// This file defines how to do type promotions during compilation

#include "../ast.h"
#include "../environment.h"
#include "../stdlib/datatypes.h"
#include "../stdlib/text.h"
#include "../typecheck.h"
#include "../types.h"
#include "compilation.h"

static Text_t quoted_str(const char *str) { return Text$quoted(Text$from_str(str), false, Text("\"")); }

public
bool promote(env_t *env, ast_t *ast, Text_t *code, type_t *actual, type_t *needed) {
    if (type_eq(actual, needed)) return true;

    if (!can_promote(actual, needed)) return false;

    if (needed->tag == ClosureType && actual->tag == FunctionType) {
        *code = Texts("((Closure_t){", *code, ", NULL})");
        return true;
    }

    // Empty promotion:
    type_t *more_complete = most_complete_type(actual, needed);
    if (more_complete) return true;

    // Serialization/deserialization:
    if (!type_eq(non_optional(value_type(needed)), Type(ListType, Type(ByteType)))
        || !type_eq(non_optional(value_type(actual)), Type(ListType, Type(ByteType)))) {
        if (type_eq(needed, Type(ListType, Type(ByteType)))) {
            *code = Texts("generic_serialize((", compile_declaration(actual, Text("[1]")), "){", *code, "}, ",
                          compile_type_info(actual), ")");
            return true;
        } else if (type_eq(actual, Type(ListType, Type(ByteType)))) {
            *code = Texts("({ ", compile_declaration(needed, Text("deserialized")),
                          ";\n"
                          "generic_deserialize(",
                          *code, ", &deserialized, ", compile_type_info(needed),
                          ");\n"
                          "deserialized; })");
            return true;
        }
    }

    // Optional promotion:
    if (needed->tag == OptionalType && type_eq(actual, Match(needed, OptionalType)->type)) {
        *code = promote_to_optional(actual, *code);
        return true;
    }

    // Optional -> Bool promotion
    if (actual->tag == OptionalType && needed->tag == BoolType) {
        *code = Texts("(!", check_none(actual, *code), ")");
        return true;
    }

    // Lang to Text_t:
    if (actual->tag == TextType && needed->tag == TextType && streq(Match(needed, TextType)->lang, "Text")) return true;

    // Automatic optional checking for nums:
    if (needed->tag == NumType && actual->tag == OptionalType && Match(actual, OptionalType)->type->tag == NumType) {
        int64_t line = get_line_number(ast->file, ast->start);
        *code = Texts("({ ", compile_declaration(actual, Text("opt")), " = ", *code, "; ", "if unlikely (",
                      check_none(actual, Text("opt")), ")\n", "#line ", line, "\n", "fail_source(",
                      quoted_str(ast->file->filename), ", ", (int64_t)(ast->start - ast->file->text), ", ",
                      (int64_t)(ast->end - ast->file->text), ", ",
                      "Text(\"This was expected to be a value, but it's none\"));\n",
                      optional_into_nonnone(actual, Text("opt")), "; })");
        return true;
    }

    // Numeric promotions/demotions
    if ((is_numeric_type(actual) || actual->tag == BoolType) && (is_numeric_type(needed) || needed->tag == BoolType)) {
        arg_ast_t *args = new (arg_ast_t, .value = LiteralCode(*code, .type = actual));
        binding_t *constructor = get_constructor(
            env, needed, args, env->current_type != NULL && type_eq(env->current_type, value_type(needed)));
        if (constructor) {
            DeclareMatch(fn, constructor->type, FunctionType);
            if (fn->args->next == NULL) {
                *code = Texts(constructor->code, "(", compile_arguments(env, ast, fn->args, args), ")");
                return true;
            }
        }
    }

    if (needed->tag == EnumType) {
        const char *tag = enum_single_value_tag(needed, actual);
        binding_t *b = get_binding(Match(needed, EnumType)->env, tag);
        assert(b && b->type->tag == FunctionType);
        // Single-value enum constructor:
        if (!promote(env, ast, code, actual, Match(b->type, FunctionType)->args->type)) return false;
        *code = Texts(b->code, "(", *code, ")");
        return true;
    }

    // Text_t to C String
    if (actual->tag == TextType && type_eq(actual, TEXT_TYPE) && needed->tag == CStringType) {
        *code = Texts("Text$as_c_string(", *code, ")");
        return true;
    }

    // Automatic dereferencing:
    if (actual->tag == PointerType && can_promote(Match(actual, PointerType)->pointed, needed)) {
        *code = Texts("*(", *code, ")");
        return promote(env, ast, code, Match(actual, PointerType)->pointed, needed);
    }

    // Stack ref promotion:
    if (actual->tag == PointerType && needed->tag == PointerType) return true;

    // Cross-promotion between tables with default values and without
    if (needed->tag == TableType && actual->tag == TableType) return true;

    if (needed->tag == ClosureType && actual->tag == ClosureType) return true;

    if (needed->tag == FunctionType && actual->tag == FunctionType) {
        *code = Texts("(", compile_type(needed), ")", *code);
        return true;
    }

    return false;
}

public
Text_t compile_to_type(env_t *env, ast_t *ast, type_t *t) {
    assert(!is_incomplete_type(t));

    if (t->tag == EnumType) {
        env = with_enum_scope(env, t);
    }

    if (ast->tag == Block && Match(ast, Block)->statements && !Match(ast, Block)->statements->next) {
        ast = Match(ast, Block)->statements->ast;
    }

    if (ast->tag == Int && is_numeric_type(non_optional(t))) {
        return compile_int_to_type(env, ast, t);
    } else if (ast->tag == Num && t->tag == NumType) {
        double n = Match(ast, Num)->n;
        switch (Match(t, NumType)->bits) {
        case TYPE_NBITS64: return Text$from_str(String(hex_double(n)));
        case TYPE_NBITS32: return Text$from_str(String(hex_double(n), "f"));
        default: code_err(ast, "This is not a valid number bit width");
        }
    } else if (ast->tag == None) {
        if (t->tag != OptionalType) code_err(ast, "This is not supposed to be an optional type");
        else if (Match(t, OptionalType)->type == NULL)
            code_err(ast, "I don't know what kind of `none` this is supposed to "
                          "be!\nPlease "
                          "tell me by declaring a variable like `foo : Type = none`");
        return compile_none(t);
    } else if (t->tag == PointerType && (ast->tag == HeapAllocate || ast->tag == StackReference)) {
        return compile_typed_allocation(env, ast, t);
    } else if (t->tag == ListType && ast->tag == List) {
        return compile_typed_list(env, ast, t);
    } else if (t->tag == TableType && ast->tag == Table) {
        return compile_typed_table(env, ast, t);
    }

    type_t *actual = get_type(env, ast);

    // Edge case: there are some situations where a method call needs to have
    // the `self` value get compiled to a specific type that can't be fully
    // inferred from the expression itself. We can infer what the specific type
    // should be from what we know the specific type of the return value is,
    // but it requires a bit of special logic.
    // For example:
    //    x : [Int?] = [none].sorted()
    // Here, we know that `[none]` is `[Int?]`, but we need to thread that
    // information through the compiler using an `ExplicitlyTyped` node.
    if (ast->tag == MethodCall) {
        DeclareMatch(methodcall, ast, MethodCall);
        type_t *self_type = get_type(env, methodcall->self);
        // Currently, this is only implemented for cases where you have the
        // return type and the self type equal to each other, because that's the
        // main case I care about with list and set methods (e.g.
        // `List.sorted()`)
        if (is_incomplete_type(self_type) && type_eq(self_type, actual)) {
            type_t *completed_self = most_complete_type(self_type, t);
            if (completed_self) {
                ast_t *explicit_self =
                    WrapAST(methodcall->self, ExplicitlyTyped, .ast = methodcall->self, .type = completed_self);
                ast_t *new_methodcall =
                    WrapAST(ast, MethodCall, .self = explicit_self, .name = methodcall->name, .args = methodcall->args);
                return compile_to_type(env, new_methodcall, t);
            }
        }
    }

    // Promote values to views-of-values if needed:
    if (t->tag == PointerType && Match(t, PointerType)->is_stack && actual->tag != PointerType) {
        if (type_eq(actual, Match(t, PointerType)->pointed) && can_be_mutated(env, ast))
            return Texts("&(", compile_lvalue(env, ast), ")");
    }

    if (!is_incomplete_type(actual)) {
        Text_t code = compile(env, ast);
        if (promote(env, ast, &code, actual, t)) return code;
    }

    arg_ast_t *constructor_args = new (arg_ast_t, .value = ast);
    binding_t *constructor = get_constructor(env, t, constructor_args, true);
    if (constructor) {
        arg_t *arg_spec = Match(constructor->type, FunctionType)->args;
        return Texts(constructor->code, "(", compile_arguments(env, ast, arg_spec, constructor_args), ")");
    }

    code_err(ast, "I expected a ", type_to_text(t), " here, but this is a ", type_to_text(actual));
}