macroforge_ts 0.1.78

//! # Debug Macro Implementation
//!
//! The `Debug` macro generates a human-readable `toString()` method for
//! TypeScript classes, interfaces, enums, and type aliases.
//!
//! ## Generated Output
//!
//! **Classes**: Generates a standalone function `{className}ToString(value)` and a static wrapper
//! method `static toString(value)` returning a string like `"ClassName { field1: value1, field2: value2 }"`.
//!
//! **Enums**: Generates a standalone function `{enumName}ToString(value)` that performs
//! reverse lookup on numeric enums.
//!
//! **Interfaces**: Generates a standalone function `{ifaceName}ToString(value)`.
//!
//! **Type Aliases**: Generates a standalone function using JSON.stringify for
//! complex types, or field enumeration for object types.
//!
//! Names use **camelCase** conversion (e.g., `User` → `userToString`).
//!
//!
//! ## Field-Level Options
//!
//! The `@debug` decorator supports:
//!
//! - `skip` - Exclude the field from debug output
//! - `rename = "label"` - Use a custom label instead of the field name
//!
//! ## Example
//!
//! ```typescript
//! /** @derive(Debug) */
//! class User {
//!     /** @debug({ rename: "id" }) */
//!     userId: number;
//!
//!     /** @debug({ skip: true }) */
//!     password: string;
//!
//!     email: string;
//! }
//! ```
//!
//! Generated output:
//!
//! ```typescript
//! class User {
//!     userId: number;
//!
//!     password: string;
//!
//!     email: string;
//!
//!     static toString(value: User): string {
//!         return userToString(value);
//!     }
//! }
//!
//! export function userToString(value: User): string {
//!     const parts: string[] = [];
//!     parts.push('id: ' + value.userId);
//!     parts.push('email: ' + value.email);
//!     return 'User { ' + parts.join(', ') + ' }';
//! }
//! ```

use convert_case::{Case, Casing};

use crate::builtin::derive_common::{collection_element_type, standalone_fn_name, type_has_derive};
use crate::macros::{ts_macro_derive, ts_template};
use crate::swc_ecma_ast::Expr;
use crate::ts_syn::abi::ir::type_registry::{ResolvedTypeRef, TypeRegistry};
use crate::ts_syn::ts_ident;
use crate::ts_syn::{Data, DeriveInput, MacroforgeError, TsStream, parse_ts_macro_input};

/// Options parsed from @Debug decorator on fields
#[derive(Default)]
struct DebugFieldOptions {
    skip: bool,
    rename: Option<String>,
}

impl DebugFieldOptions {
    fn from_decorators(decorators: &[crate::ts_syn::abi::DecoratorIR]) -> Self {
        let mut opts = DebugFieldOptions::default();
        for decorator in decorators {
            if !decorator.name.eq_ignore_ascii_case("debug") {
                continue;
            }

            let args = decorator.args_src.trim();
            if args.is_empty() {
                continue;
            }

            if has_flag(args, "skip") {
                opts.skip = true;
            }

            if let Some(rename) = extract_named_string(args, "rename") {
                opts.rename = Some(rename);
            }
        }
        opts
    }
}

fn has_flag(args: &str, flag: &str) -> bool {
    if flag_explicit_false(args, flag) {
        return false;
    }

    args.split(|c: char| !c.is_alphanumeric() && c != '_')
        .any(|token| token.eq_ignore_ascii_case(flag))
}

fn flag_explicit_false(args: &str, flag: &str) -> bool {
    let lower = args.to_ascii_lowercase();
    let condensed: String = lower.chars().filter(|c| !c.is_whitespace()).collect();
    condensed.contains(&format!("{flag}:false")) || condensed.contains(&format!("{flag}=false"))
}

fn extract_named_string(args: &str, name: &str) -> Option<String> {
    let lower = args.to_ascii_lowercase();
    let idx = lower.find(name)?;
    let remainder = &args[idx + name.len()..];
    let remainder = remainder.trim_start();

    if remainder.starts_with(':') || remainder.starts_with('=') {
        let value = remainder[1..].trim_start();
        return parse_string_literal(value);
    }

    if remainder.starts_with('(')
        && let Some(close) = remainder.rfind(')')
    {
        let inner = remainder[1..close].trim();
        return parse_string_literal(inner);
    }

    None
}

fn parse_string_literal(input: &str) -> Option<String> {
    let trimmed = input.trim();
    let mut chars = trimmed.chars();
    let quote = chars.next()?;
    if quote != '"' && quote != '\'' {
        return None;
    }

    let mut escaped = false;
    let mut buf = String::new();
    for c in chars {
        if escaped {
            buf.push(c);
            escaped = false;
            continue;
        }
        if c == '\\' {
            escaped = true;
            continue;
        }
        if c == quote {
            return Some(buf);
        }
        buf.push(c);
    }
    None
}

/// Debug field info: (label, field_name, ts_type)
type DebugField = (String, String, String);

/// Generate a debug value expression for a field.
/// When the field type has @derive(Debug), calls the standalone toString function.
fn debug_value_expr(
    field_name: &str,
    _ts_type: &str,
    var: &str,
    resolved: Option<&ResolvedTypeRef>,
    registry: Option<&TypeRegistry>,
) -> String {
    let access = format!("{var}.{field_name}");

    if let (Some(resolved), Some(registry)) = (resolved, registry) {
        // Direct known Debug type → call standalone toString function
        if !resolved.is_collection
            && resolved.registry_key.is_some()
            && type_has_derive(registry, &resolved.base_type_name, "Debug")
        {
            let fn_name = standalone_fn_name(&resolved.base_type_name, "ToString");
            return format!("{fn_name}({access})");
        }

        // Array of known Debug type → map toString
        if resolved.is_collection
            && let Some(elem) = collection_element_type(resolved)
            && elem.registry_key.is_some()
            && type_has_derive(registry, &elem.base_type_name, "Debug")
        {
            let elem_fn = standalone_fn_name(&elem.base_type_name, "ToString");
            return format!("'[' + {access}.map(v => {elem_fn}(v)).join(', ') + ']'");
        }
    }

    // Fallback: string concatenation (original behavior)
    access
}

#[ts_macro_derive(
    Debug,
    description = "Generates a toString() method for debugging",
    attributes((debug, "Configure debug output for this field. Options: skip (exclude from output), rename (custom label)"))
)]
pub fn derive_debug_macro(mut input: TsStream) -> Result<TsStream, MacroforgeError> {
    let input = parse_ts_macro_input!(input as DeriveInput);
    let resolved_fields = input.context.resolved_fields.as_ref();
    let type_registry = input.context.type_registry.as_ref();

    match &input.data {
        Data::Class(class) => {
            let class_name = input.name();
            let class_ident = ts_ident!(class_name);

            // Collect fields that should be included in debug output
            let debug_fields: Vec<DebugField> = class
                .fields()
                .iter()
                .filter_map(|field| {
                    let opts = DebugFieldOptions::from_decorators(&field.decorators);
                    if opts.skip {
                        return None;
                    }
                    let label = opts.rename.unwrap_or_else(|| field.name.clone());
                    Some((label, field.name.clone(), field.ts_type.clone()))
                })
                .collect();

            // Generate function name (always prefix style)
            let fn_name_ident = ts_ident!("{}ToString", class_name.to_case(Case::Camel));
            let fn_name_expr: Expr = fn_name_ident.clone().into();

            // Build push statements with type-aware value expressions
            let mut push_stmts = String::new();
            for (label, name, ts_type) in &debug_fields {
                let resolved = resolved_fields.and_then(|rf| rf.get(name));
                let val_expr = debug_value_expr(name, ts_type, "value", resolved, type_registry);
                push_stmts.push_str(&format!("parts.push(\"{label}: \" + {val_expr});\n"));
            }

            // Generate standalone function with value parameter
            let standalone = if debug_fields.is_empty() {
                ts_template! {
                    export function @{fn_name_ident}(value: @{class_ident.clone()}): string {
                        return "@{class_name} {}";
                    }
                }
            } else {
                ts_template! {
                    export function @{fn_name_ident}(value: @{class_ident.clone()}): string {
                        const parts: string[] = [];
                        {$typescript TsStream::from_string(push_stmts)}
                        return "@{class_name} { " + parts.join(", ") + " }";
                    }
                }
            };

            // Generate static wrapper method that delegates to standalone function
            let class_body = ts_template!(Within {
                static toString(value: @{class_ident.clone()}): string {
                    return @{fn_name_expr}(value);
                }
            });

            // Combine standalone function with class body using {$typescript}
            // The standalone output (no marker) must come FIRST so it defaults to "below" (after class)
            // The body! output has /* @macroforge:body */ marker for class body insertion
            Ok(ts_template! {
                {$typescript standalone}
                {$typescript class_body}
            })
        }
        Data::Enum(enum_data) => {
            let enum_name = input.name();
            let enum_ident = ts_ident!(enum_name);
            let _variants: Vec<String> = enum_data
                .variants()
                .iter()
                .map(|v| v.name.clone())
                .collect();

            let fn_name_ident = ts_ident!("{}ToString", enum_name.to_case(Case::Camel));
            // Convert ident to expression for array access
            let enum_expr: Expr = enum_ident.clone().into();
            Ok(ts_template! {
                export function @{fn_name_ident}(value: @{enum_ident.clone()}): string {
                    {#if !_variants.is_empty()}
                        const key = @{enum_expr.clone()}[value as unknown as keyof typeof @{enum_ident.clone()}];
                        if (key !== undefined) {
                            return "@{enum_name}." + key;
                        }
                        return "@{enum_name}(" + String(value) + ")";
                    {:else}
                        return "@{enum_name}(" + String(value) + ")";
                    {/if}
                }
            })
        }
        Data::Interface(interface) => {
            let interface_name = input.name();
            let interface_ident = ts_ident!(interface_name);

            // Collect fields that should be included in debug output
            let debug_fields: Vec<DebugField> = interface
                .fields()
                .iter()
                .filter_map(|field| {
                    let opts = DebugFieldOptions::from_decorators(&field.decorators);
                    if opts.skip {
                        return None;
                    }
                    let label = opts.rename.unwrap_or_else(|| field.name.clone());
                    Some((label, field.name.clone(), field.ts_type.clone()))
                })
                .collect();

            let fn_name_ident = ts_ident!("{}ToString", interface_name.to_case(Case::Camel));

            if debug_fields.is_empty() {
                Ok(ts_template! {
                    export function @{fn_name_ident}(value: @{interface_ident.clone()}): string {
                        return "@{interface_name} {}";
                    }
                })
            } else {
                let mut push_stmts = String::new();
                for (label, name, ts_type) in &debug_fields {
                    let resolved = resolved_fields.and_then(|rf| rf.get(name));
                    let val_expr =
                        debug_value_expr(name, ts_type, "value", resolved, type_registry);
                    push_stmts.push_str(&format!("parts.push(\"{label}: \" + {val_expr});\n"));
                }

                Ok(ts_template! {
                    export function @{fn_name_ident}(value: @{interface_ident.clone()}): string {
                        const parts: string[] = [];
                        {$typescript TsStream::from_string(push_stmts)}
                        return "@{interface_name} { " + parts.join(", ") + " }";
                    }
                })
            }
        }
        Data::TypeAlias(type_alias) => {
            let type_name = input.name();
            let type_ident = ts_ident!(type_name);

            // Generate different output based on type body
            if type_alias.is_object() {
                // Object type: show fields
                let debug_fields: Vec<DebugField> = type_alias
                    .as_object()
                    .unwrap()
                    .iter()
                    .filter_map(|field| {
                        let opts = DebugFieldOptions::from_decorators(&field.decorators);
                        if opts.skip {
                            return None;
                        }
                        let label = opts.rename.unwrap_or_else(|| field.name.clone());
                        Some((label, field.name.clone(), field.ts_type.clone()))
                    })
                    .collect();

                let fn_name_ident = ts_ident!("{}ToString", type_name.to_case(Case::Camel));

                if debug_fields.is_empty() {
                    Ok(ts_template! {
                        export function @{fn_name_ident}(value: @{type_ident.clone()}): string {
                            return "@{type_name} {}";
                        }
                    })
                } else {
                    let mut push_stmts = String::new();
                    for (label, name, ts_type) in &debug_fields {
                        let resolved = resolved_fields.and_then(|rf| rf.get(name));
                        let val_expr =
                            debug_value_expr(name, ts_type, "value", resolved, type_registry);
                        push_stmts.push_str(&format!("parts.push(\"{label}: \" + {val_expr});\n"));
                    }

                    Ok(ts_template! {
                        export function @{fn_name_ident}(value: @{type_ident.clone()}): string {
                            const parts: string[] = [];
                            {$typescript TsStream::from_string(push_stmts)}
                            return "@{type_name} { " + parts.join(", ") + " }";
                        }
                    })
                }
            } else {
                // Union, intersection, tuple, or simple alias: use JSON.stringify
                let fn_name_ident = ts_ident!("{}ToString", type_name.to_case(Case::Camel));

                Ok(ts_template! {
                    export function @{fn_name_ident}(value: @{type_ident.clone()}): string {
                        return "@{type_name}(" + JSON.stringify(value) + ")";
                    }
                })
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::ts_syn::abi::{DecoratorIR, SpanIR};

    fn span() -> SpanIR {
        SpanIR::new(0, 0)
    }

    #[test]
    fn test_skip_flag() {
        let decorator = DecoratorIR {
            name: "Debug".into(),
            args_src: "skip".into(),
            span: span(),
            node: None,
        };

        let opts = DebugFieldOptions::from_decorators(&[decorator]);
        assert!(opts.skip, "skip flag should be true");
    }

    #[test]
    fn test_skip_false_keeps_field() {
        let decorator = DecoratorIR {
            name: "Debug".into(),
            args_src: r#"{ skip: false }"#.into(),
            span: span(),
            node: None,
        };

        let opts = DebugFieldOptions::from_decorators(&[decorator]);
        assert!(!opts.skip, "skip: false should not skip the field");
    }

    #[test]
    fn test_rename_option() {
        let decorator = DecoratorIR {
            name: "Debug".into(),
            args_src: r#"{ rename: "identifier" }"#.into(),
            span: span(),
            node: None,
        };

        let opts = DebugFieldOptions::from_decorators(&[decorator]);
        assert_eq!(opts.rename.as_deref(), Some("identifier"));
    }
}