
            msg.contains("either image or build"),
            "unexpected error: {msg}"
        );
    }

    #[test]
    fn empty_build_context_is_rejected() {
        let yaml = r#"
app:
  id: x
  name: X
  version: 1.0.0
  container:
    build:
      context: ""
      tag: x:local
"#;
        let err = AppManifest::parse(yaml).unwrap_err();
        let msg = format!("{err}");
        assert!(msg.contains("context"), "unexpected error: {msg}");
    }

    #[test]
    fn empty_build_tag_is_rejected() {
        let yaml = r#"
app:
  id: x
  name: X
  version: 1.0.0
  container:
    build:
      context: /tmp
      tag: ""
"#;
        let err = AppManifest::parse(yaml).unwrap_err();
        let msg = format!("{err}");
        assert!(msg.contains("tag"), "unexpected error: {msg}");
    }

    #[test]
    fn existing_pull_only_manifests_still_parse() {
        // Backwards-compat smoke: the shape every file in apps/*/manifest.yml uses today.
        let yaml = r#"
app:
  id: legacy
  name: Legacy App
  version: 0.1.0
  description: existing shape
  container:
    image: registry.example.com/legacy:1.2.3
    image_signature: sha256:abc
  ports:
    - { host: 8080, container: 80 }
"#;
        let m = AppManifest::parse(yaml).unwrap();
        assert_eq!(m.app.container.pull_policy, "if-not-present");
        matches!(
            m.app.container.resolve().unwrap(),
            ResolvedSource::Pull { .. }
        );
    }
}