// 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 s196: `build_call_from_flat` is the twelfth per-kind
// arm inside `build_expr_from_flat`. CallExpr flat encoding (flat.v:1862) is
// (.expr_call, pos, -1, -1, 0, 0, [edge0=lhs, edge1..n=args]). The cursor
// port decodes the lhs and every arg via `decode_expr` (unavoidable:
// build_call pattern-matches heavily on `expr.lhs is ast.SelectorExpr`,
// `expr.lhs is ast.Ident`, and `arg is ast.ModifierExpr`), then constructs
// ast.CallExpr{lhs, args, pos} and dispatches to existing build_call.
module ssa

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

// Fixture: `fn add(x int, y int) int { return x + y } fn main() { add(1, 2) }`.
// The main body contains an ExprStmt wrapping a CallExpr with lhs=Ident('add')
// and args=[BasicLiteral('1'), BasicLiteral('2')]. Exercises the common-case
// free-function call path (no struct/method/builtin resolution).
fn make_call_fixture() []ast.File {
    return [
        ast.File{
            name:  'main.v'
            mod:   'main'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'main'
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'add'
                    typ:   ast.FnType{
                        params:      [
                            ast.Parameter{
                                name: 'x'
                                typ:  ast.Expr(ast.Ident{
                                    name: 'int'
                                })
                            },
                            ast.Parameter{
                                name: 'y'
                                typ:  ast.Expr(ast.Ident{
                                    name: 'int'
                                })
                            },
                        ]
                        return_type: ast.Expr(ast.Ident{
                            name: 'int'
                        })
                    }
                    stmts: [
                        ast.Stmt(ast.ReturnStmt{
                            exprs: [
                                ast.Expr(ast.InfixExpr{
                                    op:  token.Token.plus
                                    lhs: ast.Expr(ast.Ident{
                                        name: 'x'
                                    })
                                    rhs: ast.Expr(ast.Ident{
                                        name: 'y'
                                    })
                                }),
                            ]
                        }),
                    ]
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'main'
                    typ:   ast.FnType{
                        return_type: ast.empty_expr
                    }
                    stmts: [
                        ast.Stmt(ast.ExprStmt{
                            expr: ast.Expr(ast.CallExpr{
                                lhs:  ast.Expr(ast.Ident{
                                    name: 'add'
                                })
                                args: [
                                    ast.Expr(ast.BasicLiteral{
                                        kind:  .number
                                        value: '1'
                                    }),
                                    ast.Expr(ast.BasicLiteral{
                                        kind:  .number
                                        value: '2'
                                    }),
                                ]
                            })
                        }),
                    ]
                }),
            ]
        },
    ]
}

fn build_via_legacy_call(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_call(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 if stmt_c.kind() == .stmt_expr {
                expr_c := stmt_c.edge(0)
                b.build_expr_from_flat(expr_c)
            } else {
                b.build_stmt_from_flat(stmt_c)
            }
        }
        if !b.block_has_terminator(b.cur_block) {
            if fn_name == 'main' {
                zero := mod.get_or_add_const(mod.type_store.get_int(32), '0')
                mod.add_instr(.ret, b.cur_block, 0, [zero])
            } else {
                mod.add_instr(.ret, b.cur_block, 0, []ValueID{})
            }
        }
    }
    return mod
}

fn test_build_call_from_flat_matches_legacy() {
    _ = token.Token.plus
    files := make_call_fixture()
    env := types.Environment.new()
    mod_legacy := build_via_legacy_call(files, env, 'call_legacy')
    mod_flat := build_via_flat_call(files, env, 'call_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
}

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

fn call_test_param(name string, typ ast.Expr) ast.Parameter {
    return ast.Parameter{
        name: name
        typ:  typ
    }
}

fn make_same_module_c_shadow_fixture() []ast.File {
    int_type := call_test_ident('int')
    return [
        ast.File{
            name:  'foo.v'
            mod:   'foo'
            stmts: [
                ast.Stmt(ast.ModuleStmt{
                    name: 'foo'
                }),
                ast.Stmt(ast.FnDecl{
                    name:     'callee'
                    language: .c
                    typ:      ast.FnType{
                        params:      [
                            call_test_param('x', int_type),
                        ]
                        return_type: int_type
                    }
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'callee'
                    typ:   ast.FnType{
                        params:      [
                            call_test_param('x', int_type),
                        ]
                        return_type: int_type
                    }
                    stmts: [
                        ast.Stmt(ast.ReturnStmt{
                            exprs: [
                                call_test_ident('x'),
                            ]
                        }),
                    ]
                }),
                ast.Stmt(ast.FnDecl{
                    name:  'caller'
                    typ:   ast.FnType{
                        return_type: int_type
                    }
                    stmts: [
                        ast.Stmt(ast.ReturnStmt{
                            exprs: [
                                ast.Expr(ast.CallExpr{
                                    lhs:  call_test_ident('callee')
                                    args: [
                                        ast.Expr(ast.BasicLiteral{
                                            kind:  .number
                                            value: '1'
                                        }),
                                    ]
                                }),
                            ]
                        }),
                    ]
                }),
            ]
        },
    ]
}

fn call_test_func_value_ids(b &Builder, name string) []ValueID {
    idx := b.fn_index[name] or {
        assert false, 'missing SSA function ${name}'
        return []ValueID{}
    }
    func := b.mod.funcs[idx]
    mut ids := []ValueID{}
    for block_id in func.blocks {
        for value_id in b.mod.blocks[block_id].instrs {
            ids << value_id
        }
    }
    return ids
}

fn call_test_callees(b &Builder, name string) []string {
    mut callees := []string{}
    for value_id in call_test_func_value_ids(b, name) {
        value := b.mod.values[value_id]
        if value.kind != .instruction {
            continue
        }
        instr := b.mod.instrs[value.index]
        if instr.op != .call || instr.operands.len == 0 {
            continue
        }
        callee_id := instr.operands[0]
        if callee_id > 0 && callee_id < b.mod.values.len {
            callees << b.mod.values[callee_id].name
        }
    }
    return callees
}

fn test_build_all_from_flat_prefers_same_module_fn_over_bare_c_symbol() {
    files := make_same_module_c_shadow_fixture()
    flat := ast.flatten_files(files)
    env := types.Environment.new()
    mut mod := Module.new('same_module_c_shadow')
    mut b := Builder.new_with_env(mod, env)
    b.build_all_from_flat(&flat)

    assert call_test_callees(b, 'foo__caller') == ['foo__callee']
}