//! `charka-codegen` — emisión de Rust desde el IR del transpilador.
//!
//! Etapa final del pipeline COBOL→Rust: toma el [`Ir`] de `charka-ir`
//! y produce un fuente Rust (un `String`) que, compilado contra
//! `charka-runtime`, ejecuta la lógica del programa COBOL original.
//!
//! La forma del código emitido:
//!
//! - Un `struct Program` con un campo por cada dato elemental — `Num`
//!   para los numéricos, `Text` para los alfanuméricos.
//! - `Program::new()` inicializa los campos desde sus cláusulas `VALUE`.
//! - Un método `p_<párrafo>(&mut self)` por cada párrafo del PROCEDURE.
//! - `run()` los encadena en orden (el «caer» de COBOL); `main()`
//!   construye el `Program` y lo corre.
//!
//! Es **tolerante**: lo que no sabe transpilar (un `Stmt::Unknown`, un
//! dato sin resolver, `**`) se emite como un comentario `// charka:` —
//! el código generado siempre compila.
//!
//! Alcance v1 — fuera: grupos como campo propio, `REDEFINES`,
//! `OCCURS`/tablas, `PERFORM ... THRU` como rango, E/S de ficheros,
//! `EVALUATE`, CICS y SQL embebido.

#![forbid(unsafe_code)]

mod emit;
mod expr;
mod stmt;
mod sym;

use std::collections::HashMap;

use charka_ir::{Ir, Procedure};

use emit::Emitter;
use expr::rust_str;
use stmt::emit_stmt;
use sym::{paragraph_method, Field, FieldKind, Symbols};

/// Transpila un [`Ir`] a un fuente Rust completo (un `main.rs`).
pub fn generate(ir: &Ir) -> String {
    let sym = Symbols::build(&ir.model);
    let mut em = Emitter::new();
    emit_header(&mut em);
    emit_struct(&mut em, &sym);
    emit_impl(&mut em, &sym, ir);
    emit_main(&mut em);
    em.finish()
}

/// El preámbulo: doc, `allow`s, el `use` del runtime y el helper `dec`.
fn emit_header(em: &mut Emitter) {
    em.line("//! Generado por charka — transpilador COBOL → Rust.");
    em.line("//! No editar a mano: regenerar desde el fuente COBOL.");
    em.blank();
    em.line(
        "#![allow(dead_code, unused_mut, unused_variables, unused_parens, \
unreachable_code, clippy::all)]",
    );
    em.blank();
    em.line("use charka_runtime::*;");
    em.blank();
    em.line("/// Construye un `Decimal` desde un literal numérico COBOL.");
    em.line("fn dec(s: &str) -> Decimal {");
    em.line("    Decimal::parse(s).expect(\"charka: literal numérico inválido\")");
    em.line("}");
    em.blank();
}

/// El `struct Program` con un campo por dato elemental.
fn emit_struct(em: &mut Emitter, sym: &Symbols) {
    em.line("/// El estado del programa: un campo por cada dato elemental.");
    em.line("struct Program {");
    em.indent();
    for f in &sym.fields {
        let elem = match f.kind {
            FieldKind::Num { .. } => "Num",
            FieldKind::Text { .. } => "Text",
        };
        let ty = match f.occurs {
            None => elem.to_string(),
            Some(_) => format!("Vec<{elem}>"),
        };
        em.line(&format!("{}: {ty},", f.ident));
    }
    em.dedent();
    em.line("}");
    em.blank();
}

/// El bloque `impl Program`: `new`, los párrafos y `run`.
fn emit_impl(em: &mut Emitter, sym: &Symbols, ir: &Ir) {
    em.line("impl Program {");
    em.indent();

    // new()
    em.line("fn new() -> Self {");
    em.indent();
    em.line("Self {");
    em.indent();
    for f in &sym.fields {
        em.line(&format!("{}: {},", f.ident, field_init(f)));
    }
    em.dedent();
    em.line("}");
    em.dedent();
    em.line("}");
    em.blank();

    // Un método por párrafo.
    let methods = paragraph_methods(ir);
    for (name, proc) in &methods {
        em.line(&format!("fn {name}(&mut self) {{"));
        em.indent();
        for s in &proc.body {
            emit_stmt(em, sym, s);
        }
        em.dedent();
        em.line("}");
        em.blank();
    }

    // run() — encadena los párrafos en orden.
    em.line("fn run(&mut self) {");
    em.indent();
    if methods.is_empty() {
        em.line("// programa sin PROCEDURE division");
    }
    for (name, _) in &methods {
        em.line(&format!("self.{name}();"));
    }
    em.dedent();
    em.line("}");

    em.dedent();
    em.line("}");
    em.blank();
}

/// El `fn main`.
fn emit_main(em: &mut Emitter) {
    em.line("fn main() {");
    em.indent();
    em.line("Program::new().run();");
    em.dedent();
    em.line("}");
}

/// El inicializador de un campo, a partir de su `VALUE` ya
/// normalizado por `charka-ir`. Una tabla (`OCCURS n`) se inicializa
/// como un `Vec` de `n` copias del valor inicial.
fn field_init(f: &Field) -> String {
    let scalar = match &f.kind {
        FieldKind::Num { int, frac, signed } => format!(
            "Num::with_value(Picture::new({int}, {frac}, {signed}), {})",
            rust_str(&f.init)
        ),
        FieldKind::Text { len } => {
            format!("Text::with_value({len}, {})", rust_str(&f.init))
        }
    };
    match f.occurs {
        None => scalar,
        Some(n) => format!("vec![{scalar}; {n}]"),
    }
}

/// Asigna a cada párrafo un nombre de método único.
fn paragraph_methods(ir: &Ir) -> Vec<(String, &Procedure)> {
    let mut seen: HashMap<String, u32> = HashMap::new();
    let mut out = Vec::new();
    for proc in &ir.procedures {
        let base = paragraph_method(&proc.name);
        let n = seen.entry(base.clone()).or_insert(0);
        let name = if *n > 0 { format!("{base}_{n}") } else { base };
        *n += 1;
        out.push((name, proc));
    }
    out
}

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

    /// Helper: lexa, parsea, baja a IR y transpila un fuente COBOL.
    fn gen(src: &str) -> String {
        let toks = charka_lexer::lex(src, charka_lexer::SourceFormat::Free).expect("lex");
        let prog = charka_parser::parse(&toks).expect("parse");
        let ir = charka_ir::lower(&prog);
        generate(&ir)
    }

    /// Un programa COBOL de demostración, razonablemente completo.
    const DEMO: &str = "IDENTIFICATION DIVISION.\n\
         PROGRAM-ID. DEMO.\n\
         DATA DIVISION.\n\
         WORKING-STORAGE SECTION.\n\
         01 WS-A    PIC 9(3) VALUE 10.\n\
         01 WS-B    PIC 9(3).\n\
         01 WS-NAME PIC X(8) VALUE 'BOB'.\n\
         PROCEDURE DIVISION.\n\
         MAIN-PARA.\n\
             MOVE 5 TO WS-B.\n\
             COMPUTE WS-B = WS-A + WS-B.\n\
             DISPLAY 'B=' WS-B.\n\
             IF WS-B > 0 DISPLAY 'POS' END-IF.\n\
             PERFORM SUB-PARA.\n\
             STOP RUN.\n\
         SUB-PARA.\n\
             DISPLAY WS-NAME.\n";

    #[test]
    fn header_and_main_are_emitted() {
        let out = gen(DEMO);
        assert!(out.contains("use charka_runtime::*;"));
        assert!(out.contains("fn dec(s: &str) -> Decimal {"));
        assert!(out.contains("fn main() {"));
        assert!(out.contains("Program::new().run();"));
    }

    #[test]
    fn numeric_field_becomes_num() {
        let out = gen(DEMO);
        assert!(out.contains("ws_a: Num,"));
        assert!(out.contains("Num::with_value(Picture::new(3, 0, false), \"10\")"));
    }

    #[test]
    fn alphanumeric_field_becomes_text() {
        let out = gen(DEMO);
        assert!(out.contains("ws_name: Text,"));
        assert!(out.contains("Text::with_value(8, \"BOB\")"));
    }

    #[test]
    fn move_emits_a_store() {
        assert!(gen(DEMO).contains("self.ws_b.store(dec(\"5\"));"));
    }

    #[test]
    fn compute_emits_the_expression() {
        let out = gen(DEMO);
        assert!(out.contains("self.ws_b.store((self.ws_a.value()).add(&(self.ws_b.value())));"));
    }

    #[test]
    fn display_emits_a_println() {
        let out = gen(DEMO);
        assert!(out.contains("println!(\"{}{}\", \"B=\", self.ws_b.display());"));
    }

    #[test]
    fn if_emits_a_rust_if() {
        let out = gen(DEMO);
        assert!(out.contains("if (self.ws_b.value()) > (dec(\"0\")) {"));
    }

    #[test]
    fn paragraphs_become_methods_and_run_chains_them() {
        let out = gen(DEMO);
        assert!(out.contains("fn p_main_para(&mut self) {"));
        assert!(out.contains("fn p_sub_para(&mut self) {"));
        assert!(out.contains("fn run(&mut self) {"));
        assert!(out.contains("self.p_main_para();"));
        assert!(out.contains("self.p_sub_para();"));
    }

    #[test]
    fn perform_calls_the_paragraph_method() {
        assert!(gen(DEMO).contains("self.p_sub_para();"));
    }

    #[test]
    fn stop_run_exits() {
        assert!(gen(DEMO).contains("std::process::exit(0);"));
    }

    #[test]
    fn unknown_verb_becomes_a_comment() {
        let out = gen("PROCEDURE DIVISION.\n\
             MAIN.\n\
                 INITIALIZE WS-X.\n");
        assert!(out.contains("// charka: verbo no transpilado — INITIALIZE"));
    }

    #[test]
    fn add_giving_emits_a_sum() {
        let out = gen("DATA DIVISION.\n\
             WORKING-STORAGE SECTION.\n\
             01 A PIC 9(3).\n\
             01 B PIC 9(3).\n\
             01 C PIC 9(3).\n\
             PROCEDURE DIVISION.\n\
             MAIN.\n\
                 ADD A B GIVING C.\n");
        assert!(out.contains("self.c.store((self.a.value()).add(&(self.b.value())));"));
    }

    #[test]
    fn perform_times_emits_a_loop() {
        let out = gen("PROCEDURE DIVISION.\n\
             MAIN.\n\
                 PERFORM SUB 3 TIMES.\n\
             SUB.\n\
                 CONTINUE.\n");
        assert!(out.contains("for _ in 0..3usize {"));
    }

    #[test]
    fn perform_varying_emits_init_loop_and_increment() {
        let out = gen("DATA DIVISION.\n\
             WORKING-STORAGE SECTION.\n\
             01 WS-I PIC 9(2).\n\
             01 WS-N PIC 9(3).\n\
             PROCEDURE DIVISION.\n\
             MAIN.\n\
                 PERFORM VARYING WS-I FROM 1 BY 1 UNTIL WS-I > 5\n\
                     ADD 1 TO WS-N\n\
                 END-PERFORM.\n");
        assert!(out.contains("self.ws_i.store(dec(\"1\"));"));
        assert!(out.contains("while !((self.ws_i.value()) > (dec(\"5\"))) {"));
        assert!(out.contains("self.ws_i.store(self.ws_i.value().add(&(dec(\"1\"))));"));
    }

    #[test]
    fn evaluate_emits_an_if_else_chain() {
        let out = gen("DATA DIVISION.\n\
             WORKING-STORAGE SECTION.\n\
             01 WS-X PIC 9(1).\n\
             PROCEDURE DIVISION.\n\
             MAIN.\n\
                 EVALUATE WS-X\n\
                     WHEN 1 DISPLAY 'UNO'\n\
                     WHEN OTHER DISPLAY 'OTRO'\n\
                 END-EVALUATE.\n");
        assert!(out.contains("if ((self.ws_x.value()) == (dec(\"1\"))) {"));
        assert!(out.contains("} else {"));
    }

    #[test]
    fn level_88_condition_resolves_to_a_comparison() {
        let out = gen("DATA DIVISION.\n\
             WORKING-STORAGE SECTION.\n\
             01 WS-FLAG PIC X VALUE 'N'.\n\
                88 ES-SI VALUE 'Y'.\n\
             PROCEDURE DIVISION.\n\
             MAIN.\n\
                 IF ES-SI DISPLAY 'SI' END-IF.\n");
        // ES-SI equivale a `WS-FLAG = 'Y'` (comparación de texto).
        assert!(out.contains("cobol_text_cmp(self.ws_flag.display().as_str(), \"Y\").is_eq()"));
    }

    #[test]
    fn occurs_emits_a_vec_field_and_indexed_access() {
        let out = gen("DATA DIVISION.\n\
             WORKING-STORAGE SECTION.\n\
             01 WS-T.\n\
                05 WS-E PIC 9(3) OCCURS 4 TIMES.\n\
             01 WS-I PIC 9(1).\n\
             PROCEDURE DIVISION.\n\
             MAIN.\n\
                 MOVE 7 TO WS-E(WS-I).\n");
        assert!(out.contains("ws_e: Vec<Num>,"));
        assert!(out.contains("; 4]"));
        assert!(out.contains("self.ws_e["));
        assert!(out.contains(".saturating_sub(1)]"));
    }

    #[test]
    fn string_concatenates_and_unstring_splits() {
        let out = gen("DATA DIVISION.\n\
             WORKING-STORAGE SECTION.\n\
             01 WS-A PIC X(4).\n\
             01 WS-B PIC X(4).\n\
             01 WS-OUT PIC X(10).\n\
             01 WS-SRC PIC X(10).\n\
             PROCEDURE DIVISION.\n\
             MAIN.\n\
                 STRING WS-A WS-B DELIMITED BY SIZE INTO WS-OUT END-STRING.\n\
                 UNSTRING WS-SRC DELIMITED BY ',' INTO WS-A WS-B END-UNSTRING.\n");
        assert!(out.contains("self.ws_out.store(&format!("));
        assert!(out.contains("__src.split(__delim.as_str())"));
        assert!(out.contains("__it.next().unwrap_or(\"\")"));
    }

    #[test]
    fn inspect_emits_tally_and_replace() {
        let out = gen("DATA DIVISION.\n\
             WORKING-STORAGE SECTION.\n\
             01 WS-T PIC X(10).\n\
             01 WS-N PIC 9(3).\n\
             PROCEDURE DIVISION.\n\
             MAIN.\n\
                 INSPECT WS-T TALLYING WS-N FOR ALL 'X'.\n\
                 INSPECT WS-T REPLACING ALL 'X' BY 'Y'.\n");
        assert!(out.contains(".matches("));
        assert!(out.contains("Decimal::from_integer(__n)"));
        assert!(out.contains(".replace("));
    }

    #[test]
    fn empty_program_still_compiles_shape() {
        let out = gen("");
        assert!(out.contains("struct Program {"));
        assert!(out.contains("fn main() {"));
        assert!(out.contains("fn run(&mut self) {"));
    }
}