//! rust-langrpg — RPG IV free-format parser library
//!
//! Loads the BNF grammar embedded at compile time, builds a [`bnf::GrammarParser`],
//! and exposes helpers used by both the compiler binary and the demo binary.
//!
//! Also provides the typed AST ([`ast`]), BNF-to-AST lowering pass ([`lower`]),
//! and LLVM code-generator ([`codegen`]) used by the compiler pipeline.

pub mod ast;
pub mod lower;
pub mod codegen;

use bnf::{Grammar, Term};

/// The RPG IV BNF grammar, embedded at compile time from `src/rpg.bnf`.
const RPG_BNF: &str = include_str!("rpg.bnf");

// ─────────────────────────────────────────────────────────────────────────────
// Public API
// ─────────────────────────────────────────────────────────────────────────────

/// Load and validate the RPG IV grammar.
///
/// Returns `Err` if the BNF source is malformed.
pub fn load_grammar() -> Result<Grammar, bnf::Error> {
    RPG_BNF.parse::<Grammar>()
}

/// Parse `source` as the given `rule` (a non-terminal name such as `"statement"`).
///
/// Returns `Some(parse_tree_string)` for the first successful parse, or `None`
/// when the grammar cannot match the input.
pub fn parse_as<'a>(
    parser: &'a bnf::GrammarParser,
    source: &str,
    rule: &str,
) -> Option<String> {
    let target = Term::Nonterminal(rule.to_string());
    parser
        .parse_input_starting_with(source, &target)
        .next()
        .map(|tree| tree.to_string())
}

// ─────────────────────────────────────────────────────────────────────────────
// Demo helpers
// ─────────────────────────────────────────────────────────────────────────────

pub struct Example {
    pub label: &'static str,
    pub rule:  &'static str,
    pub src:   &'static str,
}

pub fn run_example(parser: &bnf::GrammarParser, ex: &Example) {
    println!("  ┌─ {} ({}) ─────────────────────", ex.label, ex.rule);
    println!("  │  source : {:?}", ex.src);
    match parse_as(parser, ex.src, ex.rule) {
        Some(tree) => {
            let preview: String = tree.lines().take(6).collect::<Vec<_>>().join("\n  │  ");
            println!("  │  result : OK");
            println!("  │  tree   : {}", preview);
        }
        None => println!("  │  result : NO PARSE"),
    }
    println!("  └──────────────────────────────────────────────");
    println!();
}

// ─────────────────────────────────────────────────────────────────────────────
// Unit tests
// ─────────────────────────────────────────────────────────────────────────────

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

    /// Leak a `Grammar` onto the heap so the returned `GrammarParser` can hold
    /// a `'static` reference to it.  The tiny allocation is intentional: this
    /// is test-only code and the process exits shortly after.
    fn make_parser() -> bnf::GrammarParser<'static> {
        let grammar: &'static bnf::Grammar =
            Box::leak(Box::new(load_grammar().expect("BNF must be valid")));
        grammar
            .build_parser()
            .expect("all non-terminals must resolve")
    }

    // ── Grammar loading ──────────────────────────────────────────────────────

    #[test]
    fn grammar_loads() {
        load_grammar().expect("grammar should parse without error");
    }

    #[test]
    fn parser_builds() {
        make_parser();
    }

    // ── Identifiers ──────────────────────────────────────────────────────────

    #[test]
    fn identifier_simple() {
        let p = make_parser();
        assert!(parse_as(&p, "abc", "identifier").is_some());
    }

    #[test]
    fn identifier_with_underscore() {
        let p = make_parser();
        assert!(parse_as(&p, "my_var", "identifier").is_some());
    }

    #[test]
    fn identifier_single_letter() {
        let p = make_parser();
        assert!(parse_as(&p, "x", "identifier").is_some());
    }

    // ── Literals ─────────────────────────────────────────────────────────────

    #[test]
    fn integer_literal() {
        let p = make_parser();
        assert!(parse_as(&p, "0", "integer-literal").is_some());
        assert!(parse_as(&p, "999", "integer-literal").is_some());
    }

    #[test]
    fn numeric_literal_decimal() {
        let p = make_parser();
        assert!(parse_as(&p, "3.14", "numeric-literal").is_some());
    }

    // ── Named constants ───────────────────────────────────────────────────────

    #[test]
    fn named_constants() {
        let p = make_parser();
        for s in &["*ON", "*OFF", "*BLANK", "*BLANKS", "*ZEROS", "*ZERO",
                   "*HIVAL", "*LOVAL", "*NULL"] {
            assert!(parse_as(&p, s, "named-constant").is_some(), "{} failed", s);
        }
    }

    // ── Type specs ────────────────────────────────────────────────────────────

    #[test]
    fn type_spec_char() {
        let p = make_parser();
        assert!(parse_as(&p, "CHAR(50)", "type-spec").is_some());
    }

    #[test]
    fn type_spec_packed() {
        let p = make_parser();
        assert!(parse_as(&p, "PACKED(9:2)", "type-spec").is_some());
    }

    #[test]
    fn type_spec_date() {
        let p = make_parser();
        assert!(parse_as(&p, "DATE", "type-spec").is_some());
    }

    #[test]
    fn type_spec_ind() {
        let p = make_parser();
        assert!(parse_as(&p, "IND", "type-spec").is_some());
    }

    #[test]
    fn type_spec_pointer() {
        let p = make_parser();
        assert!(parse_as(&p, "POINTER", "type-spec").is_some());
    }

    // ── Declarations ─────────────────────────────────────────────────────────

    #[test]
    fn standalone_decl_no_inz() {
        let p = make_parser();
        assert!(parse_as(&p, "DCL-S total PACKED(9:2);", "standalone-decl").is_some());
    }

    #[test]
    fn standalone_decl_with_inz() {
        let p = make_parser();
        assert!(parse_as(&p, "DCL-S counter INT(10) INZ(0);", "standalone-decl").is_some());
    }

    #[test]
    fn constant_decl() {
        let p = make_parser();
        assert!(parse_as(&p, "DCL-C MAX CONST(100);", "constant-decl").is_some());
    }

    // ── Control spec ──────────────────────────────────────────────────────────

    #[test]
    fn ctl_opt_nomain() {
        let p = make_parser();
        assert!(parse_as(&p, "CTL-OPT NOMAIN;", "control-spec").is_some());
    }

    #[test]
    fn ctl_opt_dftactgrp_no() {
        let p = make_parser();
        assert!(parse_as(&p, "CTL-OPT DFTACTGRP(*NO);", "control-spec").is_some());
    }

    // ── Statements ───────────────────────────────────────────────────────────

    #[test]
    fn assign_simple() {
        let p = make_parser();
        assert!(parse_as(&p, "x=1;", "assign-stmt").is_some());
    }

    #[test]
    fn return_with_expr() {
        let p = make_parser();
        assert!(parse_as(&p, "RETURN result;", "return-stmt").is_some());
    }

    #[test]
    fn return_bare() {
        let p = make_parser();
        assert!(parse_as(&p, "RETURN;", "return-stmt").is_some());
    }

    #[test]
    fn leave_stmt() {
        let p = make_parser();
        assert!(parse_as(&p, "LEAVE;", "leave-stmt").is_some());
    }

    #[test]
    fn iter_stmt() {
        let p = make_parser();
        assert!(parse_as(&p, "ITER;", "iter-stmt").is_some());
    }

    #[test]
    fn exsr_stmt() {
        let p = make_parser();
        assert!(parse_as(&p, "EXSR myRoutine;", "exsr-stmt").is_some());
    }

    #[test]
    fn read_stmt() {
        let p = make_parser();
        assert!(parse_as(&p, "READ myFile;", "read-stmt").is_some());
    }

    #[test]
    fn write_stmt() {
        let p = make_parser();
        assert!(parse_as(&p, "WRITE outRec;", "write-stmt").is_some());
    }

    #[test]
    fn chain_stmt() {
        let p = make_parser();
        assert!(parse_as(&p, "CHAIN key myFile;", "chain-stmt").is_some());
    }

    #[test]
    fn setll_start() {
        let p = make_parser();
        assert!(parse_as(&p, "SETLL *START myFile;", "setll-stmt").is_some());
    }

    #[test]
    fn open_close() {
        let p = make_parser();
        assert!(parse_as(&p, "OPEN myFile;", "open-stmt").is_some());
        assert!(parse_as(&p, "CLOSE myFile;", "close-stmt").is_some());
    }

    #[test]
    fn close_all() {
        let p = make_parser();
        assert!(parse_as(&p, "CLOSE *ALL;", "close-stmt").is_some());
    }

    // ── Expressions ──────────────────────────────────────────────────────────

    #[test]
    fn expression_addition() {
        let p = make_parser();
        assert!(parse_as(&p, "a+b", "expression").is_some());
    }

    #[test]
    fn expression_comparison() {
        let p = make_parser();
        assert!(parse_as(&p, "x=1", "expression").is_some());
        assert!(parse_as(&p, "x<>0", "expression").is_some());
    }

    #[test]
    fn expression_not() {
        let p = make_parser();
        assert!(parse_as(&p, "NOT flag", "expression").is_some());
    }

    #[test]
    fn expression_parenthesised() {
        let p = make_parser();
        assert!(parse_as(&p, "(x+1)", "expression").is_some());
    }

    // ── Built-in functions ───────────────────────────────────────────────────

    #[test]
    fn builtin_len() {
        let p = make_parser();
        assert!(parse_as(&p, "%LEN(myField)", "built-in-function").is_some());
    }

    #[test]
    fn builtin_trim() {
        let p = make_parser();
        assert!(parse_as(&p, "%TRIM(s)", "built-in-function").is_some());
    }

    #[test]
    fn builtin_eof_no_arg() {
        let p = make_parser();
        assert!(parse_as(&p, "%EOF()", "built-in-function").is_some());
    }

    #[test]
    fn builtin_subst_3arg() {
        let p = make_parser();
        assert!(parse_as(&p, "%SUBST(s:1:5)", "built-in-function").is_some());
    }

    // ── Date / time formats ──────────────────────────────────────────────────

    #[test]
    fn date_formats() {
        let p = make_parser();
        for fmt in &["*MDY", "*DMY", "*YMD", "*JUL", "*ISO", "*USA", "*EUR", "*JIS"] {
            assert!(parse_as(&p, fmt, "date-format").is_some(), "{} failed", fmt);
        }
    }

    #[test]
    fn time_formats() {
        let p = make_parser();
        for fmt in &["*HMS", "*ISO", "*USA", "*EUR", "*JIS"] {
            assert!(parse_as(&p, fmt, "time-format").is_some(), "{} failed", fmt);
        }
    }

    // ── Qualified names ───────────────────────────────────────────────────────

    #[test]
    fn qualified_name_simple() {
        let p = make_parser();
        assert!(parse_as(&p, "myVar", "qualified-name").is_some());
    }

    #[test]
    fn qualified_name_dotted() {
        let p = make_parser();
        assert!(parse_as(&p, "ds.field", "qualified-name").is_some());
    }

    // ── Duration codes ───────────────────────────────────────────────────────

    #[test]
    fn duration_codes() {
        let p = make_parser();
        for code in &["*YEARS", "*MONTHS", "*DAYS", "*HOURS", "*MINUTES",
                      "*SECONDS", "*MSECONDS"] {
            assert!(parse_as(&p, code, "duration-code").is_some(), "{} failed", code);
        }
    }

    // ── Hello World program ───────────────────────────────────────────────────

    /// The Hello World source from the README, embedded at compile time so the
    /// test works regardless of the working directory.
    const HELLO_RPG: &str = include_str!("../hello.rpg");

    /// Verify that the full hello.rpg program parses against the top-level
    /// `<program>` grammar rule.
    #[test]
    fn hello_rpg_parses() {
        let p = make_parser();
        let tree = parse_as(&p, HELLO_RPG.trim(), "program");
        assert!(
            tree.is_some(),
            "hello.rpg did not match the <program> rule\n\nsource:\n{}",
            HELLO_RPG,
        );
    }


}