#include "../include/program.h"
#include "../include/std/mem.h"
#include "../include/std/alloc.h"
#include "../include/std/log.h"
#include <stdio.h>
#include <errno.h>
#include <assert.h>

/* TODO: If system is big-endian, then do endian conversion for all reads */

/* This matches SsaNumberType */
typedef enum {
    NUMBER_TYPE_INTEGER,
    NUMBER_TYPE_FLOAT
} NumberType;

typedef union {
    i64 integer;
    f64 floating;
} NumberUnion;

int amal_program_init(amal_program *self) {
    ignore_result_int(buffer_init(&self->data, NULL));
    ignore_result_int(buffer_init(&self->string_indices, NULL));
    self->intermediates_start = NULL;
    self->strings_start = NULL;
    self->read_index = 0;

    /*doc(Bytecode header)
        # Header layout
        |Size|Name         |Description                                                                 |
        |----|-------------|----------------------------------------------------------------------------|
        |4   |Magic number |The magic number used to identify an amalgam bytecode file.                 |
        |1   |Major version|The major version of the bytecode. Updates in this is a breaking change.    |
        |1   |Minor version|The minor version of the bytecode. Updates in this are backwards compatible.|
        |1   |Patch version|The patch version of the bytecode. Updates in this are only minor bug fixes.|
        The versions in the header only changes for every release, not every change.
    */

    const u32 magic_number = AMAL_PROGRAM_MAGIC_NUMBER;
    const u8 major_version = AMAL_PROGRAM_MAJOR_VERSION;
    const u8 minor_version = AMAL_PROGRAM_MINOR_VERSION;
    const u8 patch_version = AMAL_PROGRAM_PATCH_VERSION;

    return_if_error(buffer_append(&self->data, &magic_number, 4));
    return_if_error(buffer_append(&self->data, &major_version, 1));
    return_if_error(buffer_append(&self->data, &minor_version, 1));
    return_if_error(buffer_append(&self->data, &patch_version, 1));

    return 0;
}

void amal_program_deinit(amal_program *self) {
    buffer_deinit(&self->data);
    buffer_deinit(&self->string_indices);
}

int amal_program_append_bytecode(amal_program *self, Bytecode *bytecode) {
    return buffer_append(&self->data, bytecode->data.data, bytecode->data.size);
}

static usize bytes_left_to_read(amal_program *self) {
    assert(self->read_index <= self->data.size);
    return self->data.size - self->read_index;
}

static CHECK_RESULT int amal_program_read_header(amal_program *self) {
    u32 magic_number;
    u8 major_version;
    u8 minor_version;
    u8 patch_version;

    if(bytes_left_to_read(self) < sizeof(u32) + sizeof(u8) * 3)
        return AMAL_PROGRAM_INVALID_HEADER;

    am_memcpy(&magic_number, &self->data.data[self->read_index], sizeof(magic_number));
    self->read_index += sizeof(u32);
    am_memcpy(&major_version, &self->data.data[self->read_index], sizeof(major_version));
    self->read_index += sizeof(u8);
    am_memcpy(&minor_version, &self->data.data[self->read_index], sizeof(minor_version));
    self->read_index += sizeof(u8);
    am_memcpy(&patch_version, &self->data.data[self->read_index], sizeof(patch_version));
    self->read_index += sizeof(u8);

    if(magic_number != AMAL_PROGRAM_MAGIC_NUMBER)
        return AMAL_PROGRAM_INVALID_MAGIC_NUMBER;

    /*
        A program is only incompatible if the major version is newer than the version that is used to run it.
        TODO: Implement backwards compatible reads, starting from when the program bytecode breaks backwards compatibility
    */
    if(major_version > AMAL_PROGRAM_MAJOR_VERSION)
        return AMAL_PROGRAM_INCOMPATIBLE;

    return AMAL_PROGRAM_OK;
}

static CHECK_RESULT int amal_program_read_intermediates(amal_program *self) {
    u32 intermediates_size;
    /*u32 read_end;*/

    if(bytes_left_to_read(self) < sizeof(intermediates_size)) {
        amal_log_error("Not enough space in program to intermediates size");
        return AMAL_PROGRAM_INVALID_INTERMEDIATES;
    }

    am_memcpy(&intermediates_size, &self->data.data[self->read_index], sizeof(intermediates_size));
    self->read_index += sizeof(intermediates_size);

    if(bytes_left_to_read(self) < intermediates_size) {
        amal_log_error("Not enough space in program to read all intermediates");
        return AMAL_PROGRAM_INVALID_INTERMEDIATES_SIZE;
    }

    self->intermediates_start = &self->data.data[self->read_index];
    /*
    read_end = self->read_index + intermediates_size;
    while(self->read_index < read_end) {
        NumberType type;
        NumberUnion value;
        am_memcpy(&type, &self->data.data[self->read_index], sizeof(u8));
        am_memcpy(&value, &self->data.data[self->read_index + sizeof(u8)], sizeof(u64));
        self->read_index += sizeof(u8) + sizeof(u64);
    }
    */
    self->read_index += intermediates_size;

    return AMAL_PROGRAM_OK;
}

static CHECK_RESULT int amal_program_read_strings(amal_program *self) {
    u16 num_strings;
    u32 strings_size;
    u32 read_start;
    u32 read_end;
    u32 *string_index_ptr;

    if(bytes_left_to_read(self) < sizeof(num_strings))
        return AMAL_PROGRAM_INVALID_STRINGS;

    am_memcpy(&num_strings, &self->data.data[self->read_index], sizeof(num_strings));
    self->read_index += sizeof(num_strings);

    if(buffer_append_empty(&self->string_indices, num_strings) != 0)
        return AMAL_PROGRAM_STRING_ALLOC_FAILURE;
    string_index_ptr = (u32*)self->string_indices.data;

    if(bytes_left_to_read(self) < sizeof(strings_size))
        return AMAL_PROGRAM_INVALID_STRINGS;

    am_memcpy(&strings_size, &self->data.data[self->read_index], sizeof(strings_size));
    self->read_index += sizeof(strings_size);

    if(bytes_left_to_read(self) < strings_size)
        return AMAL_PROGRAM_INVALID_STRINGS_SIZE;

    read_start = self->read_index;
    read_end = read_start + strings_size;
    self->strings_start = &self->data.data[self->read_index];
    while(self->read_index < read_end) {
        u16 string_size;

        if(bytes_left_to_read(self) < sizeof(string_size))
            return AMAL_PROGRAM_INVALID_STRINGS;

        *string_index_ptr = self->read_index - read_start;
        ++string_index_ptr;
        am_memcpy(&string_size, &self->data.data[self->read_index], sizeof(string_size));
        self->read_index += sizeof(string_size);

        if(bytes_left_to_read(self) < string_size)
            return AMAL_PROGRAM_INVALID_STRINGS;

        self->read_index += string_size;
    }

    assert(self->read_index == read_end);
    return AMAL_PROGRAM_OK;
}

static CHECK_RESULT int amal_program_read_instructions(amal_program *self) {
    u32 instructions_size;
    u32 read_end;

    if(bytes_left_to_read(self) < sizeof(instructions_size))
        return AMAL_PROGRAM_INVALID_INSTRUCTIONS_SIZE;

    am_memcpy(&instructions_size, &self->data.data[self->read_index], sizeof(instructions_size));
    self->read_index += sizeof(instructions_size);

    if(bytes_left_to_read(self) < instructions_size)
        return AMAL_PROGRAM_INVALID_INSTRUCTIONS_SIZE;

    read_end = self->read_index + instructions_size;
    while(self->read_index < read_end) {
        AmalOpcode opcode;
        opcode = self->data.data[self->read_index];
        self->read_index += sizeof(AmalOpcodeType);
        switch(opcode) {
            case AMAL_OP_NOP:
                break;
            case AMAL_OP_SETZ:
                self->read_index += 1;
                break;
            case AMAL_OP_MOV:
                self->read_index += 2;
                break;
            case AMAL_OP_MOVI:
                self->read_index += 3;
                break;
            case AMAL_OP_MOVD:
                self->read_index += 3;
                break;
            case AMAL_OP_ADD:
                self->read_index += 3;
                break;
            case AMAL_OP_SUB:
                self->read_index += 3;
                break;
            case AMAL_OP_MUL:
                self->read_index += 3;
                break;
            case AMAL_OP_DIV:
                self->read_index += 3;
                break;
            case AMAL_OP_PUSH:
                self->read_index += 1;
                break;
            case AMAL_OP_PUSHI:
                self->read_index += 2;
                break;
            case AMAL_OP_PUSHD:
                self->read_index += 2;
                break;
            case AMAL_OP_CALL:
                self->read_index += 2;
                break;
            case AMAL_OP_CALLR:
                self->read_index += 1;
                break;
            case AMAL_OP_CMP:
                self->read_index += 3;
                break;
            case AMAL_OP_JZ:
                self->read_index += 3;
                break;
            case AMAL_OP_JMP:
                self->read_index += 2;
                break;
            case AMAL_OP_RET:
                break;
            case AMAL_OP_FUNC_START:
                break;
            case AMAL_OP_FUNC_END:
                break;
        }
    }

    return AMAL_PROGRAM_OK;
}

int amal_program_run(amal_program *self) {
    return_if_error(amal_program_read_header(self));
    while(bytes_left_to_read(self) > 0) {
        return_if_error(amal_program_read_intermediates(self));
        return_if_error(amal_program_read_strings(self));
        return_if_error(amal_program_read_instructions(self));
    }
    return AMAL_PROGRAM_OK;
}

int amal_program_save(amal_program *self, const char *filepath) {
    FILE *file;
    file = fopen(filepath, "wb");
    if(!file) {
        int err;
        err = errno;
        perror(filepath);
        return -err;
    }
    if(fwrite(self->data.data, 1, self->data.size, file) != self->data.size) {
        int err;
        err = errno;
        perror(filepath);
        return -err;
    }
    fclose(file);
    return 0;
}