#include <cmath>
#include <cstdio>
#include <string>
#include <vector>
#include <thread>

#include "llama.h"
#include "main.h"

std::vector<llama_token> tokenize(const struct llama_model * model, const std::string & text, bool add_bos, bool special = false) {
    // upper limit for the number of tokens
    int n_tokens = text.length() + add_bos;
    std::vector<llama_token> result(n_tokens);
    n_tokens = llama_tokenize(model, text.data(), text.length(), result.data(), result.size(), add_bos, special);
    if (n_tokens < 0) {
        result.resize(-n_tokens);
        int check = llama_tokenize(model, text.data(), text.length(), result.data(), result.size(), add_bos, special);
        GGML_ASSERT(check == -n_tokens);
    } else {
        result.resize(n_tokens);
    }
    return result;
}

std::string token_to_piece(const struct llama_context * ctx, llama_token token) {
    std::vector<char> result(8, 0);
    const int n_tokens = llama_token_to_piece(llama_get_model(ctx), token, result.data(), result.size());
    if (n_tokens < 0) {
        result.resize(-n_tokens);
        int check = llama_token_to_piece(llama_get_model(ctx), token, result.data(), result.size());
        GGML_ASSERT(check == -n_tokens);
    } else {
        result.resize(n_tokens);
    }

    return std::string(result.data(), result.size());
}

void batch_add(
                 struct llama_batch & batch,
                        llama_token   id,
                          llama_pos   pos,
    const std::vector<llama_seq_id> & seq_ids,
                               bool   logits) {
    batch.token   [batch.n_tokens] = id;
    batch.pos     [batch.n_tokens] = pos,
    batch.n_seq_id[batch.n_tokens] = seq_ids.size();
    for (size_t i = 0; i < seq_ids.size(); ++i) {
        batch.seq_id[batch.n_tokens][i] = seq_ids[i];
    }
    batch.logits  [batch.n_tokens] = logits;

    batch.n_tokens++;
}

void batch_clear(struct llama_batch & batch) {
    batch.n_tokens = 0;
}

int generate(const char *model_path, const char *prompt) {
    // number of parallel batches
    int n_parallel = 1;

    // total length of the sequences including the prompt
    int n_len = 32;

    // init LLM
    llama_backend_init(true);

    // initialize the model

    llama_model_params model_params = llama_model_default_params();

    // model_params.n_gpu_layers = 99; // offload all layers to the GPU

    llama_model * model = llama_load_model_from_file(model_path, model_params);

    if (model == NULL) {
        fprintf(stderr , "%s: error: unable to load model\n" , __func__);
        return 1;
    }

    // tokenize the prompt

    std::vector<llama_token> tokens_list;
    tokens_list = tokenize(model, std::string(prompt), true);
    const int n_kv_req = tokens_list.size() + (n_len - tokens_list.size())*n_parallel;

    // initialize the context

    llama_context_params ctx_params = llama_context_default_params();

    ctx_params.seed  = 1234;
    ctx_params.n_ctx = n_kv_req;
    ctx_params.n_batch = std::max(n_len, n_parallel);
    ctx_params.n_threads       = std::thread::hardware_concurrency();
    ctx_params.n_threads_batch = ctx_params.n_threads;

    llama_context * ctx = llama_new_context_with_model(model, ctx_params);

    if (ctx == NULL) {
        fprintf(stderr , "%s: error: failed to create the llama_context\n" , __func__);
        return 1;
    }

    const int n_ctx    = llama_n_ctx(ctx);

    printf("\n%s: n_len = %d, n_ctx = %d, n_batch = %d, n_parallel = %d, n_kv_req = %d\n", __func__, n_len, n_ctx, ctx_params.n_batch, n_parallel, n_kv_req);

    // make sure the KV cache is big enough to hold all the prompt and generated tokens
    if (n_kv_req > n_ctx) {
        printf("%s: error: n_kv_req (%d) > n_ctx, the required KV cache size is not big enough\n", __func__,  n_kv_req);
        printf("%s:        either reduce n_parallel or increase n_ctx\n", __func__);
        return 1;
    }

    // print the prompt token-by-token

    fprintf(stderr, "\n");

    for (auto id : tokens_list) {
        fprintf(stderr, "%s", token_to_piece(ctx, id).c_str());
    }

    fflush(stderr);

    // create a llama_batch
    // we use this object to submit token data for decoding
    llama_batch batch = llama_batch_init(std::max(tokens_list.size(), (size_t)n_parallel), 0, 1);

    // evaluate the initial prompt
    for (size_t i = 0; i < tokens_list.size(); ++i) {
        batch_add(batch, tokens_list[i], i, { 0 }, false);
    }
    GGML_ASSERT(batch.n_tokens == (int) tokens_list.size());

    // llama_decode will output logits only for the last token of the prompt
    batch.logits[batch.n_tokens - 1] = true;

    if (llama_decode(ctx, batch) != 0) {
        printf("%s: llama_decode() failed\n", __func__);
        return 1;
    }

    // assign the system KV cache to all parallel sequences
    // this way, the parallel sequences will "reuse" the prompt tokens without having to copy them
    for (int32_t i = 1; i < n_parallel; ++i) {
        llama_kv_cache_seq_cp(ctx, 0, i, 0, batch.n_tokens);
    }

    if (n_parallel > 1) {
        printf("\n\n%s: generating %d sequences ...\n", __func__, n_parallel);
    }

    // main loop

    // we will store the parallel decoded sequences in this vector
    std::vector<std::string> streams(n_parallel);

    // remember the batch index of the last token for each parallel sequence
    // we need this to determine which logits to sample from
    std::vector<int32_t> i_batch(n_parallel, batch.n_tokens - 1);

    int n_cur    = batch.n_tokens;
    int n_decode = 0;

    const auto t_main_start = ggml_time_us();

    while (n_cur <= n_len) {
        // prepare the next batch
        batch_clear(batch);

        // sample the next token for each parallel sequence / stream
        for (int32_t i = 0; i < n_parallel; ++i) {
            if (i_batch[i] < 0) {
                // the stream has already finished
                continue;
            }

            auto   n_vocab = llama_n_vocab(model);
            auto * logits  = llama_get_logits_ith(ctx, i_batch[i]);

            std::vector<llama_token_data> candidates;
            candidates.reserve(n_vocab);

            for (llama_token token_id = 0; token_id < n_vocab; token_id++) {
                candidates.emplace_back(llama_token_data{ token_id, logits[token_id], 0.0f });
            }

            llama_token_data_array candidates_p = { candidates.data(), candidates.size(), false };

            const int   top_k = 40;
            const float top_p = 0.9f;
            const float temp  = 0.4f;

            llama_sample_top_k(ctx, &candidates_p, top_k, 1);
            llama_sample_top_p(ctx, &candidates_p, top_p, 1);
            llama_sample_temp (ctx, &candidates_p, temp);

            const llama_token new_token_id = llama_sample_token(ctx, &candidates_p);

            //const llama_token new_token_id = llama_sample_token_greedy(ctx, &candidates_p);

            // is it an end of stream? -> mark the stream as finished
            if (new_token_id == llama_token_eos(ctx) || n_cur == n_len) {
                i_batch[i] = -1;
                printf("\n");
                if (n_parallel > 1) {
                    printf("%s: stream %d finished at n_cur = %d", __func__, i, n_cur);
                }

                continue;
            }

            // if there is only one stream, we print immediately to stdout
            if (n_parallel == 1) {
                printf("%s", token_to_piece(ctx, new_token_id).c_str());
                fflush(stdout);
            }

            streams[i] += token_to_piece(ctx, new_token_id);

            i_batch[i] = batch.n_tokens;

            // push this new token for next evaluation
            batch_add(batch, new_token_id, n_cur, { i }, true);

            n_decode += 1;
        }

        // all streams are finished
        if (batch.n_tokens == 0) {
            break;
        }

        n_cur += 1;

        // evaluate the current batch with the transformer model
        if (llama_decode(ctx, batch)) {
            fprintf(stderr, "%s : failed to eval, return code %d\n", __func__, 1);
            return 1;
        }
    }

    printf("\n");

    if (n_parallel > 1) {
        printf("\n");

        for (int32_t i = 0; i < n_parallel; ++i) {
            printf("sequence %d:\n\n%s%s\n\n", i, prompt, streams[i].c_str());
        }
    }

    const auto t_main_end = ggml_time_us();

    printf("%s: decoded %d tokens in %.2f s, speed: %.2f t/s\n",
            __func__, n_decode, (t_main_end - t_main_start) / 1000000.0f, n_decode / ((t_main_end - t_main_start) / 1000000.0f));

    llama_print_timings(ctx);

    fprintf(stderr, "\n");

    llama_batch_free(batch);

    llama_free(ctx);
    llama_free_model(model);

    llama_backend_free();

    return 0;
}