package com.xly.service;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import dev.langchain4j.agent.tool.ToolExecutionRequest;
import dev.langchain4j.data.message.AiMessage;
import dev.langchain4j.data.message.ChatMessage;
import dev.langchain4j.data.message.ChatMessageDeserializer;
import dev.langchain4j.data.message.SystemMessage;
import dev.langchain4j.data.message.ToolExecutionResultMessage;
import dev.langchain4j.data.message.UserMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.UnaryOperator;

/**
 * 事件账本的**唯一**投影/渲染器 —— 前端历史与 LLM 上下文同源于 {@link LedgerService} 的事件流，
 * 文案在这一处生成，不再散落在各控制器里。
 *
 * <p><b>LLM 上下文四段式</b>（{@link #project}），预算按 <b>token</b> 记账（本地保守估算
 * {@link TokenEstimator}，绝对值由 {@code llm.context-length}（镜像 Ollama 的
 * OLLAMA_CONTEXT_LENGTH，经 OpenAI 兼容通道无法逐请求传 num_ctx）导出）：
 * <ol>
 *   <li>① 稳定 system prompt + ② 进行中流程卡 —— 永不让位；</li>
 *   <li>④ 往事摘要区：预算外旧轮 → 确定性一行摘要（零模型调用）；</li>
 *   <li>⑤ 近期原文区：按**整轮**纳入，旧轮工具结果压 {@value #TOOL_DIGEST_LEN} 字；</li>
 *   <li>当前轮：原样保真、工具配对不可破坏；当前轮自身超限时**轮内让位**——最早的工具结果
 *       降为摘要（保最近 {@value #CURRENT_KEEP_FULL} 个全文），单条结果超硬顶截断。</li>
 * </ol>
 * 组装后做**发送前自检**：总 token 超预算 → ⑤ 最旧轮退入 ④、再裁 ④ 最旧行；①②与当前轮不动。
 * 绝不把超限上下文交给 Ollama 静默截头（它从最前截、① 先死）。
 */
@Service
public class EventProjectionService {

    private static final Logger log = LoggerFactory.getLogger(EventProjectionService.class);

    public static final int TOOL_DIGEST_LEN = 120;
    private static final int DIGEST_TURNS_MAX = 40;
    private static final int DIGEST_LINE_LEN = 90;

    /** 模型输出预留（num_ctx 覆盖 prompt+生成）。 */
    private static final int OUTPUT_RESERVE = 1024;
    /** 工具 schema（随每次请求发送、不在 messages 里）的估算开销。 */
    private static final int TOOLS_OVERHEAD = 2000;
    /** 当前轮增长的乐观小额预留（每次工具往返都会重投影，超出时反应式收缩⑤）。 */
    private static final int TURN_RESERVE = 512;
    /** ④ 摘要区 token 上限。 */
    private static final int DIGEST_BUDGET = 800;
    /** 当前轮里保全文的最近工具结果个数（轮内让位时更早的降摘要）。 */
    private static final int CURRENT_KEEP_FULL = 2;
    /** 当前轮单条工具结果硬顶（token），超出截断。 */
    private static final int SINGLE_RESULT_CAP = 2400;

    private final ObjectMapper mapper;
    private final int contextLength;

    /** opId → 人类可读状态行（Phase C：流程卡只读展示 ai_op_queue.sStatus）。可空（测试/未装配）。 */
    private volatile UnaryOperator<String> opStatusLookup;

    public EventProjectionService(ObjectMapper mapper, @Value("${llm.context-length:16384}") int contextLength) {
        this.mapper = mapper;
        this.contextLength = contextLength;
    }

    public EventProjectionService(ObjectMapper mapper) {
        this(mapper, 16384);
    }

    public void setOpStatusLookup(UnaryOperator<String> lookup) {
        this.opStatusLookup = lookup;
    }

    /** 输入 prompt 的总预算（token）。 */
    int promptBudget() {
        return Math.max(2048, contextLength - OUTPUT_RESERVE - TOOLS_OVERHEAD);
    }

    // ---------------------------------------------------------------- LLM 投影

    /** 四段式 LLM 上下文（token 记账）。systemText 为空时不出 system 消息（如测试）。 */
    public List<ChatMessage> project(String systemText, List<Map<String, Object>> events) {
        int budget = promptBudget();
        List<List<Map<String, Object>>> turns = groupTurns(events);
        int current = turns.size() - 1;

        // ①② system + 流程卡（永不让位）
        SystemMessage sys = null;
        int sysEst = 0;
        if (systemText != null && !systemText.isBlank()) {
            String card = activeCard(events);
            sys = SystemMessage.from(card == null ? systemText
                    : systemText + "\n\n【进行中的流程】\n" + card);
            sysEst = TokenEstimator.estimate(sys);
        }

        // 当前轮：原样保真；自身超限时轮内让位
        List<ChatMessage> currentMsgs = new ArrayList<>();
        int curEst = 0;
        if (current >= 0) {
            int curAllowance = budget - sysEst - TURN_RESERVE;
            currentMsgs = renderCurrentTurn(turns.get(current), curAllowance);
            curEst = TokenEstimator.estimate(currentMsgs);
        }

        // ⑤ 近期原文区：从最新旧轮往回按整轮纳入
        List<List<ChatMessage>> oldRendered = new ArrayList<>(); // index 对齐 turns[0..current-1]
        int[] oldEst = new int[Math.max(0, current)];
        for (int i = 0; i < current; i++) {
            List<ChatMessage> ms = new ArrayList<>();
            appendTurnMessages(ms, turns.get(i), false);
            oldRendered.add(ms);
            oldEst[i] = TokenEstimator.estimate(ms);
        }
        int remaining = budget - sysEst - curEst - TURN_RESERVE;
        int firstVerbatim = fillRecent(oldEst, current, remaining, 0);
        if (firstVerbatim > 0) { // 有轮进摘要区 → 给 ④ 留预算后重算
            firstVerbatim = fillRecent(oldEst, current, remaining, DIGEST_BUDGET);
        }

        // ④ 摘要行
        List<String> digestLines = new ArrayList<>();
        int digestFrom = Math.max(0, firstVerbatim - DIGEST_TURNS_MAX);
        for (int i = digestFrom; i < firstVerbatim; i++) {
            String line = digestLine(turns.get(i));
            if (!line.isBlank()) {
                digestLines.add(line);
            }
        }
        int omitted = digestFrom;

        // 组装 + 发送前自检（⑤ 最旧退 ④ → 裁 ④ 最旧；①② 与当前轮不动）
        while (true) {
            List<ChatMessage> out = assemble(sys, digestLines, omitted, oldRendered, firstVerbatim, current, currentMsgs);
            int total = TokenEstimator.estimate(out);
            if (total <= budget) {
                return out;
            }
            if (firstVerbatim < current) {
                String line = digestLine(turns.get(firstVerbatim));
                if (!line.isBlank()) {
                    digestLines.add(line);
                }
                firstVerbatim++;
                continue;
            }
            if (!digestLines.isEmpty()) {
                digestLines.remove(0);
                omitted++;
                continue;
            }
            log.warn("projection over budget even after shrink: total≈{}t budget={}t (当前轮过大)", total, budget);
            return out;
        }
    }

    /** ⑤ 从最新旧轮往回装，返回 firstVerbatim（第一条进原文区的旧轮下标；current 表示一条都装不下）。 */
    private static int fillRecent(int[] oldEst, int current, int remaining, int digestAllowance) {
        int budget = remaining - digestAllowance;
        int used = 0;
        int first = current;
        for (int i = current - 1; i >= 0; i--) {
            if (used + oldEst[i] > budget) {
                break;
            }
            used += oldEst[i];
            first = i;
        }
        return first;
    }

    private List<ChatMessage> assemble(SystemMessage sys, List<String> digestLines, int omitted,
                                       List<List<ChatMessage>> oldRendered, int firstVerbatim, int current,
                                       List<ChatMessage> currentMsgs) {
        List<ChatMessage> out = new ArrayList<>();
        if (sys != null) {
            out.add(sys);
        }
        if (!digestLines.isEmpty() || omitted > 0) {
            StringBuilder sb = new StringBuilder("【更早对话摘要（自动截断，仅供参考）】");
            if (omitted > 0) {
                sb.append("\n（更早 ").append(omitted).append(" 轮已省略）");
            }
            for (String line : digestLines) {
                sb.append("\n- ").append(line);
            }
            out.add(UserMessage.from(sb.toString()));
        }
        for (int i = firstVerbatim; i < current; i++) {
            out.addAll(oldRendered.get(i));
        }
        out.addAll(currentMsgs);
        return out;
    }

    /**
     * 当前轮渲染：原样保真；总量超 allowance 时**轮内让位**——最早的工具结果先降
     * {@value #TOOL_DIGEST_LEN} 字摘要（保最近 {@value #CURRENT_KEEP_FULL} 个全文，仍超则只保 1 个）。
     * 工具调用/结果配对永不破坏，单条结果超 {@value #SINGLE_RESULT_CAP}t 截断。
     */
    private List<ChatMessage> renderCurrentTurn(List<Map<String, Object>> turn, int allowance) {
        for (int keepFull = CURRENT_KEEP_FULL; keepFull >= 0; keepFull--) {
            List<ChatMessage> ms = renderCurrentWith(turn, keepFull);
            if (TokenEstimator.estimate(ms) <= allowance || keepFull == 0) {
                return ms;
            }
        }
        return List.of();
    }

    private List<ChatMessage> renderCurrentWith(List<Map<String, Object>> turn, int keepFull) {
        int results = 0;
        for (Map<String, Object> ev : turn) {
            if ("tool_result".equals(str(ev.get("type")))) {
                results++;
            }
        }
        int demote = Math.max(0, results - keepFull);
        List<ChatMessage> out = new ArrayList<>();
        int seen = 0;
        for (Map<String, Object> ev : turn) {
            if ("tool_result".equals(str(ev.get("type")))) {
                seen++;
                String text = seen <= demote ? str(ev.get("digest")) : capped(str(ev.get("text")));
                out.add(ToolExecutionResultMessage.from(str(ev.get("tcId")), str(ev.get("name")), text));
            } else {
                appendOneMessage(out, ev, true);
            }
        }
        return out;
    }

    private static String capped(String text) {
        if (TokenEstimator.estimate(text) <= SINGLE_RESULT_CAP) {
            return text;
        }
        // 按估算规则回推一个安全字符数（全 CJK 最坏情形 = 1 字 1 token）
        return text.substring(0, Math.min(text.length(), SINGLE_RESULT_CAP)) + "……[超长已截断]";
    }

    /** 一轮 → LLM 消息。当前轮工具结果全文保真；旧轮压一行摘要。 */
    private void appendTurnMessages(List<ChatMessage> out, List<Map<String, Object>> turn, boolean isCurrent) {
        for (Map<String, Object> ev : turn) {
            if ("tool_result".equals(str(ev.get("type")))) {
                String text = isCurrent ? str(ev.get("text")) : str(ev.get("digest"));
                out.add(ToolExecutionResultMessage.from(str(ev.get("tcId")), str(ev.get("name")), text));
            } else {
                appendOneMessage(out, ev, isCurrent);
            }
        }
    }

    private void appendOneMessage(List<ChatMessage> out, Map<String, Object> ev, boolean isCurrent) {
        String type = str(ev.get("type"));
        switch (type) {
            case "user" -> out.add(UserMessage.from(str(ev.get("text"))));
            case "form_submit" -> out.add(UserMessage.from(renderFormSubmit(ev)));
            case "ai", "assistant", "clarify" -> addAi(out, str(ev.get("text")));
            case "tool_call" -> {
                ChatMessage m = toolCallMessage(ev);
                if (m != null) {
                    out.add(m);
                }
            }
            case "question" -> addAi(out, str(ev.get("question")));
            case "form" -> addAi(out, "已为「" + str(ev.get("entity")) + "」弹出新建表单，等待用户填写提交。");
            case "queued" -> addAi(out, renderQueued(ev));
            case "proposal" -> addAi(out, "已生成待确认提议：" + str(ev.get("summary")) + "（等待用户点确认/取消，尚未执行）");
            case "confirm", "cancel" -> addAi(out, renderOutcome(ev));
            default -> { } // tool(旧版摘要)/skill_active/skill_done 不进正文（skill 由流程卡承载）
        }
    }

    /** tool_call 事件 → AiMessage：优先中立格式 calls=[{id,name,args}]，回退旧版 LangChain4j 序列化载荷。 */
    private ChatMessage toolCallMessage(Map<String, Object> ev) {
        Object calls = ev.get("calls");
        if (calls instanceof List<?> list && !list.isEmpty()) {
            List<ToolExecutionRequest> reqs = new ArrayList<>();
            for (Object o : list) {
                if (o instanceof Map<?, ?> m) {
                    reqs.add(ToolExecutionRequest.builder()
                            .id(str(m.get("id")))
                            .name(str(m.get("name")))
                            .arguments(str(m.get("args")))
                            .build());
                }
            }
            if (!reqs.isEmpty()) {
                String text = str(ev.get("text"));
                return text.isBlank() ? AiMessage.from(reqs) : AiMessage.from(text, reqs);
            }
        }
        return fromPayload(str(ev.get("payload")));
    }

    // ---------------------------------------------------------------- 前端历史投影

    /** 前端历史（API 形状不变：{role:user|ai, content}）。internal 用户事件（护栏重试话术）不显示。 */
    public List<Map<String, String>> historyView(List<Map<String, Object>> events) {
        List<Map<String, String>> out = new ArrayList<>();
        for (Map<String, Object> ev : events) {
            String type = str(ev.get("type"));
            switch (type) {
                case "user" -> {
                    if (!Boolean.TRUE.equals(ev.get("internal"))) {
                        out.add(Map.of("role", "user", "content", str(ev.get("text"))));
                    }
                }
                case "form_submit" -> out.add(Map.of("role", "user", "content", renderFormSubmit(ev)));
                case "ai", "assistant", "clarify" -> addHist(out, str(ev.get("text")));
                case "question" -> addHist(out, str(ev.get("question")));
                case "form" -> addHist(out, "【表单】新建" + str(ev.get("entity")) + "：" + str(ev.get("message")));
                case "queued" -> addHist(out, "【已提交待办】" + str(ev.get("description")));
                case "proposal" -> addHist(out, "【待确认】" + str(ev.get("summary")));
                case "confirm" -> addHist(out, ("executed".equals(str(ev.get("status"))) ? "【已执行】" : "【执行失败】")
                        + str(ev.get("description")) + parenOr(str(ev.get("msg"))));
                case "cancel" -> addHist(out, "【已取消】" + str(ev.get("description")));
                case "tool_result" -> addHist(out, historyFromToolResult(ev));
                default -> { }
            }
        }
        return out;
    }

    /** agent 路径的 提问/表单/预览 不再单独落显示事件——从工具结果同源推导。 */
    private String historyFromToolResult(Map<String, Object> ev) {
        String name = str(ev.get("name"));
        if (!"askUser".equals(name) && !"collectForm".equals(name)
                && !"previewChange".equals(name) && !"proposeWrite".equals(name)) {
            return "";
        }
        try {
            JsonNode r = mapper.readTree(str(ev.get("text")));
            if ("askUser".equals(name) && "question".equals(r.path("type").asText(""))) {
                return r.path("question").asText("");
            }
            if ("collectForm".equals(name) && "form_collect".equals(r.path("type").asText(""))) {
                return "【表单】新建" + r.path("entity").asText("") + "：" + r.path("message").asText("");
            }
            if ("previewChange".equals(name) && "change_preview".equals(r.path("type").asText(""))) {
                return "【预览】" + r.path("summary").asText("");
            }
            if ("proposeWrite".equals(name) && !r.path("opId").asText("").isBlank()) {
                return "【待确认】" + r.path("summary").asText("");
            }
        } catch (Exception ignore) {
        }
        return "";
    }

    // ---------------------------------------------------------------- 流程卡（② 段）

    /**
     * 进行中流程卡：激活 skill 全文（最近一次 {@code skill_active}，被 {@code skill_done} 或更新的
     * skill 覆盖前一直钉住）+ 在办单据状态（表单待提交 / 预览待保存 / 已提交待办的只读进度）。
     * {@code queued} 后技能线摘下（AI 侧流程到写入队列为止），待办行保留到下一个流程事件替换。
     * 两者皆无 → null。
     */
    public String activeCard(List<Map<String, Object>> events) {
        String skillText = null;
        Map<String, Object> lastFlow = null;

        for (Map<String, Object> ev : events) {
            String type = str(ev.get("type"));
            switch (type) {
                case "skill_active" -> skillText = str(ev.get("text"));
                case "skill_done" -> skillText = null;
                case "form", "form_submit", "proposal" -> lastFlow = ev;
                case "queued", "confirm", "cancel" -> { // AI 侧流程终结：技能线摘下
                    lastFlow = ev;
                    skillText = null;
                }
                case "tool_result" -> {
                    Map<String, Object> derived = deriveFlowEvent(ev);
                    if (derived != null) {
                        lastFlow = derived;
                    }
                }
                default -> { }
            }
        }

        String docLine = null;
        if (lastFlow != null) {
            switch (str(lastFlow.get("type"))) {
                case "form" -> docLine = "已为「" + str(lastFlow.get("entity")) + "」弹出新建表单，等待用户填写提交。";
                case "preview" -> docLine = "已生成写操作预览卡：" + str(lastFlow.get("summary"))
                        + "（等待用户点卡上按钮提交，**尚未写入**）。";
                case "queued" -> docLine = renderQueuedLine(lastFlow);
                case "proposal" -> docLine = "待确认提议：" + str(lastFlow.get("summary"))
                        + "（opId=" + str(lastFlow.get("opId")) + "，用户点【确认】才会执行）。";
                default -> { } // form_submit/confirm/cancel = 流程已推进/终结
            }
        }

        if (skillText == null && docLine == null) {
            return null;
        }
        StringBuilder sb = new StringBuilder();
        if (skillText != null) {
            sb.append(skillText);
        }
        if (docLine != null) {
            if (sb.length() > 0) {
                sb.append("\n");
            }
            sb.append("在办单据：").append(docLine);
        }
        return sb.toString();
    }

    /** 工具结果 → 流程事件（collectForm 弹表单 / previewChange 出预览 / 旧版 proposeWrite），供流程卡推导。 */
    private Map<String, Object> deriveFlowEvent(Map<String, Object> ev) {
        String name = str(ev.get("name"));
        if (!"collectForm".equals(name) && !"previewChange".equals(name) && !"proposeWrite".equals(name)) {
            return null;
        }
        try {
            JsonNode r = mapper.readTree(str(ev.get("text")));
            if ("collectForm".equals(name) && "form_collect".equals(r.path("type").asText(""))) {
                Map<String, Object> m = new LinkedHashMap<>();
                m.put("type", "form");
                m.put("entity", r.path("entity").asText(""));
                return m;
            }
            if ("previewChange".equals(name) && "change_preview".equals(r.path("type").asText(""))) {
                Map<String, Object> m = new LinkedHashMap<>();
                m.put("type", "preview");
                m.put("previewId", r.path("previewId").asText(""));
                m.put("summary", r.path("summary").asText(""));
                return m;
            }
            if ("proposeWrite".equals(name) && !r.path("opId").asText("").isBlank()) {
                Map<String, Object> m = new LinkedHashMap<>();
                m.put("type", "proposal");
                m.put("opId", r.path("opId").asText(""));
                m.put("summary", r.path("summary").asText(""));
                return m;
            }
        } catch (Exception ignore) {
        }
        return null;
    }

    // ---------------------------------------------------------------- 内部

    /** 按用户事件（user/form_submit）分轮；轮前遗留事件并入首轮。 */
    private static List<List<Map<String, Object>>> groupTurns(List<Map<String, Object>> events) {
        List<List<Map<String, Object>>> turns = new ArrayList<>();
        List<Map<String, Object>> cur = new ArrayList<>();
        for (Map<String, Object> ev : events) {
            String type = str(ev.get("type"));
            if (("user".equals(type) || "form_submit".equals(type)) && !cur.isEmpty()) {
                turns.add(cur);
                cur = new ArrayList<>();
            }
            cur.add(ev);
        }
        if (!cur.isEmpty()) {
            turns.add(cur);
        }
        return turns;
    }

    /** 一轮 → 一行确定性摘要：用户说了什么 ⇒ 结果是什么。 */
    private String digestLine(List<Map<String, Object>> turn) {
        String userText = "";
        String outcome = "";
        for (Map<String, Object> ev : turn) {
            String type = str(ev.get("type"));
            switch (type) {
                case "user" -> userText = str(ev.get("text"));
                case "form_submit" -> userText = renderFormSubmit(ev);
                case "ai", "assistant", "clarify" -> outcome = str(ev.get("text"));
                case "question" -> outcome = "问：" + str(ev.get("question"));
                case "form" -> outcome = "弹出「" + str(ev.get("entity")) + "」新建表单";
                case "queued" -> outcome = "已提交待办：" + str(ev.get("description"));
                case "proposal" -> outcome = "生成待确认提议：" + str(ev.get("summary"));
                case "confirm" -> outcome = ("executed".equals(str(ev.get("status"))) ? "用户确认，执行成功：" : "确认后执行失败：")
                        + str(ev.get("description"));
                case "cancel" -> outcome = "用户取消：" + str(ev.get("description"));
                case "tool_result" -> {
                    String h = historyFromToolResult(ev);
                    if (!h.isBlank()) {
                        outcome = h;
                    }
                }
                default -> { }
            }
        }
        if (userText.isBlank() && outcome.isBlank()) {
            return "";
        }
        return clip(userText, 40) + (outcome.isBlank() ? "" : " ⇒ " + clip(outcome, DIGEST_LINE_LEN));
    }

    private ChatMessage fromPayload(String payload) {
        try {
            List<ChatMessage> ms = ChatMessageDeserializer.messagesFromJson(payload);
            return ms.isEmpty() ? null : ms.get(0);
        } catch (Exception e) {
            return null;
        }
    }

    private String renderFormSubmit(Map<String, Object> ev) {
        return "提交「" + str(ev.get("entity")) + "」新增表单：" + str(ev.get("fields"));
    }

    private String renderQueued(Map<String, Object> ev) {
        return "（系统）用户已保存，操作已提交待办：" + str(ev.get("description"))
                + "（AI 侧流程到此为止，是否/何时执行由 ERP 处理；绝不声称已执行成功）";
    }

    /** queued 流程卡行：附 ai_op_queue.sStatus 只读进度（可用时）。 */
    private String renderQueuedLine(Map<String, Object> ev) {
        String desc = str(ev.get("description"));
        String status = null;
        UnaryOperator<String> lookup = opStatusLookup;
        Object opIds = ev.get("opIds");
        if (lookup != null && opIds instanceof List<?> ids && !ids.isEmpty()) {
            try {
                status = lookup.apply(String.valueOf(ids.get(0)));
            } catch (Exception ignore) {
            }
        }
        return "已提交待办：" + desc + "（当前状态：" + (status == null || status.isBlank() ? "等待 ERP 处理" : status)
                + "；只读进度，勿再重复提交）。";
    }

    private String renderOutcome(Map<String, Object> ev) {
        String desc = str(ev.get("description"));
        if ("cancel".equals(str(ev.get("type")))) {
            return "（系统）用户取消了该操作：" + desc;
        }
        if ("executed".equals(str(ev.get("status")))) {
            return "（系统）用户已确认，操作执行成功：" + desc;
        }
        String msg = str(ev.get("msg"));
        return "（系统）用户确认后执行失败：" + desc + (msg.isBlank() ? "" : "，原因：" + msg);
    }

    private static void addAi(List<ChatMessage> out, String text) {
        if (text != null && !text.isBlank()) {
            out.add(AiMessage.from(text));
        }
    }

    private static void addHist(List<Map<String, String>> out, String text) {
        if (text != null && !text.isBlank()) {
            out.add(Map.of("role", "ai", "content", text));
        }
    }

    private static String clip(String s, int max) {
        String t = s == null ? "" : s.replace('\n', ' ').trim();
        return t.length() > max ? t.substring(0, max) + "…" : t;
    }

    private static String parenOr(String msg) {
        return msg == null || msg.isBlank() ? "" : ("（" + msg + "）");
    }

    private static String str(Object o) {
        return o == null ? "" : o.toString();
    }
}