// 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 s194: `build_index_from_flat` is the tenth per-kind
// arm inside `build_expr_from_flat`. IndexExpr flat encoding (flat.v:1946)
// is (.expr_index, pos, -1, -1, 0, flags, [edge0=lhs, edge1=expr]). Both
// edges need full `decode_expr` rehydration: `build_index` recursively calls
// `build_expr` on both, and `expr_type(ast.Expr(expr))` for the pos.id
// type-check lookup. `is_gated` flag is intentionally ignored (build_index
// doesn't read it).
module ssa

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

// Fixture: `fn first(p &int) int { return p[0] }`. IndexExpr with
// lhs=Ident('p'), expr=BasicLiteral('0'). Param type is `&int` (ptr to int)
// so build_index falls through to the final ptr_t branch — emits GEP+load
// without needing struct registration for array/string/map.
fn make_index_fixture() []ast.File {
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'main'
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'first'
                    typ:   ast.FnType{
                        params:      [
                            ast.Parameter{
                                name: 'p'
                                typ:  ast.Expr(ast.PrefixExpr{
                                    op:   token.Token.amp
                                    expr: ast.Expr(ast.Ident{
                                        name: 'int'
                                    })
                                })
                            },
                        ]
                        return_type: ast.Expr(ast.Ident{
                            name: 'int'
                        })
                    }
                    stmts: [
                        ast.Stmt(ast.ReturnStmt{
                            exprs: [
                                ast.Expr(ast.IndexExpr{
                                    lhs:  ast.Expr(ast.Ident{
                                        name: 'p'
                                    })
                                    expr: ast.Expr(ast.BasicLiteral{
                                        kind:  .number
                                        value: '0'
                                    })
                                }),
                            ]
                        }),
                    ]
                }),
            ]
        },
    ]
}

fn build_via_legacy_index(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_index(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{}
        b.vars = map[string]ValueID{}
        entry := mod.add_block(func_idx, 'entry')
        b.cur_block = entry
        for param in decl.typ.params {
            param_type := b.ast_type_to_ssa(param.typ)
            param_val := mod.add_value_node(.argument, param_type, param.name, 0)
            mod.func_add_param(func_idx, param_val)
            alloca := mod.add_instr(.alloca, entry, mod.type_store.get_ptr(param_type), []ValueID{})
            mod.add_instr(.store, entry, 0, [param_val, alloca])
            b.vars[param.name] = alloca
        }
        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_index_from_flat_ptr_matches_legacy() {
    files := make_index_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_index(files, env, 'index_legacy')
    mod_flat := build_via_flat_index(files, env, 'index_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
}