/*
 * Copyright (c) 2015 Andrew Kelley
 *
 * This file is part of zig, which is MIT licensed.
 * See http://opensource.org/licenses/MIT
 */

#include "config.h"
#include "util.hpp"
#include "list.hpp"
#include "buffer.hpp"
#include "parser.hpp"
#include "tokenizer.hpp"
#include "error.hpp"

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <stdint.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <inttypes.h>

static int usage(const char *arg0) {
    fprintf(stderr, "Usage: %s [command] [options] target\n"
        "Commands:\n"
        "  build          create an executable from target\n"
        "  link           turn a .o file into an executable\n"
        "Options:\n"
        "  --output       output file\n"
        "  --version      print version number and exit\n"
        "  -Ipath         add path to header include path\n"
    , arg0);
    return EXIT_FAILURE;
}

static Buf *fetch_file(FILE *f) {
    int fd = fileno(f);
    struct stat st;
    if (fstat(fd, &st))
        zig_panic("unable to stat file: %s", strerror(errno));
    off_t big_size = st.st_size;
    if (big_size > INT_MAX)
        zig_panic("file too big");
    int size = (int)big_size;

    Buf *buf = buf_alloc_fixed(size);
    size_t amt_read = fread(buf_ptr(buf), 1, buf_len(buf), f);
    if (amt_read != (size_t)buf_len(buf))
        zig_panic("error reading: %s", strerror(errno));

    return buf;
}

static int build(const char *arg0, const char *in_file, const char *out_file, ZigList<char *> *include_paths) {
    static char cur_dir[1024];

    if (!in_file || !out_file)
        return usage(arg0);

    FILE *in_f;
    Buf *cur_dir_path;
    if (strcmp(in_file, "-") == 0) {
        in_f = stdin;
        char *result = getcwd(cur_dir, sizeof(cur_dir));
        if (!result)
            zig_panic("unable to get current working directory: %s", strerror(errno));
        cur_dir_path = buf_create_from_str(result);
    } else {
        in_f = fopen(in_file, "rb");
        if (!in_f)
            zig_panic("unable to open %s for reading: %s\n", in_file, strerror(errno));
        cur_dir_path = buf_dirname(buf_create_from_str(in_file));
    }

    Buf *in_data = fetch_file(in_f);

    fprintf(stderr, "Original source:\n");
    fprintf(stderr, "----------------\n");
    fprintf(stderr, "%s\n", buf_ptr(in_data));

    ZigList<Token> *tokens = tokenize(in_data, cur_dir_path);

    fprintf(stderr, "\nTokens:\n");
    fprintf(stderr, "---------\n");
    print_tokens(in_data, tokens);

    AstNode *root = ast_parse(in_data, tokens);
    assert(root);
    ast_print(root, 0);


    return 0;
}

enum ElfType {
    ElfTypeRelocatable,
    ElfTypeExecutable,
    ElfTypeShared,
    ElfTypeCore,
};

enum ElfArch {
    ElfArchSparc,
    ElfArchx86,
    ElfArchMips,
    ElfArchPowerPc,
    ElfArchArm,
    ElfArchSuperH,
    ElfArchIA_64,
    ElfArchx86_64,
    ElfArchAArch64,
};


enum ElfSectionType {
    SHT_NULL = 0,
    SHT_PROGBITS = 1,
    SHT_SYMTAB = 2,
    SHT_STRTAB = 3,
    SHT_RELA = 4,
    SHT_HASH = 5,
    SHT_DYNAMIC = 6,
    SHT_NOTE = 7,
    SHT_NOBITS = 8,
    SHT_REL = 9,
    SHT_SHLIB = 10,
    SHT_DYNSYM = 11,
    SHT_INIT_ARRAY = 14,
    SHT_FINI_ARRAY = 15,
    SHT_PREINIT_ARRAY = 16,
    SHT_GROUP = 17,
    SHT_SYMTAB_SHNDX = 18,
    SHT_LOOS = 0x60000000,
    SHT_HIOS = 0x6fffffff,
    SHT_LOPROC = 0x70000000,
    SHT_HIPROC = 0x7fffffff,
    SHT_LOUSER = 0x80000000,
    SHT_HIUSER = 0xffffffff,
};

struct Elf32SectionHeader {
    uint32_t name;
    uint32_t type;
    uint32_t flags;
    size_t addr;
    off_t offset;
    uint32_t size;
    uint32_t link;
    uint32_t info;
    uint32_t addralign;
    uint32_t entsize;
};

struct Elf64SectionHeader{
    uint32_t name;
    uint32_t type;
    uint64_t flags;
    size_t addr;
    off_t offset;
    uint64_t size;
    uint32_t link;
    uint32_t info;
    uint64_t addralign;
    uint64_t entsize;
};

struct Elf {
    bool is_64;
    bool is_little_endian;
    ElfType type;
    ElfArch arch;
    uint64_t entry_addr;
    uint64_t program_header_offset;
    uint64_t section_header_offset;
    int sh_entry_count;
    int string_section_index;
    union {
        Elf32SectionHeader *elf32_section_headers;
        Elf64SectionHeader *elf64_section_headers;
    };
};

static int parse_elf(Elf *elf, Buf *buf) {
    int len = buf_len(buf);
    if (len < 52) {
        return ErrorInvalidFormat;
    }

    char *ptr = buf_ptr(buf);
    static const int magic_size = 4;
    static const char magic[magic_size] = {0x7f, 'E', 'L', 'F'};
    if (memcmp(ptr, magic, magic_size) != 0) {
        return ErrorInvalidFormat;
    }
    ptr += magic_size;

    if (*ptr == 1) {
        elf->is_64 = false;
    } else if (*ptr == 2) {
        elf->is_64 = true;
        if (len < 64)
            return ErrorInvalidFormat;
    } else {
        return ErrorInvalidFormat;
    }
    ptr += 1;


    if (*ptr == 1) {
        elf->is_little_endian = true;
    } else if (*ptr == 2) {
        elf->is_little_endian = false;
        zig_panic("can only handle little endian");
    } else {
        return ErrorInvalidFormat;
    }
    ptr += 1;


    if (*ptr != 1) {
        return ErrorInvalidFormat;
    }

    uint16_t *type_number = (uint16_t *)&buf_ptr(buf)[0x10];
    if (*type_number == 1) {
        elf->type = ElfTypeRelocatable;
    } else if (*type_number == 2) {
        elf->type = ElfTypeExecutable;
    } else if (*type_number == 3) {
        elf->type = ElfTypeShared;
    } else if (*type_number == 4) {
        elf->type = ElfTypeCore;
    } else {
        return ErrorInvalidFormat;
    }

    uint16_t *arch = (uint16_t *)&buf_ptr(buf)[0x12];
    if (*arch == 0x02) {
        elf->arch = ElfArchSparc;
    } else if (*arch == 0x03) {
        elf->arch = ElfArchx86;
    } else if (*arch == 0x08) {
        elf->arch = ElfArchMips;
    } else if (*arch == 0x14) {
        elf->arch = ElfArchPowerPc;
    } else if (*arch == 0x28) {
        elf->arch = ElfArchArm;
    } else if (*arch == 0x2A) {
        elf->arch = ElfArchSuperH;
    } else if (*arch == 0x32) {
        elf->arch = ElfArchIA_64;
    } else if (*arch == 0x3E) {
        elf->arch = ElfArchx86_64;
    } else if (*arch == 0xb7) {
        elf->arch = ElfArchAArch64;
    } else {
        return ErrorInvalidFormat;
    }

    uint32_t *elf_vers = (uint32_t *)&buf_ptr(buf)[0x14];
    if (*elf_vers != 1) {
        return ErrorInvalidFormat;
    }

    ptr = &buf_ptr(buf)[0x18];
    if (elf->is_64) {
        elf->entry_addr = *((uint64_t *)ptr);
        ptr += 8;
        elf->program_header_offset = *((uint64_t *)ptr);
        ptr += 8;
        elf->section_header_offset = *((uint64_t *)ptr);
        ptr += 8;
    } else {
        elf->entry_addr = *((uint32_t *)ptr);
        ptr += 4;
        elf->program_header_offset = *((uint32_t *)ptr);
        ptr += 4;
        elf->section_header_offset = *((uint32_t *)ptr);
        ptr += 4;
    }

    // skip over flags
    ptr += 4;

    uint16_t header_size = *((uint16_t*)ptr);
    if ((elf->is_64 && header_size != 64) || (!elf->is_64 && header_size != 52)) {
        return ErrorInvalidFormat;
    }
    ptr += 2;

    uint16_t ph_entry_size = *((uint16_t*)ptr);
    ptr += 2;
    uint16_t ph_entry_count = *((uint16_t*)ptr);
    ptr += 2;
    uint16_t sh_entry_size = *((uint16_t*)ptr);
    ptr += 2;
    uint16_t sh_entry_count = *((uint16_t*)ptr);
    ptr += 2;
    uint16_t sh_name_index = *((uint16_t*)ptr);
    ptr += 2;

    elf->string_section_index = sh_name_index;
    if (elf->string_section_index >= sh_entry_count) {
        return ErrorInvalidFormat;
    }

    long sh_byte_count = ((long) sh_entry_size) * ((long) sh_entry_count);
    long end_sh = ((long)elf->section_header_offset) + sh_byte_count;
    long end_ph = ((long)elf->program_header_offset) + ((long) ph_entry_size) * ((long) ph_entry_count);

    if (len < end_sh || len < end_ph) {
        return ErrorInvalidFormat;
    }

    ptr = &buf_ptr(buf)[elf->section_header_offset];
    if (elf->is_64) {
        if (sh_entry_size != sizeof(Elf64SectionHeader)) {
            return ErrorInvalidFormat;
        }

        elf->elf64_section_headers = allocate<Elf64SectionHeader>(sh_entry_count);
        memcpy(elf->elf64_section_headers, ptr, sh_byte_count);
        elf->sh_entry_count = sh_entry_count;

        Elf64SectionHeader *string_section = &elf->elf64_section_headers[elf->string_section_index];
        if (string_section->type != SHT_STRTAB) {
            // not a string table
            return ErrorInvalidFormat;
        }

        // validate section types and offsets
        for (int i = 0; i < elf->sh_entry_count; i += 1) {
            Elf64SectionHeader *section = &elf->elf64_section_headers[i];

            if (section->type != SHT_NOBITS) {
                long file_end_offset = ((long)section->offset) + ((long)section->size);
                if (len < file_end_offset) {
                    return ErrorInvalidFormat;
                }
            }

        }

        for (int i = 0; i < elf->sh_entry_count; i += 1) {
            Elf64SectionHeader *section = &elf->elf64_section_headers[i];
            if (section->type == SHT_NULL)
                continue;
            long name_offset = section->name;
            ptr = &buf_ptr(buf)[string_section->offset + name_offset];
            fprintf(stderr, "section: %s\n", ptr);
            fprintf(stderr, "  start: 0x%" PRIx64 "\n", (uint64_t)section->offset);
            fprintf(stderr, "    end: 0x%" PRIx64 "\n", (uint64_t)section->offset + (uint64_t)section->size);

            if (section->type == SHT_SYMTAB) {
                fprintf(stderr, "  symtab\n");
            } else if (section->type == SHT_DYNSYM) {
                fprintf(stderr, "  dynsym\n");
                zig_panic("TODO SHT_DYNSYM");
            }
        }


    } else {
        if (sh_entry_size != sizeof(Elf32SectionHeader))
            return ErrorInvalidFormat;

        zig_panic("TODO 32-bit ELF");
    }



    return 0;
}

static int link(const char *arg0, const char *in_file, const char *out_file) {
    if (!in_file || !out_file)
        return usage(arg0);

    FILE *in_f;
    if (strcmp(in_file, "-") == 0) {
        in_f = stdin;
    } else {
        in_f = fopen(in_file, "rb");
        if (!in_f)
            zig_panic("unable to open %s for reading: %s\n", in_file, strerror(errno));
    }
    Buf *in_data = fetch_file(in_f);

    Elf elf = {0};
    int err;
    if ((err = parse_elf(&elf, in_data))) {
        fprintf(stderr, "unable to parse ELF: %s\n", err_str(err));
        return 1;
    }

    fprintf(stderr, "ELF is 64? %d\n", (int)elf.is_64);
    fprintf(stderr, "arch: %d\n", (int)elf.arch);
    fprintf(stderr, "exe? %d\n", (int)(elf.type == ElfTypeExecutable));
    fprintf(stderr, "entry: 0x%" PRIx64 "\n", elf.entry_addr);



    return 0;
}

enum Cmd {
    CmdNone,
    CmdBuild,
    CmdLink,
};

int main(int argc, char **argv) {
    char *arg0 = argv[0];
    char *in_file = NULL;
    char *out_file = NULL;
    ZigList<char *> include_paths = {0};

    Cmd cmd = CmdNone;
    for (int i = 1; i < argc; i += 1) {
        char *arg = argv[i];
        if (arg[0] == '-' && arg[1] == '-') {
            if (strcmp(arg, "--version") == 0) {
                printf("%s\n", ZIG_VERSION_STRING);
                return EXIT_SUCCESS;
            } else if (i + 1 >= argc) {
                return usage(arg0);
            } else {
                i += 1;
                if (strcmp(arg, "--output") == 0) {
                    out_file = argv[i];
                } else {
                    return usage(arg0);
                }
            }
        } else if (arg[0] == '-' && arg[1] == 'I') {
            include_paths.append(arg + 2);
        } else if (cmd == CmdNone) {
            if (strcmp(arg, "build") == 0) {
                cmd = CmdBuild;
            } else if (strcmp(arg, "link") == 0) {
                cmd = CmdLink;
            } else {
                fprintf(stderr, "Unrecognized command: %s\n", arg);
                return usage(arg0);
            }
        } else {
            switch (cmd) {
                case CmdNone:
                    zig_panic("unreachable");
                case CmdBuild:
                    if (!in_file) {
                        in_file = arg;
                    } else {
                        return usage(arg0);
                    }
                    break;
                case CmdLink:
                    if (!in_file) {
                        in_file = arg;
                    } else {
                        return usage(arg0);
                    }
                    break;
            }
        }
    }

    switch (cmd) {
        case CmdNone:
            return usage(arg0);
        case CmdBuild:
            return build(arg0, in_file, out_file, &include_paths);
            break;
        case CmdLink:
            return link(arg0, in_file, out_file);
            break;
    }
}