olai-codegen 0.0.1

use std::collections::HashSet;

use convert_case::{Case, Casing};
use quote::format_ident;
use syn::Ident;

use crate::error::{Error, Result};
use crate::google::api::{ResourceDescriptor, http_rule::Pattern};
use crate::parsing::types::UnifiedType;
use crate::parsing::{CodeGenMetadata, HttpPattern, MethodMetadata, OneofVariant};

/// The Operation a method is performing
///
/// There are standard CRUD operations, as well as custom operations.
///
/// Standard operations on collections are:
/// - List: Retrieve a list of resources
/// - Create: Create a new resource
///
/// Standard operations on individual resources are:
/// - Get: Retrieve a single resource
/// - Update: Update an existing resource
/// - Delete: Delete a resource
///
/// Custom operations are:
/// - Custom(Pattern): custom HTTP operation
#[derive(Debug, Clone, PartialEq)]
pub enum RequestType {
    List,
    Create,
    Get,
    Update,
    Delete,
    Custom(Pattern),
}

/// A method that was skipped during analysis due to incomplete metadata.
#[derive(Debug, Clone)]
pub struct SkippedMethod {
    /// Fully-qualified name of the service containing the skipped method.
    pub service_name: String,
    /// Name of the skipped method (e.g. `"GetCatalog"`).
    pub method_name: String,
    /// Human-readable reason the method was skipped (e.g. `"missing HTTP annotation"`).
    pub reason: String,
}

/// High-level plan for what code to generate
#[derive(Debug)]
pub struct GenerationPlan {
    /// Services to generate handlers for
    pub services: Vec<ServicePlan>,
    /// Methods that were excluded from the plan due to incomplete metadata.
    ///
    /// Callers can inspect this list to distinguish "service has zero methods" from "all methods
    /// were skipped due to missing HTTP annotations", and to surface actionable warnings.
    pub skipped_methods: Vec<SkippedMethod>,
}

/// Plan for generating code for a single service
#[derive(Debug, Clone)]
pub struct ServicePlan {
    /// Service name (e.g., "CatalogsService")
    pub service_name: String,
    /// Handler trait name (e.g., "CatalogHandler")
    pub handler_name: String,
    /// Base URL path for this service (e.g., "catalogs")
    pub base_path: String,
    /// Proto package name (e.g., "unitycatalog.catalogs.v1")
    pub package: String,
    /// Methods to generate for this service
    pub methods: Vec<MethodPlan>,
    /// Resources managed by this service
    pub managed_resources: Vec<ManagedResource>,
    /// Documentation from protobuf service comments
    pub documentation: Option<String>,
    /// Ancestor chain for this service's managed resource, derived cross-service from
    /// `resource_reference { child_type }` annotations.
    ///
    /// Entries are ordered **root-first** (shallowest ancestor first). For example, for
    /// a Table service this would be `[catalog_name (depth 0), schema_name (depth 1)]`.
    ///
    /// Empty when no `resource_reference` annotations are present — codegen falls back to
    /// naming heuristics in that case.
    pub hierarchy: Vec<ResourceHierarchy>,
}

/// Plan for generating code for a single method
#[derive(Debug, Clone)]
pub struct MethodPlan {
    /// Original method metadata
    pub metadata: MethodMetadata,
    /// Rust function name for the handler method
    pub handler_function_name: String,
    /// Pre-parsed HTTP URL pattern
    pub http_pattern: HttpPattern,
    /// HTTP method string for routing (e.g., "GET", "POST")
    pub http_method: String,
    /// Parameters passed to the method (path, query, and body)
    pub parameters: Vec<RequestParam>,
    /// Whether this method returns a response body
    pub has_response: bool,
    /// Request type for this method
    pub request_type: RequestType,
    /// The resource type name returned by this method (if any)
    pub output_resource_type: Option<String>,
}

impl MethodPlan {
    pub fn path_parameters(&self) -> impl Iterator<Item = &PathParam> {
        self.parameters.iter().filter_map(|param| match param {
            RequestParam::Path(path_param) => Some(path_param),
            _ => None,
        })
    }

    pub fn query_parameters(&self) -> impl Iterator<Item = &QueryParam> {
        self.parameters.iter().filter_map(|param| match param {
            RequestParam::Query(query_param) => Some(query_param),
            _ => None,
        })
    }

    pub fn body_fields(&self) -> impl Iterator<Item = &BodyField> {
        self.parameters.iter().filter_map(|param| match param {
            RequestParam::Body(body_field) => Some(body_field),
            _ => None,
        })
    }
}

#[derive(Debug, Clone)]
pub enum RequestParam {
    Path(PathParam),
    Query(QueryParam),
    Body(BodyField),
}

impl RequestParam {
    pub fn name(&self) -> &str {
        match self {
            RequestParam::Path(param) => &param.name,
            RequestParam::Query(param) => &param.name,
            RequestParam::Body(param) => &param.name,
        }
    }

    pub fn field_type(&self) -> &UnifiedType {
        match self {
            RequestParam::Path(param) => &param.field_type,
            RequestParam::Query(param) => &param.field_type,
            RequestParam::Body(param) => &param.field_type,
        }
    }

    pub fn field_ident(&self) -> Ident {
        format_ident!("{}", self.name())
    }

    pub fn is_optional(&self) -> bool {
        match self {
            RequestParam::Path(_) => false,
            RequestParam::Query(param) => param.is_optional(),
            RequestParam::Body(param) => param.is_optional(),
        }
    }

    pub fn is_path_param(&self) -> bool {
        matches!(self, RequestParam::Path(_))
    }

    pub fn documentation(&self) -> Option<&str> {
        match self {
            RequestParam::Path(param) => param.documentation.as_deref(),
            RequestParam::Query(param) => param.documentation.as_deref(),
            RequestParam::Body(param) => param.documentation.as_deref(),
        }
    }
}

/// A path parameter in a URL template
#[derive(Debug, Clone)]
pub struct PathParam {
    /// Field name in the request struct (e.g., "full_name")
    pub name: String,
    /// Parsed type of the path parameter
    pub field_type: UnifiedType,
    /// Documentation from protobuf field comments
    pub documentation: Option<String>,
}

impl From<PathParam> for RequestParam {
    fn from(param: PathParam) -> Self {
        RequestParam::Path(param)
    }
}

/// A query parameter for HTTP requests
#[derive(Debug, Clone)]
pub struct QueryParam {
    /// Parameter name
    pub name: String,
    /// Parsed type of the query parameter
    pub field_type: UnifiedType,
    /// Documentation from protobuf field comments
    pub documentation: Option<String>,
    /// Resource reference annotation, if present on the corresponding proto field.
    ///
    /// - `child_type` non-empty: this param scopes a parent of that resource type
    ///   (e.g. `catalog_name` with `child_type = "unitycatalog.io/Schema"`).
    /// - `r#type` non-empty: this param directly identifies a resource of that type.
    pub resource_reference: Option<crate::google::api::ResourceReference>,
}

impl QueryParam {
    /// Denotes if the parameter is optional
    pub fn is_optional(&self) -> bool {
        self.field_type.is_optional
    }
}

impl From<QueryParam> for RequestParam {
    fn from(param: QueryParam) -> Self {
        RequestParam::Query(param)
    }
}

/// A body field that should be extracted from the request body
#[derive(Debug, Clone)]
pub struct BodyField {
    /// Field name
    pub name: String,
    /// Parsed type of the body parameter
    pub field_type: UnifiedType,
    /// Whether this field is a repeated (Vec) type
    pub repeated: bool,
    /// For oneof fields, the variants with their names and types
    pub oneof_variants: Option<Vec<OneofVariant>>,
    /// Documentation from protobuf field comments
    pub documentation: Option<String>,
}

impl BodyField {
    /// Denotes whether this field should be treated as optional in builder APIs.
    ///
    /// A field is optional when its `UnifiedType.is_optional` flag is set, when it is
    /// repeated, or when its base type is `Map`, `Message`, or `OneOf` (complex types
    /// always have a valid default and are therefore optional constructor parameters).
    pub fn is_optional(&self) -> bool {
        use crate::parsing::types::BaseType;
        self.field_type.is_optional
            || self.repeated
            || matches!(
                self.field_type.base_type,
                BaseType::Map(_, _) | BaseType::Message(_) | BaseType::OneOf(_)
            )
    }
}

impl From<BodyField> for RequestParam {
    fn from(field: BodyField) -> Self {
        RequestParam::Body(field)
    }
}

/// Information about a resource managed by a service
#[derive(Debug, Clone)]
pub struct ManagedResource {
    /// Resource type name (e.g., "Catalog")
    pub type_name: String,
    /// Resource descriptor information
    pub descriptor: ResourceDescriptor,
}

/// Describes one ancestor step in a managed resource's parent chain, derived from
/// `google.api.resource_reference { child_type }` annotations on List request fields.
///
/// Entries in [`ServicePlan::hierarchy`] are ordered **root-first** (shallowest ancestor first),
/// so iterating them in order produces the correct param list for resource accessors (e.g.
/// `["catalog_name", "schema_name"]` for a Table, where catalog is depth 0 and schema depth 1).
///
/// Built during analysis via the cross-service global parent map and stored on [`ServicePlan`].
#[derive(Debug, Clone)]
#[non_exhaustive]
pub struct ResourceHierarchy {
    /// The service's managed resource type string (e.g. `"unitycatalog.io/Table"`).
    ///
    /// Note: on flat APIs this equals the `child_type` annotation value, but the *actual*
    /// resource type of the ancestor is `parent_resource_type`, which may differ.
    pub child_resource_type: String,
    /// The actual resource type of the ancestor identified by `parent_field_name`
    /// (e.g. `"unitycatalog.io/Catalog"` for the `catalog_name` field on ListTablesRequest).
    ///
    /// This may differ from `child_resource_type` for grandparent fields on flat APIs
    /// (e.g. `catalog_name` on ListTablesRequest has `child_type = Table` but the field
    /// actually identifies a Catalog resource).
    pub parent_resource_type: String,
    /// The proto field name carrying the ancestor identifier (e.g. `"catalog_name"`).
    pub parent_field_name: String,
    /// The singular name of the ancestor resource (e.g. `"catalog"`), resolved by stripping
    /// `"_name"` from `parent_field_name` and matching against known resource descriptors.
    /// `None` when the singular cannot be resolved.
    pub parent_singular: Option<String>,
}

/// Classifies an RPC method as a standard CRUD operation or custom operation.
///
/// This is an internal helper used by [`super::analyze_method`]. Construct via
/// [`MethodPlanner::try_new`] and consume with [`MethodPlanner::request_type`] and
/// [`MethodPlanner::http_pattern`].
pub(crate) struct MethodPlanner<'a> {
    method: &'a MethodMetadata,
    pattern: Pattern,
    path: HttpPattern,
    metadata: &'a CodeGenMetadata,
}

impl<'a> MethodPlanner<'a> {
    pub(crate) fn try_new(
        method: &'a MethodMetadata,
        metadata: &'a CodeGenMetadata,
    ) -> Result<Self> {
        let Some(pattern) = &method.http_rule.pattern else {
            return Err(Error::MissingAnnotation {
                object: method.method_name.clone(),
                message: "Missing HTTP rule pattern".to_string(),
            });
        };
        Ok(Self {
            method,
            path: method.http_pattern.clone(),
            pattern: pattern.clone(),
            metadata,
        })
    }

    /// Consume the planner and return the pre-parsed HTTP URL pattern.
    pub(crate) fn into_http_pattern(self) -> HttpPattern {
        self.path
    }

    /// Classify the RPC as a standard CRUD operation per Google AIP 131-135.
    ///
    /// Each standard operation is identified by matching (verb, HTTP method, path shape,
    /// resource lookup). See:
    /// - [AIP-131](https://google.aip.dev/131) Get
    /// - [AIP-132](https://google.aip.dev/132) List
    /// - [AIP-133](https://google.aip.dev/133) Create
    /// - [AIP-134](https://google.aip.dev/134) Update
    /// - [AIP-135](https://google.aip.dev/135) Delete
    pub(crate) fn request_type(&self) -> RequestType {
        let snake_name = self.method.method_name.to_case(Case::Snake);
        let verb_resource = snake_name.split_once('_');

        if let Some((verb, resource)) = verb_resource {
            // Table of (verb, expected pattern, path must end with parameter?, lookup by plural?)
            #[allow(clippy::type_complexity)]
            let standard_ops: &[(
                &str,
                fn(&Pattern) -> bool,
                bool,
                bool,
                RequestType,
            )] = &[
                (
                    "get",
                    |p| matches!(p, Pattern::Get(_)),
                    true,
                    false,
                    RequestType::Get,
                ),
                (
                    "list",
                    |p| matches!(p, Pattern::Get(_)),
                    false,
                    true,
                    RequestType::List,
                ),
                (
                    "create",
                    |p| matches!(p, Pattern::Post(_)),
                    false,
                    false,
                    RequestType::Create,
                ),
                (
                    "update",
                    |p| matches!(p, Pattern::Patch(_)),
                    true,
                    false,
                    RequestType::Update,
                ),
                (
                    "delete",
                    |p| matches!(p, Pattern::Delete(_)),
                    true,
                    false,
                    RequestType::Delete,
                ),
            ];

            for &(expected_verb, pattern_check, ends_with_param, use_plural, ref result_type) in
                standard_ops
            {
                if verb != expected_verb || !pattern_check(&self.pattern) {
                    continue;
                }
                if ends_with_param && self.path.ends_with_static() {
                    continue;
                }
                if !ends_with_param && self.path.ends_with_parameter() {
                    continue;
                }
                let found = if use_plural {
                    self.metadata.resource_from_plural(resource).is_some()
                } else {
                    self.metadata.resource_from_singular(resource).is_some()
                };
                if found {
                    return result_type.clone();
                }
            }
        }

        RequestType::Custom(self.pattern.clone())
    }

    pub(crate) fn has_response(&self) -> bool {
        !self.method.output_type.is_empty() && !self.method.output_type.ends_with("Empty")
    }

    /// Extract the simple resource type name from the method's output type.
    ///
    /// Strips the package prefix (e.g., `.example.catalog.v1.Catalog` → `Catalog`).
    pub(crate) fn output_resource_type(&self) -> Option<String> {
        if self.has_response() {
            let output_type = &self.method.output_type;
            let simple = output_type
                .rfind('.')
                .map(|i| &output_type[i + 1..])
                .unwrap_or(output_type);
            Some(simple.to_string())
        } else {
            None
        }
    }
}

/// Split body fields from a `MethodPlan` into required and optional subsets.
///
/// Delegates to [`BodyField::is_optional`] for the classification. Optional fields
/// become `with_*` setter methods; required fields become constructor parameters.
pub fn split_body_fields(plan: &MethodPlan) -> (Vec<&BodyField>, Vec<&BodyField>) {
    let mut required = Vec::new();
    let mut optional = Vec::new();
    for field in plan.body_fields() {
        if field.is_optional() {
            optional.push(field);
        } else {
            required.push(field);
        }
    }
    (required, optional)
}

/// Extract managed resources from service methods, deduplicating by type name.
pub fn extract_managed_resources(
    metadata: &CodeGenMetadata,
    methods: &[MethodPlan],
) -> Vec<ManagedResource> {
    let mut resources = Vec::new();
    let mut seen_types = HashSet::<String>::new();

    for method in methods {
        if let Some(ref resource_type) = method.output_resource_type {
            if seen_types.contains(resource_type) {
                continue;
            }
            if let Some(descriptor) = metadata.get_resource_descriptor(resource_type) {
                resources.push(ManagedResource {
                    type_name: resource_type.clone(),
                    descriptor: descriptor.clone(),
                });
                seen_types.insert(resource_type.clone());
            }
        }
    }

    resources
}