Here's an updated full project specification including:
	1.	✅ Unified builder for both creation and filtering
	2.	✅ with_...() methods used for both creation and filtering
	3.	✅ Auto-generated CRUD + list + filter + find methods
	4.	✅ Database interface for persistence operations
	5.	✅ Auto-generated registration code
	6.	✅ 📜 Example Rhai script
	7.	✅ 🔍 build.rs should output to src/gen/meeting_builder.rs

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🧾 Project Spec: Rust → Rhai Builder Code Generator

🎯 Goal

Build a build.rs script that parses Rust structs annotated with #[builder] and generates Rhai-compatible unified builders with with_...() methods that populate a single field map used for both creation and filtering. Also generate CRUD operations that use a database interface.

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📥 Input Example: src/models.rs

#[derive(Debug)]
pub struct Meeting {
    pub id: String,
    pub title: String,
    pub description: String,
    pub participants: Vec<String>,
    pub start: String,
}

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📤 Generated Code: src/gen/meeting_builder.rs

✅ 1. MeetingBuilder Struct

#[derive(Clone)]
pub struct MeetingBuilder {
    pub fields: std::collections::HashMap<String, rhai::Dynamic>,
}

✅ 2. with_...() Methods (for each field)

impl MeetingBuilder {
    pub fn with_title(mut self, value: &str) -> Self {
        self.fields.insert("title".into(), value.into());
        self
    }

    pub fn with_participants(mut self, value: Vec<rhai::Dynamic>) -> Self {
        self.fields.insert("participants".into(), value.into());
        self
    }

    pub fn get_fields(&mut self) -> rhai::Map {
        self.fields.clone()
    }
    
    // CRUD operations
    pub fn create(&mut self, db: &dyn Database) -> rhai::Dynamic {
        db.create("meetings", self.get_fields())
    }
    
    pub fn find_by_id(&mut self, db: &dyn Database, id: &str) -> rhai::Dynamic {
        db.find_by_id("meetings", id)
    }
    
    pub fn update(&mut self, db: &dyn Database, id: &str) -> rhai::Dynamic {
        db.update("meetings", id, self.get_fields())
    }
    
    pub fn delete(&mut self, db: &dyn Database, id: &str) -> rhai::Dynamic {
        db.delete("meetings", id)
    }
    
    pub fn list(&mut self, db: &dyn Database) -> rhai::Dynamic {
        db.list("meetings")
    }
    
    pub fn filter(&mut self, db: &dyn Database) -> rhai::Dynamic {
        db.filter("meetings", self.get_fields())
    }
    
    pub fn find(&mut self, db: &dyn Database) -> rhai::Dynamic {
        db.find("meetings", self.get_fields())
    }
}

✅ 3. Database Interface

pub trait Database {
    fn create(&self, collection: &str, fields: rhai::Map) -> rhai::Dynamic;
    fn find_by_id(&self, collection: &str, id: &str) -> rhai::Dynamic;
    fn update(&self, collection: &str, id: &str, fields: rhai::Map) -> rhai::Dynamic;
    fn delete(&self, collection: &str, id: &str) -> rhai::Dynamic;
    fn list(&self, collection: &str) -> rhai::Dynamic;
    fn filter(&self, collection: &str, query: rhai::Map) -> rhai::Dynamic;
    fn find(&self, collection: &str, query: rhai::Map) -> rhai::Dynamic;
}

✅ 4. Rhai Registration

pub fn register_meeting_module(engine: &mut rhai::Engine) {
    engine.register_type::<MeetingBuilder>();
    engine.register_fn("meeting", MeetingBuilder::new);

    engine.register_fn("with_title", MeetingBuilder::with_title);
    engine.register_fn("with_participants", MeetingBuilder::with_participants);
    engine.register_fn("get_fields", MeetingBuilder::get_fields);
    
    // Register CRUD operations
    engine.register_fn("create", MeetingBuilder::create);
    engine.register_fn("find_by_id", MeetingBuilder::find_by_id);
    engine.register_fn("update", MeetingBuilder::update);
    engine.register_fn("delete", MeetingBuilder::delete);
    engine.register_fn("list", MeetingBuilder::list);
    engine.register_fn("filter", MeetingBuilder::filter);
    engine.register_fn("find", MeetingBuilder::find);
}

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✅ Example Rhai Script

// Create a meeting
let meeting_id = meeting()
  .with_title("Project Sync")
  .with_description("Check in with the team")
  .with_participants(["timur", "eda"])
  .with_start("2024-06-01T10:00")
  .create(db);

// Find a meeting by ID
let meeting = meeting().find_by_id(db, meeting_id);

// Update a meeting
meeting()
  .with_description("Updated description")
  .update(db, meeting_id);

// Delete a meeting
meeting().delete(db, meeting_id);

// List all meetings
let all_meetings = meeting().list(db);

// Filter meetings by description
let filtered_meetings = meeting()
  .with_description("Project Sync")
  .filter(db);

// Find a specific meeting
let found_meeting = meeting()
  .with_title("Project Sync")
  .with_start("2024-06-01T10:00")
  .find(db);

This script uses the same builder for all operations.

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📂 Output File

Write generated code to:

src/gen/meeting_builder.rs

And include it in main.rs:

#[path = "gen/meeting_builder.rs"]
mod meeting_builder;

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🔨 build.rs Responsibilities
	•	Use syn to parse src/models.rs
	•	Extract structs and fields
	•	Generate:
	•	MeetingBuilder struct with fields map
	•	All with_...() methods for Rhai
	•	get_fields() method
	•	CRUD + list + filter + find methods
	•	Database trait
	•	register_meeting_module(engine: &mut Engine) function

Output to src/gen/meeting_builder.rs.

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✅ Success Criteria
	•	No duplication between filter/create logic
	•	Fluent API in Rhai
	•	Generated code compiles and integrates
	•	build.rs works as part of standard Rust build pipeline
	•	Easy to extend to more models (e.g., User, Task)
	•	Complete CRUD operations available
	•	Database abstraction for persistence

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