// 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.
module ast

// Tests for `FlatBuilder.append_file_stmts`. The helper is the foundational
// primitive behind the transformer's upcoming `post_pass_to_flat` port —
// it appends pre-emitted stmt nodes to a registered file's stmt list and
// re-emits the file root, mirroring the post-pass mutation pattern used by
// `inject_embed_file_helper`, `inject_test_main`, and `generated_fns_parts`.

fn make_minimal_file_with_stmts(extra_stmts []Stmt) File {
    mut stmts := []Stmt{cap: 1 + extra_stmts.len}
    stmts << Stmt(ModuleStmt{
        name: 'foo'
    })
    for s in extra_stmts {
        stmts << s
    }
    return File{
        name:  'inline_minimal.v'
        mod:   'foo'
        stmts: stmts
    }
}

fn make_extra_stmt_a() Stmt {
    return Stmt(ConstDecl{
        fields: [
            FieldInit{
                name:  'A'
                value: Expr(BasicLiteral{
                    kind:  .number
                    value: '1'
                })
            },
        ]
    })
}

fn make_extra_stmt_b() Stmt {
    return Stmt(ConstDecl{
        fields: [
            FieldInit{
                name:  'B'
                value: Expr(BasicLiteral{
                    kind:  .number
                    value: '2'
                })
            },
        ]
    })
}

// Reference: build a file directly with both extras at construction time.
fn build_reference_with_extras() FlatAst {
    mut b := new_flat_builder()
    b.append_file(make_minimal_file_with_stmts([make_extra_stmt_a(),
        make_extra_stmt_b()]))
    return b.flat
}

// Subject: build the bare file, emit extras separately into the same builder,
// then splice them in via append_file_stmts.
fn build_subject_with_appended_extras() FlatAst {
    mut b := new_flat_builder()
    b.append_file(make_minimal_file_with_stmts([]))
    a_id := b.emit_stmt(make_extra_stmt_a())
    b_id := b.emit_stmt(make_extra_stmt_b())
    b.append_file_stmts(0, [a_id, b_id])
    return b.flat
}

fn test_append_file_stmts_signature_matches_reference() {
    ref_sig := build_reference_with_extras().signature()
    sub_sig := build_subject_with_appended_extras().signature()
    assert ref_sig == sub_sig
}

fn test_append_file_stmts_zero_extras_returns_existing_root() {
    mut b := new_flat_builder()
    original_id := b.append_file(make_minimal_file_with_stmts([]))
    returned_id := b.append_file_stmts(0, [])
    assert returned_id == original_id
}

fn test_append_file_stmts_invalid_idx_returns_invalid() {
    mut b := new_flat_builder()
    b.append_file(make_minimal_file_with_stmts([]))
    returned_id := b.append_file_stmts(-1, [FlatNodeId(0)])
    assert returned_id == invalid_flat_node_id
}