// 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 the cursor-native rewrite of `build_fn_literal_from_flat`.
// The previous helper rehydrated the FnLiteral payload via three `decode_*`
// rounds — `decode_expr` on the FnType edge, `decode_expr` on every captured
// var edge, `decode_stmt` on every body-stmt edge — and dispatched to legacy
// `build_fn_literal`. The cursor-native rewrite walks the `.typ_fn` child for
// params + return_type, drops the captured-var rehydration entirely (legacy
// `build_fn_literal` never reads `captured_vars`), and routes body-stmt edges
// through `build_stmt_from_flat`. Pin asserts module-count parity for a
// fixture that constructs an anonymous fn with one int param and an int return.
module ssa

import v2.ast
import v2.types

fn fl_ident(name string) ast.Expr {
    return ast.Expr(ast.Ident{
        name: name
    })
}

fn fl_num(value string) ast.Expr {
    return ast.Expr(ast.BasicLiteral{
        kind:  .number
        value: value
    })
}

fn make_fn_literal_fixture() []ast.File {
    mut stmts := [
        ast.Stmt(ast.ModuleStmt{
            name: 'main'
        }),
    ]
    // fn use_anon() { f := fn (n int) int { return n } }
    stmts << ast.Stmt(ast.FnDecl{
        name:  'use_anon'
        typ:   ast.FnType{
            return_type: ast.empty_expr
        }
        stmts: [
            ast.Stmt(ast.AssignStmt{
                op:  .decl_assign
                lhs: [fl_ident('f')]
                rhs: [
                    ast.Expr(ast.FnLiteral{
                        typ:   ast.FnType{
                            params:      [
                                ast.Parameter{
                                    name: 'n'
                                    typ:  fl_ident('int')
                                },
                            ]
                            return_type: fl_ident('int')
                        }
                        stmts: [
                            ast.Stmt(ast.ReturnStmt{
                                exprs: [fl_ident('n')]
                            }),
                        ]
                    }),
                ]
            }),
        ]
    })
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: stmts
        },
    ]
}

fn build_via_legacy_fn_literal(files []ast.File, env &types.Environment, name string) &Module {
    mut mod := Module.new(name)
    mut b := Builder.new_with_env(mod, env)
    b.register_fn_signatures(files[0])
    b.build_fn_bodies(files[0])
    return mod
}

fn build_via_flat_fn_literal(files []ast.File, env &types.Environment, name string) &Module {
    flat := ast.flatten_files(files)
    mut mod := Module.new(name)
    mut b := Builder.new_with_env(mod, env)
    b.register_fn_signatures_from_flat(flat.file_cursor(0))
    b.build_fn_bodies_from_flat(flat.file_cursor(0))
    return mod
}

fn test_build_fn_literal_from_flat_matches_legacy() {
    files := make_fn_literal_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_fn_literal(files, env, 'fn_literal_legacy')
    mod_flat := build_via_flat_fn_literal(files, env, 'fn_literal_flat')

    assert mod_legacy.funcs.len == mod_flat.funcs.len
    assert mod_legacy.blocks.len == mod_flat.blocks.len
    assert mod_legacy.instrs.len == mod_flat.instrs.len
    assert mod_legacy.values.len == mod_flat.values.len
}