atrg-codegen 0.1.0

//! Code generation from lexicon definitions.

use std::path::Path;

use convert_case::{Case, Casing};

use crate::lexicon::{self, LexiconDef, LexiconDoc, LexiconProperty};

/// Options for code generation.
#[derive(Debug, Clone)]
pub struct GenOptions {
    /// Whether to generate handler stubs (default: true).
    pub generate_stubs: bool,
    /// Whether to generate route wiring (default: true).
    pub generate_routes: bool,
}

impl Default for GenOptions {
    fn default() -> Self {
        Self {
            generate_stubs: true,
            generate_routes: true,
        }
    }
}

/// Report from a code generation run.
#[derive(Debug)]
pub struct GenReport {
    /// Number of lexicon files processed.
    pub files_processed: usize,
    /// Number of types generated.
    pub types_generated: usize,
    /// Number of handler stubs generated.
    pub stubs_generated: usize,
    /// Paths of generated files.
    pub output_files: Vec<String>,
}

/// Generate Rust code from lexicon JSON files.
///
/// Walks `input_dir` for `*.json` files, parses each as a lexicon,
/// and writes generated Rust code to `output_dir`.
pub fn generate(
    input_dir: &Path,
    output_dir: &Path,
    opts: GenOptions,
) -> anyhow::Result<GenReport> {
    let mut report = GenReport {
        files_processed: 0,
        types_generated: 0,
        stubs_generated: 0,
        output_files: vec![],
    };

    // Collect all lexicon files
    let mut lexicons: Vec<LexiconDoc> = Vec::new();

    for entry in walkdir::WalkDir::new(input_dir)
        .into_iter()
        .filter_map(|e| e.ok())
        .filter(|e| e.path().extension().is_some_and(|ext| ext == "json"))
    {
        let content = std::fs::read_to_string(entry.path())?;
        match lexicon::parse_lexicon(&content) {
            Ok(doc) => {
                tracing::debug!(id = %doc.id, path = %entry.path().display(), "parsed lexicon");
                lexicons.push(doc);
                report.files_processed += 1;
            }
            Err(e) => {
                anyhow::bail!(
                    "Failed to parse lexicon at {}: {}",
                    entry.path().display(),
                    e
                );
            }
        }
    }

    if lexicons.is_empty() {
        tracing::warn!(dir = %input_dir.display(), "no lexicon JSON files found");
        return Ok(report);
    }

    // Generate code for each lexicon
    std::fs::create_dir_all(output_dir)?;

    let mut all_types = String::new();
    let mut all_routes = Vec::new();

    for doc in &lexicons {
        let (types_code, route_entries, type_count, stub_count) = generate_for_lexicon(doc, &opts)?;
        all_types.push_str(&types_code);
        all_types.push('\n');
        all_routes.extend(route_entries);
        report.types_generated += type_count;
        report.stubs_generated += stub_count;
    }

    // Write types module
    let types_path = output_dir.join("types.rs");
    let types_content = format!(
        "//! Generated types from AT Protocol lexicons.\n\
         //!\n\
         //! DO NOT EDIT — this file is generated by `atrg generate`.\n\n\
         use serde::{{Deserialize, Serialize}};\n\n\
         {all_types}"
    );
    let formatted = format_code(&types_content);
    std::fs::write(&types_path, &formatted)?;
    report.output_files.push(types_path.display().to_string());

    // Write routes module (if enabled)
    if opts.generate_routes && !all_routes.is_empty() {
        let routes_code = generate_routes_module(&all_routes);
        let routes_path = output_dir.join("routes.rs");
        let formatted = format_code(&routes_code);
        std::fs::write(&routes_path, &formatted)?;
        report.output_files.push(routes_path.display().to_string());
    }

    // Write mod.rs
    let mod_path = output_dir.join("mod.rs");
    let mut mod_content = String::from(
        "//! Generated code from AT Protocol lexicons.\n\
         //!\n\
         //! DO NOT EDIT — this file is generated by `atrg generate`.\n\n\
         pub mod types;\n",
    );
    if opts.generate_routes && !all_routes.is_empty() {
        mod_content.push_str("pub mod routes;\n");
    }
    std::fs::write(&mod_path, &mod_content)?;
    report.output_files.push(mod_path.display().to_string());

    tracing::info!(
        files = report.files_processed,
        types = report.types_generated,
        stubs = report.stubs_generated,
        "code generation complete"
    );

    Ok(report)
}

/// A route entry for the generated routes module.
struct RouteEntry {
    nsid: String,
    method: &'static str, // "get" or "post"
    handler_name: String,
}

fn generate_for_lexicon(
    doc: &LexiconDoc,
    opts: &GenOptions,
) -> anyhow::Result<(String, Vec<RouteEntry>, usize, usize)> {
    let mut code = String::new();
    let mut routes = Vec::new();
    let mut type_count = 0;
    let mut stub_count = 0;

    let type_prefix = nsid_to_type_prefix(&doc.id);

    for (def_name, def) in &doc.defs {
        match def {
            LexiconDef::Record {
                description,
                record: Some(obj),
                ..
            } => {
                let struct_name = if def_name == "main" {
                    format!("{type_prefix}Record")
                } else {
                    format!("{type_prefix}{}", def_name.to_case(Case::Pascal))
                };
                code.push_str(&generate_struct(&struct_name, description.as_deref(), obj));
                type_count += 1;
            }
            LexiconDef::Object(obj) => {
                let struct_name = if def_name == "main" {
                    type_prefix.clone()
                } else {
                    format!("{type_prefix}{}", def_name.to_case(Case::Pascal))
                };
                code.push_str(&generate_struct(
                    &struct_name,
                    obj.description.as_deref(),
                    obj,
                ));
                type_count += 1;
            }
            LexiconDef::Query {
                description: _,
                parameters,
                output,
            } => {
                // Generate params struct
                if let Some(params) = parameters {
                    let name = format!("{type_prefix}Params");
                    code.push_str(&generate_struct(&name, None, params));
                    type_count += 1;
                }
                // Generate output struct
                if let Some(out) = output {
                    if let Some(schema) = &out.schema {
                        let name = format!("{type_prefix}Output");
                        code.push_str(&generate_struct(&name, None, schema));
                        type_count += 1;
                    }
                }
                if opts.generate_stubs && def_name == "main" {
                    let handler = nsid_to_handler_name(&doc.id);
                    routes.push(RouteEntry {
                        nsid: doc.id.clone(),
                        method: "get",
                        handler_name: handler,
                    });
                    stub_count += 1;
                }
            }
            LexiconDef::Procedure {
                description: _,
                input,
                output,
            } => {
                // Generate input struct
                if let Some(inp) = input {
                    if let Some(schema) = &inp.schema {
                        let name = format!("{type_prefix}Input");
                        code.push_str(&generate_struct(&name, None, schema));
                        type_count += 1;
                    }
                }
                // Generate output struct
                if let Some(out) = output {
                    if let Some(schema) = &out.schema {
                        let name = format!("{type_prefix}Output");
                        code.push_str(&generate_struct(&name, None, schema));
                        type_count += 1;
                    }
                }
                if opts.generate_stubs && def_name == "main" {
                    let handler = nsid_to_handler_name(&doc.id);
                    routes.push(RouteEntry {
                        nsid: doc.id.clone(),
                        method: "post",
                        handler_name: handler,
                    });
                    stub_count += 1;
                }
            }
            _ => {}
        }
    }

    Ok((code, routes, type_count, stub_count))
}

fn generate_struct(name: &str, description: Option<&str>, obj: &lexicon::LexiconObject) -> String {
    let mut s = String::new();

    if let Some(desc) = description {
        s.push_str(&format!("/// {desc}\n"));
    }
    s.push_str("#[derive(Debug, Clone, Serialize, Deserialize)]\n");
    s.push_str(&format!("pub struct {name} {{\n"));

    // Sort properties for deterministic output
    let mut props: Vec<_> = obj.properties.iter().collect();
    props.sort_by_key(|(k, _)| *k);

    for (field_name, prop) in &props {
        let rust_name = field_name.to_case(Case::Snake);
        let rust_type = property_to_rust_type(prop, obj.required.contains(*field_name));

        if let Some(desc) = &prop.description {
            s.push_str(&format!("    /// {desc}\n"));
        }

        if rust_name != **field_name {
            s.push_str(&format!("    #[serde(rename = \"{field_name}\")]\n"));
        }

        if !obj.required.contains(*field_name) {
            s.push_str("    #[serde(default, skip_serializing_if = \"Option::is_none\")]\n");
        }

        s.push_str(&format!("    pub {rust_name}: {rust_type},\n"));
    }

    s.push_str("}\n\n");
    s
}

fn property_to_rust_type(prop: &LexiconProperty, required: bool) -> String {
    let base = match prop.prop_type.as_str() {
        "string" => "String".to_string(),
        "integer" => "i64".to_string(),
        "boolean" => "bool".to_string(),
        "blob" => "serde_json::Value".to_string(),
        "unknown" => "serde_json::Value".to_string(),
        "cid-link" => "String".to_string(),
        "array" => {
            if let Some(items) = &prop.items {
                format!("Vec<{}>", property_to_rust_type(items, true))
            } else {
                "Vec<serde_json::Value>".to_string()
            }
        }
        "ref" | "union" => "serde_json::Value".to_string(),
        _ => "serde_json::Value".to_string(),
    };

    if required {
        base
    } else {
        format!("Option<{base}>")
    }
}

fn generate_routes_module(routes: &[RouteEntry]) -> String {
    let mut s = String::from(
        "//! Generated XRPC route wiring.\n\
         //!\n\
         //! DO NOT EDIT — this file is generated by `atrg generate`.\n\n\
         use axum::{Router, routing::{get, post}, Json};\n\
         use atrg_core::AppState;\n\
         use atrg_xrpc::XrpcError;\n\n\
         /// Mount all generated XRPC routes.\n\
         pub fn xrpc_routes() -> Router<AppState> {\n\
         \x20   atrg_xrpc::xrpc_router()\n",
    );

    for route in routes {
        let method = route.method;
        s.push_str(&format!(
            "        .route(\"/xrpc/{}\", {method}({}))\n",
            route.nsid, route.handler_name
        ));
    }

    s.push_str("}\n\n");

    // Generate stub handlers
    for route in routes {
        s.push_str(&format!(
            "/// Stub handler for `{}`.\n\
             ///\n\
             /// TODO: Implement this handler.\n\
             async fn {}() -> Result<Json<serde_json::Value>, XrpcError> {{\n\
             \x20   todo!(\"implement {}\")\n\
             }}\n\n",
            route.nsid, route.handler_name, route.nsid
        ));
    }

    s
}

fn nsid_to_type_prefix(nsid: &str) -> String {
    nsid.split('.')
        .map(|s| s.to_case(Case::Pascal))
        .collect::<Vec<_>>()
        .join("")
}

fn nsid_to_handler_name(nsid: &str) -> String {
    nsid.split('.')
        .next_back()
        .unwrap_or(nsid)
        .to_case(Case::Snake)
}

fn format_code(code: &str) -> String {
    match syn::parse_file(code) {
        Ok(syntax_tree) => prettyplease::unparse(&syntax_tree),
        Err(_) => {
            tracing::warn!("generated code could not be parsed by syn; skipping formatting");
            code.to_string()
        }
    }
}

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

    fn setup_fixture(dir: &Path, files: &[(&str, &str)]) {
        fs::create_dir_all(dir).unwrap();
        for (name, content) in files {
            fs::write(dir.join(name), content).unwrap();
        }
    }

    #[test]
    fn generate_from_query_lexicon() {
        let input = tempfile::tempdir().unwrap();
        let output = tempfile::tempdir().unwrap();

        let lexicon = r#"{
            "lexicon": 1,
            "id": "com.atrg.test.ping",
            "defs": {
                "main": {
                    "type": "query",
                    "description": "Test ping",
                    "output": {
                        "encoding": "application/json",
                        "schema": {
                            "type": "object",
                            "required": ["pong"],
                            "properties": {
                                "pong": { "type": "boolean" },
                                "echo": { "type": "string" }
                            }
                        }
                    }
                }
            }
        }"#;

        setup_fixture(input.path(), &[("ping.json", lexicon)]);

        let report = generate(input.path(), output.path(), GenOptions::default()).unwrap();
        assert_eq!(report.files_processed, 1);
        assert!(report.types_generated >= 1);
        assert_eq!(report.stubs_generated, 1);

        // Verify types.rs was generated
        let types = fs::read_to_string(output.path().join("types.rs")).unwrap();
        assert!(types.contains("ComAtrgTestPingOutput"));
        assert!(types.contains("pub pong: bool"));
    }

    #[test]
    fn generate_from_record_lexicon() {
        let input = tempfile::tempdir().unwrap();
        let output = tempfile::tempdir().unwrap();

        let lexicon = r#"{
            "lexicon": 1,
            "id": "com.atrg.test.post",
            "defs": {
                "main": {
                    "type": "record",
                    "description": "A test post",
                    "key": "tid",
                    "record": {
                        "type": "object",
                        "required": ["text", "createdAt"],
                        "properties": {
                            "text": { "type": "string", "max_length": 3000 },
                            "createdAt": { "type": "string", "format": "datetime" }
                        }
                    }
                }
            }
        }"#;

        setup_fixture(input.path(), &[("post.json", lexicon)]);

        let report = generate(input.path(), output.path(), GenOptions::default()).unwrap();
        assert_eq!(report.files_processed, 1);
        assert!(report.types_generated >= 1);

        let types = fs::read_to_string(output.path().join("types.rs")).unwrap();
        assert!(types.contains("ComAtrgTestPostRecord"));
        assert!(types.contains("pub text: String"));
    }

    #[test]
    fn malformed_lexicon_gives_error() {
        let input = tempfile::tempdir().unwrap();
        let output = tempfile::tempdir().unwrap();

        setup_fixture(input.path(), &[("bad.json", "not valid json")]);

        let result = generate(input.path(), output.path(), GenOptions::default());
        assert!(result.is_err());
        let err = result.unwrap_err().to_string();
        assert!(
            err.contains("bad.json"),
            "error should mention the file: {err}"
        );
    }

    #[test]
    fn empty_dir_produces_empty_report() {
        let input = tempfile::tempdir().unwrap();
        let output = tempfile::tempdir().unwrap();

        let report = generate(input.path(), output.path(), GenOptions::default()).unwrap();
        assert_eq!(report.files_processed, 0);
    }
}