/**
 * @file Stb.cpp
 * @brief 编译器自带的 .stb 映像规范（写侧）+ 只读视图 + FNV-1a + sidecar
 * @author 
 * @date 2026-08-21
 */

#include "compiler/Stb.h"

#include <cstdio>
#include <cstring>
#include <fstream>

#include "compiler/Project.h"

namespace compiler {

uint64_t fnv1a64_update(uint64_t h, const uint8_t* data, size_t len) {
    for (size_t i = 0; i < len; ++i) {
        h ^= data[i];
        h *= kFnvPrime;
    }
    return h;
}

uint64_t fnv1a64(const uint8_t* data, size_t len) {
    return fnv1a64_update(kFnvBasis, data, len);
}

namespace {

    uint32_t get_le32(const uint8_t* p) {
        return static_cast<uint32_t>(p[0])
            | (static_cast<uint32_t>(p[1]) << 8)
            | (static_cast<uint32_t>(p[2]) << 16)
            | (static_cast<uint32_t>(p[3]) << 24);
    }

    uint64_t get_le64(const uint8_t* p) {
        uint64_t v = 0;
        for (int i = 0; i < 8; ++i) {
            v |= static_cast<uint64_t>(p[i]) << (8 * i);
        }
        return v;
    }

    // ---- SHA-256（FIPS 180-4）----

    const uint32_t kShaK[64] = {
        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
        0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
        0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
        0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
        0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
        0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
        0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
        0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
        0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
    };

    inline uint32_t rotr(uint32_t x, uint32_t n) { return (x >> n) | (x << (32 - n)); }

    struct Sha256 {
        uint32_t h[8] = {0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
                         0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19};
        uint64_t total = 0;
        uint8_t block[64];
        size_t block_len = 0;

        void update(const uint8_t* data, size_t len) {
            total += len;
            while (len > 0) {
                const size_t take = (block_len < 64) ? (64 - block_len) : 0;
                const size_t n = len < take ? len : take;
                if (n > 0) {
                    for (size_t i = 0; i < n; ++i) {
                        block[block_len + i] = data[i];
                    }
                    block_len += n;
                    data += n;
                    len -= n;
                    if (block_len == 64) {
                        process();
                        block_len = 0;
                    }
                } else {
                    break;
                }
            }
        }

        void process() {
            uint32_t w[64];
            for (int i = 0; i < 16; ++i) {
                w[i] = get_be32(block + i * 4);
            }
            for (int i = 16; i < 64; ++i) {
                const uint32_t s0 = rotr(w[i - 15], 7) ^ rotr(w[i - 15], 18) ^ (w[i - 15] >> 3);
                const uint32_t s1 = rotr(w[i - 2], 17) ^ rotr(w[i - 2], 19) ^ (w[i - 2] >> 10);
                w[i] = w[i - 16] + s0 + w[i - 7] + s1;
            }
            uint32_t a = h[0], b = h[1], c = h[2], d = h[3];
            uint32_t e = h[4], f = h[5], g = h[6], hh = h[7];
            for (int i = 0; i < 64; ++i) {
                const uint32_t s1 = rotr(e, 6) ^ rotr(e, 11) ^ rotr(e, 25);
                const uint32_t ch = (e & f) ^ (~e & g);
                const uint32_t t1 = hh + s1 + ch + kShaK[i] + w[i];
                const uint32_t s0 = rotr(a, 2) ^ rotr(a, 13) ^ rotr(a, 22);
                const uint32_t maj = (a & b) ^ (a & c) ^ (b & c);
                const uint32_t t2 = s0 + maj;
                hh = g;
                g = f;
                f = e;
                e = d + t1;
                d = c;
                c = b;
                b = a;
                a = t1 + t2;
            }
            h[0] += a; h[1] += b; h[2] += c; h[3] += d;
            h[4] += e; h[5] += f; h[6] += g; h[7] += hh;
        }

        void final(uint8_t out[32]) {
            const uint64_t bitlen = total * 8;
            const uint8_t pad = 0x80;
            update(&pad, 1);
            const uint8_t zeros[64] = {0};
            // 补零到 block_len == 56（跨块时先补满当前块再补）
            while (block_len != 56) {
                const size_t n = (block_len < 56) ? (56 - block_len) : (64 - block_len);
                update(zeros, n);
            }
            // 64 位大端比特长度
            for (int i = 0; i < 8; ++i) {
                const uint8_t b2[1] = {static_cast<uint8_t>((bitlen >> (56 - 8 * i)) & 0xFF)};
                update(b2, 1);
            }
            for (int i = 0; i < 8; ++i) {
                out[i * 4 + 0] = static_cast<uint8_t>((h[i] >> 24) & 0xFF);
                out[i * 4 + 1] = static_cast<uint8_t>((h[i] >> 16) & 0xFF);
                out[i * 4 + 2] = static_cast<uint8_t>((h[i] >> 8) & 0xFF);
                out[i * 4 + 3] = static_cast<uint8_t>(h[i] & 0xFF);
            }
        }

        static uint32_t get_be32(const uint8_t* p) {
            return (static_cast<uint32_t>(p[0]) << 24) | (static_cast<uint32_t>(p[1]) << 16) |
                   (static_cast<uint32_t>(p[2]) << 8) | static_cast<uint32_t>(p[3]);
        }
    };

}  // namespace

void sha256(const uint8_t* data, size_t len, uint8_t out[kSha256Size]) {
    Sha256 s;
    s.update(data, len);
    s.final(out);
}

void fill_model_id(const std::string& name, uint32_t version, char out[kModelIdSize]) {
    const std::string id = name + std::to_string(version);
    for (size_t i = 0; i < kModelIdSize; ++i) {
        out[i] = i < id.size() ? id[i] : '\0';
    }
}

StbView StbView::from(const uint8_t* buf, size_t len) {
    StbView v;
    v.buf_ = buf;
    v.len_ = len;
    if (buf == nullptr) {
        v.err_ = "null buffer";
        return v;
    }
    if (len < kHeaderSize) {
        v.err_ = "image too short";
        return v;
    }
    if (get_le32(buf + 0) != kMagic) {
        v.err_ = "bad magic";
        return v;
    }
    if (get_le32(buf + 4) != kVersion) {
        v.err_ = "bad version";
        return v;
    }
    v.cycle_limit_ = get_le32(buf + 8);
    v.dt_ms_ = get_le32(buf + 12);
    v.project_hash_ = get_le64(buf + 16);
    v.entry_fn_id_ = get_le32(buf + 24);
    v.n_globals_ = get_le32(buf + 28);
    v.n_consts_ = get_le32(buf + 44);
    v.n_funcs_ = get_le32(buf + 48);
    v.offset_code_ = get_le32(buf + 60);
    v.offset_fb_ = get_le32(buf + 64);
    v.offset_data_ = get_le32(buf + 68);

    // 段校验（12.13：文件尾 SHA-256[32] 在数据段之后）
    if (len < static_cast<size_t>(v.offset_data_) + kSha256Size) {
        v.err_ = "missing sha256 tail";
        return v;
    }
    const uint64_t offs[5] = {get_le32(buf + 52), get_le32(buf + 56), v.offset_code_,
                              v.offset_fb_, v.offset_data_};
    for (int i = 0; i < 5; ++i) {
        if (offs[i] < kHeaderSize || offs[i] > len - kSha256Size) {
            v.err_ = "segment offset out of range";
            return v;
        }
        if (i > 0 && offs[i] < offs[i - 1]) {
            v.err_ = "segment offsets not monotonic";
            return v;
        }
    }
    if (offs[1] - offs[0] != static_cast<uint64_t>(v.n_consts_) * kConstEntrySize) {
        v.err_ = "const table size mismatch";
        return v;
    }
    if (offs[2] - offs[1] != static_cast<uint64_t>(v.n_funcs_) * kFuncRowSize) {
        v.err_ = "function table size mismatch";
        return v;
    }
    if ((v.offset_fb_ - v.offset_code_) % 4 != 0) {
        v.err_ = "code segment not 4-byte aligned";
        return v;
    }
    if (v.entry_fn_id_ >= v.n_funcs_ && v.n_funcs_ != 0) {
        v.err_ = "entry fn_id out of range";
        return v;
    }
    v.ok_ = true;
    v.err_.clear();
    return v;
}

StbView StbView::from(const std::vector<uint8_t>& buf) {
    return from(buf.data(), buf.size());
}

ConstEntry StbView::const_entry(size_t i) const {
    ConstEntry e;
    if (ok_ && i < n_consts_) {
        const uint8_t* p = buf_ + offs_of_const() + i * kConstEntrySize;
        e.tag = get_le32(p);
        e.value = get_le64(p + 4);
    }
    return e;
}

uint32_t StbView::offs_of_const() const {
    // offset_const = offs[0]，由 from() 已校验的段起点
    return static_cast<uint32_t>(get_le32(buf_ + 52));
}

StbView::FuncRow StbView::func_row(size_t i) const {
    FuncRow r;
    if (ok_ && i < n_funcs_) {
        const uint8_t* p = buf_ + get_le32(buf_ + 56) + i * kFuncRowSize;
        r.nregs = get_le32(p + 0);
        r.code_offset = get_le32(p + 4);
        r.code_len = get_le32(p + 8);
    }
    return r;
}

const uint8_t* StbView::code_bytes() const {
    return ok_ ? buf_ + offset_code_ : nullptr;
}

size_t StbView::code_len() const {
    return ok_ ? offset_fb_ - offset_code_ : 0;
}

const uint8_t* StbView::data_bytes() const {
    return ok_ ? buf_ + offset_data_ : nullptr;
}

size_t StbView::data_len() const {
    return ok_ ? (len_ - kSha256Size) - offset_data_ : 0;
}

std::string StbView::model_id() const {
    if (!ok_) {
        return "";
    }
    std::string s(reinterpret_cast<const char*>(buf_ + 72), kModelIdSize);
    const size_t z = s.find('\0');
    if (z != std::string::npos) {
        s.resize(z);
    }
    return s;
}

bool StbView::model_matches(const std::string& name, uint32_t version) const {
    char want[kModelIdSize];
    fill_model_id(name, version, want);
    return std::memcmp(buf_ + 72, want, kModelIdSize) == 0;
}

bool StbView::sha_ok() const {
    if (!ok_) {
        return false;
    }
    const size_t content_len = len_ - kSha256Size;
    uint8_t digest[kSha256Size];
    sha256(buf_, content_len, digest);
    return std::memcmp(buf_ + content_len, digest, kSha256Size) == 0;
}

bool read_stb_file(const char* path, std::vector<uint8_t>* out, std::string* err) {
    std::ifstream in(path, std::ios::binary);
    if (!in) {
        if (err) {
            *err = "cannot open for read: " + std::string(path);
        }
        return false;
    }
    out->assign(std::istreambuf_iterator<char>(in), std::istreambuf_iterator<char>());
    return true;
}

bool write_stb_file(const char* path, const std::vector<uint8_t>& img, std::string* err) {
    std::FILE* f = std::fopen(path, "wb");
    if (f == nullptr) {
        if (err) {
            *err = "cannot open for write: " + std::string(path);
        }
        return false;
    }
    const bool ok = img.empty() || std::fwrite(&img[0], 1, img.size(), f) == img.size();
    std::fclose(f);
    if (!ok && err) {
        *err = "write failed: " + std::string(path);
    }
    return ok;
}

std::string make_sidecar(const std::vector<IoBinding>& bindings) {
    std::string out;
    for (const IoBinding& b : bindings) {
        char buf[64];
        out += b.is_input ? "[[io.input]]\n" : "[[io.output]]\n";
        out += "var = \"";
        out += b.var;
        out += "\"\n";
        std::snprintf(buf, sizeof buf, "slot = %u\n", static_cast<unsigned>(b.slot));
        out += buf;
        std::snprintf(buf, sizeof buf, "channel = %u\n", static_cast<unsigned>(b.channel));
        out += buf;
        std::snprintf(buf, sizeof buf, "bit = %u\n", static_cast<unsigned>(b.bit));
        out += buf;
        out += "\n";
    }
    return out;
}

bool write_sidecar_file(const char* path, const std::vector<IoBinding>& bindings,
                        std::string* err) {
    std::FILE* f = std::fopen(path, "wb");
    if (f == nullptr) {
        if (err) {
            *err = "cannot open for write: " + std::string(path);
        }
        return false;
    }
    const std::string s = make_sidecar(bindings);
    const bool ok = s.empty() || std::fwrite(s.data(), 1, s.size(), f) == s.size();
    std::fclose(f);
    if (!ok && err) {
        *err = "write failed: " + std::string(path);
    }
    return ok;
}

}  // namespace compiler