// 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 s197: `build_init_from_flat` is the thirteenth
// per-kind arm inside `build_expr_from_flat`. InitExpr flat encoding
// (flat.v:1962) is (.expr_init, pos, -1, -1, 0, 0,
// [edge0=typ, edge1..n=aux_field_init]). The cursor port decodes the type and
// every field value via `decode_expr` (unavoidable: build_init_expr resolves
// the type through ast_type_to_ssa and recursively builds FieldInit.value),
// then constructs ast.InitExpr{typ, fields, pos} and dispatches to existing
// build_init_expr.
module ssa

import v2.ast
import v2.types

// Fixture: `struct Point { x int y int } fn make_point() Point {
// return Point{x: 1, y: 2} }`. Exercises named struct-literal field init in
// declaration order without needing array/map literal lowering.
fn make_init_fixture() []ast.File {
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'main'
                }),
                ast.Stmt(ast.StructDecl{
                    name:   'Point'
                    fields: [
                        ast.FieldDecl{
                            name: 'x'
                            typ:  ast.Expr(ast.Ident{
                                name: 'int'
                            })
                        },
                        ast.FieldDecl{
                            name: 'y'
                            typ:  ast.Expr(ast.Ident{
                                name: 'int'
                            })
                        },
                    ]
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'make_point'
                    typ:   ast.FnType{
                        return_type: ast.Expr(ast.Ident{
                            name: 'Point'
                        })
                    }
                    stmts: [
                        ast.Stmt(ast.ReturnStmt{
                            exprs: [
                                ast.Expr(ast.InitExpr{
                                    typ:    ast.Expr(ast.Ident{
                                        name: 'Point'
                                    })
                                    fields: [
                                        ast.FieldInit{
                                            name:  'x'
                                            value: ast.Expr(ast.BasicLiteral{
                                                kind:  .number
                                                value: '1'
                                            })
                                        },
                                        ast.FieldInit{
                                            name:  'y'
                                            value: ast.Expr(ast.BasicLiteral{
                                                kind:  .number
                                                value: '2'
                                            })
                                        },
                                    ]
                                }),
                            ]
                        }),
                    ]
                }),
            ]
        },
    ]
}

fn build_via_legacy_init(files []ast.File, env &types.Environment, name string) &Module {
    mut mod := Module.new(name)
    mut b := Builder.new_with_env(mod, env)
    b.register_types_pass1(files[0])
    b.register_types_pass2(files[0])
    b.register_fn_signatures(files[0])
    b.build_fn_bodies(files[0])
    return mod
}

fn build_via_flat_init(files []ast.File, env &types.Environment, name string) &Module {
    flat := ast.flatten_files(files)
    fc := flat.file_cursor(0)
    mut mod := Module.new(name)
    mut b := Builder.new_with_env(mod, env)
    b.register_types_pass1_from_flat(fc)
    b.register_types_pass2_from_flat(fc)
    b.register_fn_signatures_from_flat(fc)
    stmts := fc.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{}
        b.vars = map[string]ValueID{}
        entry := mod.add_block(func_idx, 'entry')
        b.cur_block = entry
        body := c.list_at(3)
        for bi in 0 .. body.len() {
            stmt_c := body.at(bi)
            if stmt_c.kind() == .stmt_return {
                ret_expr_c := stmt_c.edge(0)
                val := b.build_expr_from_flat(ret_expr_c)
                mod.add_instr(.ret, b.cur_block, 0, [val])
            } else {
                b.build_stmt_from_flat(stmt_c)
            }
        }
        if !b.block_has_terminator(b.cur_block) {
            mod.add_instr(.ret, b.cur_block, 0, []ValueID{})
        }
    }
    return mod
}

fn test_build_init_from_flat_matches_legacy() {
    files := make_init_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_init(files, env, 'init_legacy')
    mod_flat := build_via_flat_init(files, env, 'init_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
}