"use client";

import { useEffect, useState, useCallback, useRef } from "react";
import { CodeBlock } from "./code-block";

const SIMULATION_PROMPT = "Create a contact form with name, email, and message";

interface UIElement {
  key: string;
  type: string;
  props: Record<string, unknown>;
  children?: string[];
}

interface UITree {
  root: string;
  elements: Record<string, UIElement>;
}

interface SimulationStage {
  tree: UITree;
  stream: string;
}

const SIMULATION_STAGES: SimulationStage[] = [
  {
    tree: { root: "form", elements: { form: { key: "form", type: "Form", props: { title: "Contact Us" }, children: [] } } },
    stream: '{"op":"set","path":"/root","value":"form"}',
  },
  {
    tree: { root: "form", elements: { form: { key: "form", type: "Form", props: { title: "Contact Us" }, children: ["name"] }, name: { key: "name", type: "Input", props: { label: "Name", name: "name" } } } },
    stream: '{"op":"add","path":"/elements/form","value":{"key":"form","type":"Form","props":{"title":"Contact Us"},"children":["name"]}}',
  },
  {
    tree: { root: "form", elements: { form: { key: "form", type: "Form", props: { title: "Contact Us" }, children: ["name", "email"] }, name: { key: "name", type: "Input", props: { label: "Name", name: "name" } }, email: { key: "email", type: "Input", props: { label: "Email", name: "email" } } } },
    stream: '{"op":"add","path":"/elements/email","value":{"key":"email","type":"Input","props":{"label":"Email","name":"email"}}}',
  },
  {
    tree: { root: "form", elements: { form: { key: "form", type: "Form", props: { title: "Contact Us" }, children: ["name", "email", "message"] }, name: { key: "name", type: "Input", props: { label: "Name", name: "name" } }, email: { key: "email", type: "Input", props: { label: "Email", name: "email" } }, message: { key: "message", type: "Textarea", props: { label: "Message", name: "message" } } } },
    stream: '{"op":"add","path":"/elements/message","value":{"key":"message","type":"Textarea","props":{"label":"Message","name":"message"}}}',
  },
  {
    tree: { root: "form", elements: { form: { key: "form", type: "Form", props: { title: "Contact Us" }, children: ["name", "email", "message", "submit"] }, name: { key: "name", type: "Input", props: { label: "Name", name: "name" } }, email: { key: "email", type: "Input", props: { label: "Email", name: "email" } }, message: { key: "message", type: "Textarea", props: { label: "Message", name: "message" } }, submit: { key: "submit", type: "Button", props: { label: "Send Message", action: "submit" } } } },
    stream: '{"op":"add","path":"/elements/submit","value":{"key":"submit","type":"Button","props":{"label":"Send Message","action":"submit"}}}',
  },
];

const CODE_EXAMPLE = `import { createCatalog } from '@json-render/core';
import { z } from 'zod';

export const catalog = createCatalog({
  components: {
    Form: {
      props: z.object({
        title: z.string(),
      }),
      hasChildren: true,
    },
    Input: {
      props: z.object({
        label: z.string(),
        name: z.string(),
      }),
    },
    Textarea: {
      props: z.object({
        label: z.string(),
        name: z.string(),
      }),
    },
    Button: {
      props: z.object({
        label: z.string(),
        action: z.string(),
      }),
    },
  },
});`;

type Mode = "simulation" | "interactive";
type Phase = "typing" | "streaming" | "complete";
type Tab = "stream" | "json" | "code";

function parsePatch(line: string): { op: string; path: string; value: unknown } | null {
  try {
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith("//")) return null;
    return JSON.parse(trimmed);
  } catch {
    return null;
  }
}

function applyPatch(tree: UITree, patch: { op: string; path: string; value: unknown }): UITree {
  const newTree = { ...tree, elements: { ...tree.elements } };

  if (patch.path === "/root") {
    newTree.root = patch.value as string;
    return newTree;
  }

  if (patch.path.startsWith("/elements/")) {
    const key = patch.path.slice("/elements/".length).split("/")[0];
    if (key && (patch.op === "set" || patch.op === "add")) {
      newTree.elements[key] = patch.value as UIElement;
    }
  }

  return newTree;
}

export function Demo() {
  const [mode, setMode] = useState<Mode>("simulation");
  const [phase, setPhase] = useState<Phase>("typing");
  const [typedPrompt, setTypedPrompt] = useState("");
  const [userPrompt, setUserPrompt] = useState("");
  const [stageIndex, setStageIndex] = useState(-1);
  const [streamLines, setStreamLines] = useState<string[]>([]);
  const [activeTab, setActiveTab] = useState<Tab>("json");
  const [actionFired, setActionFired] = useState(false);
  const [tree, setTree] = useState<UITree | null>(null);
  const [isLoading, setIsLoading] = useState(false);
  const abortRef = useRef<AbortController | null>(null);

  const currentSimulationStage = stageIndex >= 0 ? SIMULATION_STAGES[stageIndex] : null;

  const stopGeneration = useCallback(() => {
    abortRef.current?.abort();
    if (mode === "simulation") {
      // Skip to interactive mode
      setMode("interactive");
      setPhase("complete");
      setTypedPrompt(SIMULATION_PROMPT);
      setUserPrompt("");
    }
    setIsLoading(false);
  }, [mode]);

  // Typing effect for simulation
  useEffect(() => {
    if (mode !== "simulation" || phase !== "typing") return;

    let i = 0;
    const interval = setInterval(() => {
      if (i < SIMULATION_PROMPT.length) {
        setTypedPrompt(SIMULATION_PROMPT.slice(0, i + 1));
        i++;
      } else {
        clearInterval(interval);
        setTimeout(() => setPhase("streaming"), 500);
      }
    }, 20);

    return () => clearInterval(interval);
  }, [mode, phase]);

  // Streaming effect for simulation
  useEffect(() => {
    if (mode !== "simulation" || phase !== "streaming") return;

    let i = 0;
    const interval = setInterval(() => {
      if (i < SIMULATION_STAGES.length) {
        const stage = SIMULATION_STAGES[i];
        if (stage) {
          setStageIndex(i);
          setStreamLines((prev) => [...prev, stage.stream]);
          setTree(stage.tree);
        }
        i++;
      } else {
        clearInterval(interval);
        setTimeout(() => {
          setPhase("complete");
          setMode("interactive");
          setUserPrompt("");
        }, 500);
      }
    }, 600);

    return () => clearInterval(interval);
  }, [mode, phase]);

  const handleSubmit = useCallback(async () => {
    if (!userPrompt.trim() || isLoading) return;

    abortRef.current?.abort();
    abortRef.current = new AbortController();

    setIsLoading(true);
    setStreamLines([]);
    setTree({ root: "", elements: {} });

    try {
      const response = await fetch("/api/generate", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ prompt: userPrompt }),
        signal: abortRef.current.signal,
      });

      if (!response.ok) throw new Error(`HTTP error: ${response.status}`);

      const reader = response.body?.getReader();
      if (!reader) throw new Error("No response body");

      const decoder = new TextDecoder();
      let buffer = "";
      let currentTree: UITree = { root: "", elements: {} };

      while (true) {
        const { done, value } = await reader.read();
        if (done) break;

        buffer += decoder.decode(value, { stream: true });
        const lines = buffer.split("\n");
        buffer = lines.pop() ?? "";

        for (const line of lines) {
          const patch = parsePatch(line);
          if (patch) {
            currentTree = applyPatch(currentTree, patch);
            setTree({ ...currentTree });
            setStreamLines((prev) => [...prev, line.trim()]);
          }
        }
      }

      if (buffer.trim()) {
        const patch = parsePatch(buffer);
        if (patch) {
          currentTree = applyPatch(currentTree, patch);
          setTree({ ...currentTree });
          setStreamLines((prev) => [...prev, buffer.trim()]);
        }
      }
    } catch (err) {
      if ((err as Error).name !== "AbortError") {
        console.error("Generation error:", err);
      }
    } finally {
      setIsLoading(false);
    }
  }, [userPrompt, isLoading]);

  const handleAction = () => {
    setActionFired(true);
    setTimeout(() => setActionFired(false), 2000);
  };

  // Render preview from tree
  const renderPreview = () => {
    const currentTree = mode === "simulation" ? currentSimulationStage?.tree : tree;

    if (!currentTree || !currentTree.root || !currentTree.elements[currentTree.root]) {
      return <div className="text-muted-foreground/50 text-sm">{isLoading ? "generating..." : "waiting..."}</div>;
    }

    const root = currentTree.elements[currentTree.root];
    if (!root) return null;

    const title = root.props.title as string | undefined;
    const children = (root.children ?? []).map((key) => currentTree.elements[key]).filter(Boolean) as UIElement[];

    return (
      <div className="text-center animate-in fade-in duration-200">
        <div className="border border-border rounded-lg p-4 bg-background inline-block text-left w-56">
          {title && <h3 className="font-semibold mb-3 text-sm">{title}</h3>}
          <div className="space-y-2">
            {children.map((child) => {
              if (child.type === "Input") {
                return (
                  <div key={child.key} className="animate-in fade-in slide-in-from-bottom-1 duration-200">
                    <label className="text-[10px] text-muted-foreground block mb-0.5">
                      {child.props.label as string}
                    </label>
                    <div className="h-7 w-full bg-card border border-border rounded px-2 text-xs" />
                  </div>
                );
              }
              if (child.type === "Textarea") {
                return (
                  <div key={child.key} className="animate-in fade-in slide-in-from-bottom-1 duration-200">
                    <label className="text-[10px] text-muted-foreground block mb-0.5">
                      {child.props.label as string}
                    </label>
                    <div className="h-14 w-full bg-card border border-border rounded px-2 text-xs" />
                  </div>
                );
              }
              if (child.type === "Button") {
                return (
                  <button
                    key={child.key}
                    onClick={handleAction}
                    className="w-full px-3 py-1.5 bg-foreground text-background rounded text-xs font-medium hover:opacity-90 transition-opacity animate-in fade-in slide-in-from-bottom-1 duration-200"
                  >
                    {child.props.label as string}
                  </button>
                );
              }
              return null;
            })}
          </div>
        </div>
        {actionFired && (
          <div className="mt-3 text-xs font-mono text-muted-foreground animate-in fade-in slide-in-from-bottom-2">
            onAction(&quot;submit&quot;)
          </div>
        )}
      </div>
    );
  };

  const currentTree = mode === "simulation" ? currentSimulationStage?.tree : tree;
  const jsonCode = currentTree ? JSON.stringify(currentTree, null, 2) : "// waiting...";

  const isTypingSimulation = mode === "simulation" && phase === "typing";
  const isStreamingSimulation = mode === "simulation" && phase === "streaming";
  const showLoadingDots = isStreamingSimulation || isLoading;

  return (
    <div className="w-full max-w-4xl mx-auto">
      {/* Prompt input */}
      <div className="mb-6">
        <div className="border border-border rounded p-3 bg-card font-mono text-sm min-h-[44px] flex items-center justify-between">
          {mode === "simulation" ? (
            <div className="flex items-center flex-1">
              <span className="inline-flex items-center h-5">{typedPrompt}</span>
              {isTypingSimulation && (
                <span className="inline-block w-2 h-4 bg-foreground ml-0.5 animate-pulse" />
              )}
            </div>
          ) : (
            <form
              className="flex items-center flex-1"
              onSubmit={(e) => {
                e.preventDefault();
                handleSubmit();
              }}
            >
              <input
                type="text"
                value={userPrompt}
                onChange={(e) => setUserPrompt(e.target.value)}
                placeholder="Describe what you want to build..."
                className="flex-1 bg-transparent outline-none placeholder:text-muted-foreground/50"
                disabled={isLoading}
                maxLength={140}
                autoFocus
              />
            </form>
          )}
          {(mode === "simulation" || isLoading) ? (
            <button
              onClick={stopGeneration}
              className="ml-2 p-1 text-muted-foreground hover:text-foreground transition-colors"
              aria-label="Stop"
            >
              <svg
                width="14"
                height="14"
                viewBox="0 0 24 24"
                fill="currentColor"
                stroke="none"
              >
                <rect x="6" y="6" width="12" height="12" rx="1" />
              </svg>
            </button>
          ) : (
            <button
              onClick={handleSubmit}
              disabled={!userPrompt.trim()}
              className="ml-2 p-1 text-muted-foreground hover:text-foreground transition-colors disabled:opacity-30"
              aria-label="Submit"
            >
              <svg
                width="14"
                height="14"
                viewBox="0 0 24 24"
                fill="none"
                stroke="currentColor"
                strokeWidth="2"
                strokeLinecap="round"
                strokeLinejoin="round"
              >
                <path d="M12 5v14" />
                <path d="M19 12l-7 7-7-7" />
              </svg>
            </button>
          )}
        </div>
        <div className="mt-2 text-xs text-muted-foreground">
          Try: &quot;Create a login form&quot; or &quot;Build a feedback form with rating&quot;
        </div>
      </div>

      <div className="grid lg:grid-cols-2 gap-4">
        {/* Tabbed code/stream/json panel */}
        <div>
          <div className="flex gap-4 mb-2">
            {(["json", "stream", "code"] as const).map((tab) => (
              <button
                key={tab}
                onClick={() => setActiveTab(tab)}
                className={`text-xs font-mono transition-colors ${
                  activeTab === tab ? "text-foreground" : "text-muted-foreground hover:text-foreground"
                }`}
              >
                {tab}
              </button>
            ))}
          </div>
          <div className="border border-border rounded p-3 bg-card font-mono text-xs h-96 overflow-auto text-left">
            {activeTab === "stream" && (
              <div className="space-y-1">
                {streamLines.map((line, i) => (
                  <div
                    key={i}
                    className="text-muted-foreground truncate animate-in fade-in slide-in-from-bottom-1 duration-200"
                  >
                    {line}
                  </div>
                ))}
                {showLoadingDots && (
                  <div className="flex gap-1 mt-2">
                    <span className="w-1 h-1 bg-muted-foreground rounded-full animate-pulse" />
                    <span className="w-1 h-1 bg-muted-foreground rounded-full animate-pulse [animation-delay:75ms]" />
                    <span className="w-1 h-1 bg-muted-foreground rounded-full animate-pulse [animation-delay:150ms]" />
                  </div>
                )}
                {streamLines.length === 0 && !showLoadingDots && (
                  <div className="text-muted-foreground/50">waiting...</div>
                )}
              </div>
            )}
            <div className={activeTab === "json" ? "" : "hidden"}>
              <CodeBlock code={jsonCode} lang="json" />
            </div>
            <div className={activeTab === "code" ? "" : "hidden"}>
              <CodeBlock code={CODE_EXAMPLE} lang="tsx" />
            </div>
          </div>
        </div>

        {/* Rendered output */}
        <div>
          <div className="text-xs text-muted-foreground mb-2 font-mono">render</div>
          <div className="border border-border rounded p-3 bg-card h-96 flex items-center justify-center">
            {renderPreview()}
          </div>
        </div>
      </div>
    </div>
  );
}