// 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 s182: `build_expr_stmt_from_flat` (seventh per-kind
// port inside the s175 seam) must dispatch the wrapped expr the same way
// the legacy `build_expr_stmt` does. The flat path walks UnsafeExpr's
// inner stmts via cursors (no `ast.Stmt` rehydration on that branch);
// non-unsafe / non-if exprs still decode via `decode_expr` since
// `build_expr` consumes legacy AST today.
module ssa

import v2.ast
import v2.types

// Two fixtures cover the two ports inside build_expr_stmt:
// - Plain expr (BasicLiteral) — exercises the fallback `build_expr` branch
// - UnsafeExpr containing a ReturnStmt — exercises the cursor-walk branch
//   that dispatches each inner stmt through `build_stmt_from_flat`.
fn make_expr_stmt_plain_fixture() []ast.File {
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'main'
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'do_expr'
                    typ:   ast.FnType{}
                    stmts: [
                        ast.Stmt(ast.ExprStmt{
                            expr: ast.Expr(ast.BasicLiteral{
                                kind:  .number
                                value: '42'
                            })
                        }),
                    ]
                }),
            ]
        },
    ]
}

fn make_expr_stmt_unsafe_fixture() []ast.File {
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'main'
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'do_unsafe'
                    typ:   ast.FnType{
                        return_type: ast.Expr(ast.Ident{
                            name: 'int'
                        })
                    }
                    stmts: [
                        ast.Stmt(ast.ExprStmt{
                            expr: ast.Expr(ast.UnsafeExpr{
                                stmts: [
                                    ast.Stmt(ast.ReturnStmt{
                                        exprs: [
                                            ast.Expr(ast.BasicLiteral{
                                                kind:  .number
                                                value: '11'
                                            }),
                                        ]
                                    }),
                                ]
                            })
                        }),
                    ]
                }),
            ]
        },
    ]
}

fn build_via_legacy_es(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_es(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))
    stmts := flat.file_cursor(0).stmts()
    for si in 0 .. stmts.len() {
        c := stmts.at(si)
        if c.kind() != .stmt_fn_decl {
            continue
        }
        decl := c.fn_decl_signature()
        fn_name := b.mangle_fn_name(decl)
        func_idx := b.fn_index[fn_name] or { continue }
        b.cur_func = func_idx
        b.label_blocks = map[string]BlockID{}
        entry := mod.add_block(func_idx, 'entry')
        b.cur_block = entry
        body := c.list_at(3)
        b.build_stmts_from_flat(body)
        if !b.block_has_terminator(b.cur_block) {
            mod.add_instr(.ret, b.cur_block, 0, []ValueID{})
        }
    }
    return mod
}

fn assert_same_es(mod_legacy &Module, mod_flat &Module) {
    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
}

fn test_build_expr_stmt_from_flat_plain_matches_legacy() {
    files := make_expr_stmt_plain_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_es(files, env, 'es_plain_legacy')
    mod_flat := build_via_flat_es(files, env, 'es_plain_flat')
    assert_same_es(mod_legacy, mod_flat)
}

fn test_build_expr_stmt_from_flat_unsafe_matches_legacy() {
    files := make_expr_stmt_unsafe_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_es(files, env, 'es_unsafe_legacy')
    mod_flat := build_via_flat_es(files, env, 'es_unsafe_flat')
    assert_same_es(mod_legacy, mod_flat)
}