// Copyright (c) 2026 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
// vtest build: macos
//
// Bit-equality pin for s172: `register_fn_signatures_from_flat` (flat-cursor
// port) must register the same fn signatures (fn_index, mod.funcs) as the
// legacy `register_fn_signatures`. The flat port walks one file's top-level
// stmts via FileCursor and only reads `.stmt_fn_decl` signatures via
// `Cursor.fn_decl_signature()` which returns FnDecl with `stmts = []`. Fn
// bodies are never decoded — the largest per-stmt savings of any SSA
// phase port.
module ssa

import v2.ast
import v2.types

fn make_fn_sigs_fixture() []ast.File {
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'main'
                }),
                ast.Stmt(ast.FnDecl{
                    name: 'add'
                    typ:  ast.FnType{
                        return_type: ast.Expr(ast.Ident{
                            name: 'int'
                        })
                        params:      [
                            ast.Parameter{
                                name: 'a'
                                typ:  ast.Expr(ast.Ident{
                                    name: 'int'
                                })
                            },
                            ast.Parameter{
                                name: 'b'
                                typ:  ast.Expr(ast.Ident{
                                    name: 'int'
                                })
                            },
                        ]
                    }
                }),
                ast.Stmt(ast.FnDecl{
                    name: 'noop'
                    typ:  ast.FnType{}
                }),
            ]
        },
    ]
}

// register_fn_signatures_from_flat on a file with no fns must not change
// fn_index or mod.funcs — same as register_fn_signatures.
fn test_register_fn_signatures_from_flat_no_fns_matches_legacy() {
    files := [
        ast.File{
            name:  'empty.v'
            mod:   'main'
            stmts: [ast.Stmt(ast.ModuleStmt{
                name: 'main'
            })]
        },
    ]
    flat := ast.flatten_files(files)

    env := types.Environment.new()

    mut mod_legacy := Module.new('fns_empty_legacy')
    mut b_legacy := Builder.new_with_env(mod_legacy, env)
    b_legacy.register_fn_signatures(files[0])

    mut mod_flat := Module.new('fns_empty_flat')
    mut b_flat := Builder.new_with_env(mod_flat, env)
    b_flat.register_fn_signatures_from_flat(flat.file_cursor(0))

    assert b_legacy.fn_index.len == b_flat.fn_index.len
    assert mod_legacy.funcs.len == mod_flat.funcs.len
}

// register_fn_signatures_from_flat on a file with two FnDecls (add + noop)
// must register both with identical fn_index entries and matching parameter
// counts on the SSA Function.
fn test_register_fn_signatures_from_flat_matches_legacy_for_two_fns() {
    files := make_fn_sigs_fixture()
    flat := ast.flatten_files(files)

    env := types.Environment.new()

    mut mod_legacy := Module.new('fns_two_legacy')
    mut b_legacy := Builder.new_with_env(mod_legacy, env)
    b_legacy.register_fn_signatures(files[0])

    mut mod_flat := Module.new('fns_two_flat')
    mut b_flat := Builder.new_with_env(mod_flat, env)
    b_flat.register_fn_signatures_from_flat(flat.file_cursor(0))

    // Both paths registered exactly 2 fns.
    assert b_legacy.fn_index.len == b_flat.fn_index.len
    assert b_legacy.fn_index.len == 2
    assert 'add' in b_legacy.fn_index
    assert 'add' in b_flat.fn_index
    assert 'noop' in b_legacy.fn_index
    assert 'noop' in b_flat.fn_index
    // Function ids match because identical registration order on isolated Modules.
    assert b_legacy.fn_index['add'] == b_flat.fn_index['add']
    assert b_legacy.fn_index['noop'] == b_flat.fn_index['noop']
    // mod.funcs slot counts match.
    assert mod_legacy.funcs.len == mod_flat.funcs.len
    // add has 2 params on both paths.
    add_legacy := mod_legacy.funcs[b_legacy.fn_index['add']]
    add_flat := mod_flat.funcs[b_flat.fn_index['add']]
    assert add_legacy.params.len == add_flat.params.len
    assert add_legacy.params.len == 2
    // noop has 0 params on both paths.
    noop_legacy := mod_legacy.funcs[b_legacy.fn_index['noop']]
    noop_flat := mod_flat.funcs[b_flat.fn_index['noop']]
    assert noop_legacy.params.len == noop_flat.params.len
    assert noop_legacy.params.len == 0
}