#pragma once

#include "ime_session.h"
#include "input_session_types.h"
#include "candidate_queries.h"
#include "punctuation_policy.h"
#include "online_request_guard.h"
#include "../local_modes/date_time_query.h"
#include "../english/english_dictionary.h"
#include "word_item.h"
#include "../quanpin/engine.h"

#include <cstddef>
#include <cstdint>
#include <functional>
#include <memory>
#include <optional>
#include <string>
#include <vector>

namespace metasequoia
{
// Platform-neutral composition session shared by the native frontends. It owns an ImeSession and
// applies the key-handling and commit policy that each frontend would otherwise reimplement, so a
// frontend only has to translate platform key events into these calls.
class InputSession
{
  public:
    // Frontends pass their persisted options at session creation so every platform uses the same
    // engine configuration and commit policy.
    explicit InputSession(SchemeType scheme_type = SchemeType::Quanpin, unsigned quanpin_autocorrect_types = 0,
                          bool helpcode_enabled = true, bool chinese_punctuation_enabled = true,
                          bool candidate_learning_enabled = true, RuntimePaths paths = RuntimePaths::legacy());
    InputSession(SchemeType scheme_type, const ShuangpinProfile &shuangpin_profile,
                 RuntimePaths paths = RuntimePaths::legacy());

    // Feeds one lowercase ASCII letter or an in-composition apostrophe. Other input is rejected as
    // unhandled so the frontend can pass it through to the client application.
    KeyResult handle_character(char character, bool shift_only = false);
    // Applies a command. Every command is unhandled while no composition is active, which keeps
    // Backspace and Escape working normally in the client application.
    KeyResult handle_command(Command command);
    // Maps the visible 1-9 candidate keys and Chinese punctuation independently of platform UI.
    KeyResult handle_candidate_key(char character);
    KeyResult handle_punctuation(char character);
    // Commit the selected prefix and retain any unconsumed pinyin. Hosts insert
    // KeyResult::commit and then render the remaining preedit from this session.
    KeyResult select_candidate(std::size_t index);
    // Flush all remaining input for punctuation, scheme changes and host passthrough.
    KeyResult finish_composition(std::size_t first_index = 0);
    KeyResult select_candidate(const std::string &candidate);
    KeyResult select_candidate_edge(std::size_t index, CandidateEdge edge);
    KeyResult pin_candidate(std::size_t index);
    KeyResult remove_candidate(std::size_t index);
    KeyResult set_candidate_position(std::size_t index, int position);
    void enable_fixed_positions();
    void set_shuangpin_helpcode_enabled(bool enabled);
    // 双拼末尾辅助码的触发方式。direct（默认）按输入形状认辅码：完整音节后多一个键是单码，末尾两键带
    // 大写是双码。关掉后改由引导键触发：宿主把触发键（反引号或分号）换成 kEndMarker 交进来，
    // uppercase_trigger 开着时完整音节后的大写字母也开一段，见 FanyImeMidSentenceHelpcode::kEndMarker。
    void set_shuangpin_helpcode_triggers(bool direct, bool uppercase_trigger);
    // 宿主在把触发键换成 kEndMarker 之前问这一句：双拼辅助码开着、关着直接、没开直接辅助码，且光标在
    // 输入串末尾、前面是一个个完整的双拼音节。
    bool accepts_end_helpcode_marker_at(std::size_t caret) const;
    // 句中辅助码（双拼），见 core/syllable_helpcode.h。默认关闭。
    void set_mid_sentence_helpcode_enabled(bool enabled);
    // 宿主在决定是否把反引号当作编码键之前问这一句：开关开着、双拼，且光标前这一节能接一段句中
    // 辅助码（光标可以在句中，见 FanyImeMidSentenceHelpcode::AcceptsMarkerAt）。不满足时反引号
    // 仍按标点处理。不带参数的版本按会话自己的光标；光标由宿主维护时传宿主的光标。
    bool accepts_mid_sentence_helpcode_marker() const;
    bool accepts_mid_sentence_helpcode_marker_at(std::size_t caret) const;
    // 双拼直接辅助码（万象式，不要引导键，见 engine/direct_helpcode/）。默认关闭；开着时末尾辅助码
    // 和反引号句中辅助码都让位给它。
    // 句中辅助码的大写触发：完整音节后的大写字母相当于「反引号 + 这个字母」（第二码规则不变），见
    // FanyImeMidSentenceHelpcode::StartsUppercaseBlock。只在句中辅助码开着、直接辅助码关着时生效。
    void set_mid_sentence_uppercase_trigger_enabled(bool enabled);
    void set_direct_helpcode_enabled(bool enabled);
    bool direct_helpcode_enabled() const
    {
        return direct_helpcode_enabled_;
    }
    // 句中四码用什么结束：补 /（默认）、第二位辅码大写，可以都开。/ 关着时不再是编码键。
    void set_direct_helpcode_markers(bool slash, bool uppercase);
    // 宿主在决定是否把 / 当作编码键（四码后的终止键）之前问这一句，规则见
    // FanyImeDirectHelpcode::AcceptsSlashAt。不满足时 / 仍按标点处理。
    bool accepts_direct_helpcode_slash_at(std::size_t caret) const;
    // 当前输入带着生效的句中辅助码约束：候选是筛过的，排位不能当调频的参照。
    bool has_mid_sentence_helpcode() const;
    // 同一输入去掉句中辅助码约束后的引擎候选。用户下次不敲辅助码时看到的就是这份排序，
    // 调频要在这份里给选中的词挪位置；在筛过的列表里它往往已经排第一，调了等于没调。
    // 没有约束时就是当前引擎候选。
    std::vector<WordItem> candidates_without_mid_sentence_helpcode();
    void set_quanpin_helpcode_enabled(bool enabled);
    static bool is_supported_helpcode_schema(const std::string &schema);
    bool set_helpcode_schema(const std::string &schema);
    // Compatibility default for subsequently created sessions.
    static bool select_helpcode_schema(const std::string &schema);
    bool set_frequency_adjustment(FrequencyAdjustmentOptions options);
    const FrequencyAdjustmentOptions &frequency_adjustment() const;
    void set_local_mode_options(LocalModeOptions options);
    const LocalModeOptions &local_mode_options() const;
    bool set_english_input_options(EnglishInputOptions options);
    const EnglishInputOptions &english_input_options() const;
    void set_mixed_expressive_options(MixedExpressiveOptions options);
    void set_wubi_input_options(metasequoia::WubiInputOptions options);
    // 读回当前五笔设置：公开 Session 的运行期开关要按字段改，不能整份覆盖（否则会把另一个
    // 独立开关复位）。
    const metasequoia::WubiInputOptions &wubi_input_options() const;
    const MixedExpressiveOptions &mixed_expressive_options() const;
    void set_dedicated_english_mode(bool enabled);
    bool dedicated_english_mode() const;
    LocalInputMode local_input_mode() const;
    void set_local_date_time_provider(std::function<local_modes::LocalDateTime()> provider);
    std::optional<OnlineQuery> online_query() const;
    bool apply_online_candidate(const OnlineQuery &query, std::string candidate, CandidateSource source);

    SchemeType scheme_type() const;
    unsigned quanpin_autocorrect_types() const;
    bool helpcode_enabled() const;
    bool chinese_punctuation_enabled() const;
    bool candidate_learning_enabled() const;
    // Switching schemes discards the current composition. A frontend that promises to preserve
    // typed text must commit it before calling this method.
    void switch_scheme(SchemeType scheme_type);
    SchemeType scheme() const;

    bool has_composition() const;
    const std::string &preedit() const;
    std::string editing_text() const;
    std::size_t caret_position() const;
    const std::string &raw_segmentation() const;
    const std::string &normalized_segmentation() const;
    const std::vector<WordItem> &candidates() const;
    // Advanced composition operations for hosts with their own asynchronous text insertion.
    // They share the same engine/configuration as the portable character/command API.
    struct SelectionTransition
    {
        bool continues_composition = false;
        // 刚选中的候选由五笔码表产出。上屏推进与造词都按它决定：五笔候选一次消耗整串编码，
        // 拼音候选则只消耗自己那段、把剩余字母继续留在组合里。混输组合里两类候选共存，
        // 不能再按会话方案一刀切。
        bool wubi_native = false;
        std::string full_pure_pinyin;
        std::string current_segmentation;
        std::string current_segmentation_with_cases;
        std::string selected_canonical_pinyin;
        // Raw spelling the selection consumed from the active scheme's input,
        // in the exact form the user typed it. A host that lets the user retract
        // a selected segment must replay this spelling, not the pre-selection
        // raw: the pre-selection raw also contains suffix characters the user
        // may have deleted since the selection. Sources that consume no input
        // (cloud, associative, whole-word commits) leave it empty.
        std::string consumed_raw_input_with_cases;
    };

    struct CloudQueryState
    {
        bool should_query = false;
        std::string query_text;
        std::string cache_key;
        std::string committed_pinyin;
    };

    struct CreatingWordProgress
    {
        std::string pinyin;
        std::string word;
        std::string preedit;
        bool completed = false;
        bool can_store = false;
    };

    void handle_engine_key(ImeKeyCode vk, ImeModifierMask modifiers_down, ImeCharacter wch);
    void recompute_candidates();
    // Moves the caret without editing the raw string. nullopt = end of string (full-string
    // decoding, the default). The value is clamped to [0, editing_text().size()]. Setting it
    // only updates state; candidates re-decode by the new boundary on the next
    // recompute_candidates() or key handling.
    void set_caret(std::optional<std::size_t> caret);
    // Raw length consumed by the current decode: the caret moved onto the last complete
    // syllable-unit boundary at or before it (floor). A caret inside the first unit rounds up to
    // the end of that unit instead, so prefix_end() == 0 means caret == 0. The caret being
    // unset, or a scheme without the unit model (segment_raw_boundaries() empty), decodes the
    // whole string and this equals the raw length.
    std::size_t prefix_end() const;
    // raw[prefix_end, size) with its original casing: the pending input this decode did not
    // consume. Empty unless the caret prefix is strictly shorter than the raw string.
    std::string pending_suffix() const;
    SchemeType current_scheme_type() const;

    void reset_state();
    void reset_cache();
    // 神经重排结果回来后用：只失效整句排序，词库和切分缓存保持热，且不在这里重算，
    // 由调用方接着 recompute_candidates()。
    void reset_sentence_cache();

    const std::vector<WordItem> &get_candidates() const;
    bool can_expand_initial_candidates() const;
    bool expand_initial_candidates();
    std::optional<WordItem> find_candidate(const std::string &key, const std::string &value);

    const std::string &get_pinyin_sequence() const;
    const std::string &get_pinyin_sequence_with_cases() const;
    const std::string &get_pure_pinyin_sequence() const;
    const std::string &get_pinyin_segmentation() const;
    std::string get_pinyin_segmentation_with_cases() const;
    // 双拼会话的两种预编辑切分，不受 set_shuangpin_preedit_uses_raw 影响：raw 是按键原串的
    // 切分（ni'hc），quanpin 是转换后的全拼切分（ni'hao），两者音节数一致、辅助码装饰相同。
    // 非双拼会话两者都为空。
    struct ShuangpinPreeditForms
    {
        std::string raw;
        std::string quanpin;
    };
    ShuangpinPreeditForms get_shuangpin_preedit_forms() const;
    // Offsets in get_pinyin_sequence_with_cases() where one input unit starts,
    // always including 0 (when non-empty) and raw.size(). A unit is one syllable:
    // the `ma` of ni'hao'ma, one 1-2 key syllable in shuangpin. Schemes and
    // local modes without the unit model (wubi, japanese, U/K/E/M/J/Y/R and the
    // dedicated English scheme) return an empty vector, and hosts then fall back
    // to single-character editing. An active autocorrect/helpcode display is
    // mapped back to the raw spans the engine actually cut, so a deleted unit
    // can never leave half a segment or a stray separator behind. Consumed by
    // segment deletion (Ctrl+Backspace), so any later caret-movement feature
    // must use this same boundary set instead of re-deriving one.
    std::vector<std::size_t> segment_raw_boundaries() const;
    std::string get_quanpin() const;
    bool is_all_complete_pure_pinyin() const;
    // 整串输入能不能读成拼音：全拼按「完整音节或音节前缀」（含简拼声母，bus = bu + s）切完整串，
    // 双拼按完整音节码、末尾允许单独一个声母键。不要求音节完整，也不看词库有没有词。混输里用它
    // 决定英文前缀补全词的默认位置：能读成拼音的输入，用户多半在打中文，补全词默认退到首页末位。
    bool reads_as_pinyin() const;
    // The current composition is a complete four-letter wubi code the wubi table answered with
    // exactly one row. Hosts decide whether to auto-commit on this; the engine only reports the fact.
    // The pinyin candidates mixed input appends are deliberately not counted: a code the table did
    // not answer is not a unique wubi code, and committing a pinyin answer as one would take away
    // the extra letters mixed input exists to allow.
    bool wubi_unique_four_code() const;
    // The current composition is a complete four-letter wubi code the wubi table answered, regardless
    // of how many candidates it has. Hosts use it to commit the first candidate when the user types
    // past the fourth letter: a complete code that keeps growing must not silently swallow the extra
    // letters. In mixed input the appended pinyin candidates do not count; only the code's own rows
    // make it complete. See wubi_unique_four_code for the uniqueness part.
    bool wubi_four_code_is_complete() const;
    bool has_active_helpcode() const;

    void set_pinyin_sequence(const std::string &pinyin_sequence);
    void set_pinyin_sequence_with_cases(const std::string &pinyin_sequence);
    // Marks the pending sequence as a special mode's literal input on a wubi session (T mode's
    // Tdate, V mode's V1+2): kept as typed, never queried, never a complete code. Applies to the
    // sequence set alongside it and is dropped with it, so a host that does not call it gets an
    // ordinary code. Other schemes keep every typed character anyway and ignore it.
    void set_wubi_literal_input(bool literal);

    int store_user_phrase(std::string pinyin, std::string word);
    int store_user_phrase_from_canonical_pinyin(std::string pinyin, std::string word);
    // 混输组合里五笔与拼音候选共存，删除必须由调用方指明候选自己的方案，不能按会话方案。
    int remove_candidate(std::string pinyin, std::string word, SchemeType scheme);
    int cache_dynamic_candidate(const std::string &pinyin, const std::string &word, CandidateSource source);
    SelectionTransition advance_composition_after_selection(const std::string &selected_pinyin,
                                                            const std::string &selected_word,
                                                            const std::string &selected_canonical_pinyin,
                                                            SchemeType selected_scheme = SchemeType::Quanpin);
    CloudQueryState get_cloud_query_state() const;
    CreatingWordProgress update_creating_word_progress(const std::string &current_pinyin,
                                                       const std::string &current_word,
                                                       const std::string &selected_word,
                                                       const SelectionTransition &selection_transition) const;

    void set_quanpin_autocorrect_types(unsigned autocorrect_types);
    void set_fuzzy_pinyin_options(metasequoia::FuzzyPinyinOptions options)
    {
        engine_.set_fuzzy_pinyin_options(options);
    }
    void set_sentence_association(const SentenceAssociationOptions &options)
    {
        engine_.set_sentence_association(options);
    }
    void set_rescoring_context(std::string context)
    {
        engine_.set_rescoring_context(std::move(context));
    }
    void set_chinese_punctuation_enabled(bool enabled)
    {
        chinese_punctuation_enabled_ = enabled;
    }
    void set_candidate_learning_enabled(bool enabled)
    {
        candidate_learning_enabled_ = enabled;
    }
    void set_shuangpin_preedit_uses_raw(bool enabled)
    {
        shuangpin_preedit_uses_raw_ = enabled;
    }

  private:
    const QueryRequest &request() const;
    // 拼音类方案的预编辑切分；shuangpin_raw 决定双拼显示按键原串还是转换后的全拼。
    std::string build_pinyin_segmentation_with_cases(bool shuangpin_raw) const;
    bool is_shuangpin() const;
    bool is_wubi() const;
    // 候选是否由五笔码表产出。混输组合里五笔候选在前、拼音候选追加在后，调频、删除、固定
    // 位置与上屏推进都按候选自己的方案走，不再按会话方案一刀切。
    static bool is_wubi_native_candidate(const WordItem &item);
    // 当前列表里五笔码表候选的条数；顶字与四码自动上屏只认它，追加的拼音候选不算。
    std::size_t wubi_native_candidate_count() const;
    bool is_japanese() const;
    void clear_pending_sequence();
    void apply_pending_sequence();

    KeyResult commit(std::size_t index);
    KeyResult handle_local_character(char character);
    KeyResult insert_at_caret(char character);
    // 光标停在 caret 处时大写字母 character 能否作为句中辅助码收下：紧跟在反引号之后（第一码），
    // 或紧跟在「反引号 + 第一码」之后（第二码）。
    bool accepts_mid_sentence_code_at(std::size_t caret, char character) const;
    KeyResult edit_at_caret(Command command);
    KeyResult replace_editing_text(std::string text, std::size_t caret);
    std::optional<std::size_t> caret_;
    // Last complete unit boundary at or before the caret; only consumes segment_raw_boundaries()
    // (segmentation contract #187). A caret inside the first unit rounds up to that unit's end,
    // so only caret == 0 yields 0. Caret unset or no unit model yields the full raw length.
    std::size_t quantized_prefix_end() const;
    // Decodes the quantized caret prefix into prefix_candidates_ when it is strictly shorter
    // than the raw string, caching by prefix so unchanged keystrokes skip the extra query.
    void refresh_prefix_candidates();
    std::vector<WordItem> prefix_candidates_;
    // Lowercased prefix the cache was built from; also feeds mixed-candidate association so
    // English/emoji suggestions follow the string being converted.
    std::string prefix_query_input_;
    // True while candidates()/mixed assembly must read prefix_candidates_ instead of engine_.
    bool prefix_candidates_active_ = false;
    std::optional<std::string> update_local_candidates();
    void update_mixed_candidates();
    void apply_candidate_positions(std::vector<WordItem> &items);
    std::string position_context(bool english, bool wubi) const;
    bool fixed_positions_enabled_ = false;
    void update_dedicated_english_candidates();
    void reset_composition();
    void discard_abandoned_phrase_progress();
    std::optional<std::string> learn_candidate(std::size_t index);
    // 当前组合可以混入快捷短语时返回它的编码：全拼/双拼、非本地模式、未造词、无光标前缀和
    // 辅助码，且原始输入全是小写字母。
    std::optional<std::string> quick_phrase_code() const;
    // candidates() 返回混排列表（固定位置、英文/表情/颜文字混排任一开启）的条件。
    bool mixed_candidates_active() const;
    // 选中快捷短语时把组前移，越过组选普通候选时把组后移。
    std::optional<std::string> learn_quick_phrase_order(std::size_t index);
    // 词格 / Google 解码器猜出来的整句在词库里没有对应行，选中后落成一条用户词组。
    std::optional<std::string> learn_sentence_candidate(const WordItem &selected);
    std::optional<std::string> adjust_candidate_frequency(std::size_t index, FrequencyAdjustmentOptions options,
                                                          bool force_top);
    // 拼音候选的调频，排位参照 ranked 而不是当前列表；句中辅助码组合用不带约束的候选作参照。
    std::optional<std::string> adjust_pinyin_candidate_frequency(const WordItem &selected,
                                                                 const std::vector<WordItem> &ranked,
                                                                 FrequencyAdjustmentOptions options, bool force_top);

    CreatingWordProgress immediate_phrase_progress_;
    bool shuangpin_preedit_uses_raw_ = true;
    std::unique_ptr<QuanpinEngine> canonical_phrase_engine_;
    std::string pending_pinyin_sequence_;
    std::string pending_pinyin_sequence_with_cases_;
    bool has_pending_pinyin_sequence_ = false;
    bool has_pending_pinyin_sequence_with_cases_ = false;
    bool pending_wubi_literal_input_ = false;

    RuntimePaths paths_;
    CandidateQueries candidate_queries_;
    ImeSession engine_;
    // 位掩码（quanpin::kAutocorrect* 位），不是 bool：bool 会把邻键位截断丢失。
    unsigned quanpin_autocorrect_types_ = 0;
    bool quanpin_helpcode_enabled_ = true;
    bool shuangpin_helpcode_enabled_ = true;
    bool shuangpin_helpcode_direct_ = true;
    bool end_helpcode_uppercase_trigger_enabled_ = false;
    bool mid_sentence_helpcode_enabled_ = false;
    bool direct_helpcode_enabled_ = false;
    bool direct_helpcode_slash_marker_ = true;
    bool direct_helpcode_uppercase_marker_ = false;
    bool mid_sentence_uppercase_trigger_enabled_ = false;
    bool chinese_punctuation_enabled_ = true;
    bool candidate_learning_enabled_ = true;
    PunctuationPolicy punctuation_;
    const ShuangpinProfile shuangpin_profile_;
    FrequencyAdjustmentOptions frequency_adjustment_;
    bool frequency_adjustment_configured_ = false;
    LocalModeOptions local_mode_options_;
    EnglishInputOptions english_input_options_;
    MixedExpressiveOptions mixed_expressive_options_;
    bool dedicated_english_mode_ = false;
    std::string dedicated_english_preedit_;
    std::vector<WordItem> dedicated_english_candidates_;
    std::vector<WordItem> mixed_candidates_;
    LocalInputMode local_input_mode_ = LocalInputMode::None;
    std::optional<SchemeType> temporary_original_scheme_;
    std::string local_preedit_;
    std::vector<WordItem> local_candidates_;
    std::function<local_modes::LocalDateTime()> local_date_time_provider_;
    OnlineRequestGuard online_requests_;
};
} // namespace metasequoia