// 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 s185: `build_fn_from_flat` (the s185 wiring step)
// must build the same SSA bodies as the legacy `build_fn`. This is the
// first session where `build_fn_bodies_from_flat` no longer decodes the
// FnDecl body — instead `Cursor.fn_decl_signature()` returns a body-less
// FnDecl, and `build_fn_from_flat` walks the body stmts directly via
// `c.list_at(3)` cursors. Pin covers plain fn / fn with params / extern
// (body_len==0) / multi-body fn branches.
module ssa

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

// Fixture exercises every branch of the new build_fn_from_flat:
// - `answer`: plain fn returning a literal (single-stmt body)
// - `add`: fn with two params + decl_assign + return (param setup + body)
// - `noop`: extern-style fn with no body (body_len==0 branch)
// - `loop_break`: fn with a for-loop containing break (heavyweight stmt arms)
fn make_build_fn_from_flat_fixture() []ast.File {
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'main'
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'answer'
                    typ:   ast.FnType{
                        return_type: ast.Expr(ast.Ident{
                            name: 'int'
                        })
                    }
                    stmts: [
                        ast.Stmt(ast.ReturnStmt{
                            exprs: [
                                ast.Expr(ast.BasicLiteral{
                                    kind:  .number
                                    value: '42'
                                }),
                            ]
                        }),
                    ]
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'add'
                    typ:   ast.FnType{
                        params:      [
                            ast.Parameter{
                                name: 'a'
                                typ:  ast.Expr(ast.Ident{
                                    name: 'int'
                                })
                            },
                            ast.Parameter{
                                name: 'b'
                                typ:  ast.Expr(ast.Ident{
                                    name: 'int'
                                })
                            },
                        ]
                        return_type: ast.Expr(ast.Ident{
                            name: 'int'
                        })
                    }
                    stmts: [
                        ast.Stmt(ast.AssignStmt{
                            lhs: [
                                ast.Expr(ast.Ident{
                                    name: 'c'
                                }),
                            ]
                            rhs: [
                                ast.Expr(ast.BasicLiteral{
                                    kind:  .number
                                    value: '0'
                                }),
                            ]
                            op:  token.Token.decl_assign
                        }),
                        ast.Stmt(ast.ReturnStmt{
                            exprs: [
                                ast.Expr(ast.Ident{
                                    name: 'c'
                                }),
                            ]
                        }),
                    ]
                }),
                ast.Stmt(ast.FnDecl{
                    name: 'noop'
                    typ:  ast.FnType{}
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'loop_break'
                    typ:   ast.FnType{}
                    stmts: [
                        ast.Stmt(ast.ForStmt{
                            stmts: [
                                ast.Stmt(ast.FlowControlStmt{
                                    op: token.Token.key_break
                                }),
                            ]
                        }),
                    ]
                }),
            ]
        },
    ]
}

fn build_via_legacy_fn_bodies(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_bodies(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_from_flat_matches_legacy() {
    files := make_build_fn_from_flat_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_fn_bodies(files, env, 'bf_legacy')
    mod_flat := build_via_flat_fn_bodies(files, env, 'bf_flat')

    assert mod_legacy.funcs.len == mod_flat.funcs.len
    assert mod_legacy.funcs.len == 4
    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
}