// 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 `build_assign_from_flat`. AssignStmt flat encoding
// stores lhs/rhs expression edges split at `c.extra_int()` and the assignment
// operator in `c.aux()`. The cursor port must match legacy assign lowering
// without rehydrating lhs/rhs expression arrays.
module ssa

import v2.ast
import v2.token
import v2.types

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

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

fn assign_pin_stmt(lhs []ast.Expr, rhs []ast.Expr, op token.Token) ast.Stmt {
    return ast.Stmt(ast.AssignStmt{
        lhs: lhs
        rhs: rhs
        op:  op
    })
}

fn assign_pin_decl(name string, rhs ast.Expr) ast.Stmt {
    return assign_pin_stmt([assign_pin_ident(name)], [rhs], .decl_assign)
}

fn assign_pin_selector(lhs ast.Expr, rhs string) ast.Expr {
    return ast.Expr(ast.SelectorExpr{
        lhs: lhs
        rhs: ast.Ident{
            name: rhs
        }
    })
}

fn assign_pin_index(lhs ast.Expr, idx ast.Expr) ast.Expr {
    return ast.Expr(ast.IndexExpr{
        lhs:  lhs
        expr: idx
    })
}

fn assign_pin_prefix(op token.Token, expr ast.Expr) ast.Expr {
    return ast.Expr(ast.PrefixExpr{
        op:   op
        expr: expr
    })
}

fn assign_pin_fixed_array() ast.Expr {
    return ast.Expr(ast.ArrayInitExpr{
        exprs: [assign_pin_num('1'), assign_pin_num('2')]
        len:   ast.Expr(ast.PostfixExpr{
            op:   .not
            expr: ast.empty_expr
        })
    })
}

fn assign_pin_point_init() ast.Expr {
    return ast.Expr(ast.InitExpr{
        typ:    assign_pin_ident('Point')
        fields: [
            ast.FieldInit{
                name:  'x'
                value: assign_pin_num('1')
            },
        ]
    })
}

// Fixture: simple declarations, rebinding, compound ops, multi-assign, fixed
// array index stores, struct field stores, and pointer dereference stores.
fn make_assign_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:  assign_pin_ident('int')
                        },
                    ]
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'do_assign'
                    typ:   ast.FnType{}
                    stmts: [
                        assign_pin_decl('x', assign_pin_num('1')),
                        assign_pin_decl('y', assign_pin_ident('x')),
                        assign_pin_stmt([assign_pin_ident('x')], [
                            assign_pin_num('7')], .assign),
                        assign_pin_stmt([assign_pin_ident('x')], [
                            assign_pin_num('2')], .plus_assign),
                        assign_pin_stmt([assign_pin_ident('x'),
                            assign_pin_ident('y')], [assign_pin_ident('y'),
                            assign_pin_ident('x')], .assign),
                        assign_pin_decl('arr', assign_pin_fixed_array()),
                        assign_pin_stmt([
                            assign_pin_index(assign_pin_ident('arr'), assign_pin_num('0')),
                        ], [
                            assign_pin_ident('x'),
                        ], .assign),
                        assign_pin_decl('p', assign_pin_point_init()),
                        assign_pin_stmt([
                            assign_pin_selector(assign_pin_ident('p'), 'x'),
                        ], [
                            assign_pin_index(assign_pin_ident('arr'), assign_pin_num('0')),
                        ], .assign),
                        assign_pin_stmt([
                            assign_pin_selector(assign_pin_ident('p'), 'x'),
                        ], [
                            assign_pin_num('1'),
                        ], .plus_assign),
                        assign_pin_decl('ptr', assign_pin_prefix(.amp, assign_pin_ident('x'))),
                        assign_pin_stmt([
                            assign_pin_prefix(.mul, assign_pin_ident('ptr')),
                        ], [
                            assign_pin_selector(assign_pin_ident('p'), 'x'),
                        ], .assign),
                    ]
                }),
            ]
        },
    ]
}

fn build_via_legacy_assign(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_assign(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)
        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 test_build_assign_from_flat_matches_legacy() {
    files := make_assign_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_assign(files, env, 'assign_legacy')
    mod_flat := build_via_flat_assign(files, env, 'assign_flat')

    assert mod_legacy.funcs.len == mod_flat.funcs.len
    assert mod_legacy.funcs.len == 1
    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
}