"use client";

import React, { useCallback, useRef, useEffect, useState } from "react";
import { Button } from "@/components/ui/button";
import { Textarea } from "@/components/ui/textarea";
import { ResetWarningModal } from "@/components/reset-warning-modal";
import { SaveDialog } from "@/components/save-dialog";
import {
    Loader2,
    Send,
    Trash2,
    Image as ImageIcon,
    History,
    Download,
} from "lucide-react";
import { toast } from "sonner";
import { ButtonWithTooltip } from "@/components/button-with-tooltip";
import { FilePreviewList } from "./file-preview-list";
import { useDiagram } from "@/contexts/diagram-context";
import { HistoryDialog } from "@/components/history-dialog";
import { ErrorToast } from "@/components/error-toast";

const MAX_FILE_SIZE = 2 * 1024 * 1024; // 2MB
const MAX_FILES = 5;

function formatFileSize(bytes: number): string {
    const mb = bytes / 1024 / 1024;
    if (mb < 0.01) return `${(bytes / 1024).toFixed(0)}KB`;
    return `${mb.toFixed(2)}MB`;
}

function showErrorToast(message: React.ReactNode) {
    toast.custom(
        (t) => <ErrorToast message={message} onDismiss={() => toast.dismiss(t)} />,
        { duration: 5000 }
    );
}

interface ValidationResult {
    validFiles: File[];
    errors: string[];
}

function validateFiles(newFiles: File[], existingCount: number): ValidationResult {
    const errors: string[] = [];
    const validFiles: File[] = [];

    const availableSlots = MAX_FILES - existingCount;

    if (availableSlots <= 0) {
        errors.push(`Maximum ${MAX_FILES} files allowed`);
        return { validFiles, errors };
    }

    for (const file of newFiles) {
        if (validFiles.length >= availableSlots) {
            errors.push(`Only ${availableSlots} more file(s) allowed`);
            break;
        }
        if (file.size > MAX_FILE_SIZE) {
            errors.push(`"${file.name}" is ${formatFileSize(file.size)} (exceeds 2MB)`);
        } else {
            validFiles.push(file);
        }
    }

    return { validFiles, errors };
}

function showValidationErrors(errors: string[]) {
    if (errors.length === 0) return;

    if (errors.length === 1) {
        showErrorToast(<span className="text-muted-foreground">{errors[0]}</span>);
    } else {
        showErrorToast(
            <div className="flex flex-col gap-1">
                <span className="font-medium">{errors.length} files rejected:</span>
                <ul className="text-muted-foreground text-xs list-disc list-inside">
                    {errors.slice(0, 3).map((err, i) => <li key={i}>{err}</li>)}
                    {errors.length > 3 && <li>...and {errors.length - 3} more</li>}
                </ul>
            </div>
        );
    }
}

interface ChatInputProps {
    input: string;
    status: "submitted" | "streaming" | "ready" | "error";
    onSubmit: (e: React.FormEvent<HTMLFormElement>) => void;
    onChange: (e: React.ChangeEvent<HTMLTextAreaElement>) => void;
    onClearChat: () => void;
    files?: File[];
    onFileChange?: (files: File[]) => void;
    showHistory?: boolean;
    onToggleHistory?: (show: boolean) => void;
    sessionId?: string;
    error?: Error | null;
}

export function ChatInput({
    input,
    status,
    onSubmit,
    onChange,
    onClearChat,
    files = [],
    onFileChange = () => {},
    showHistory = false,
    onToggleHistory = () => {},
    sessionId,
    error = null,
}: ChatInputProps) {
    const { diagramHistory, saveDiagramToFile } = useDiagram();
    const textareaRef = useRef<HTMLTextAreaElement>(null);
    const fileInputRef = useRef<HTMLInputElement>(null);
    const [isDragging, setIsDragging] = useState(false);
    const [showClearDialog, setShowClearDialog] = useState(false);
    const [showSaveDialog, setShowSaveDialog] = useState(false);

    // Allow retry when there's an error (even if status is still "streaming" or "submitted")
    const isDisabled =
        (status === "streaming" || status === "submitted") && !error;

    const adjustTextareaHeight = useCallback(() => {
        const textarea = textareaRef.current;
        if (textarea) {
            textarea.style.height = "auto";
            textarea.style.height = `${Math.min(textarea.scrollHeight, 200)}px`;
        }
    }, []);

    useEffect(() => {
        adjustTextareaHeight();
    }, [input, adjustTextareaHeight]);

    const handleKeyDown = (e: React.KeyboardEvent) => {
        if ((e.metaKey || e.ctrlKey) && e.key === "Enter") {
            e.preventDefault();
            const form = e.currentTarget.closest("form");
            if (form && input.trim() && !isDisabled) {
                form.requestSubmit();
            }
        }
    };

    const handlePaste = async (e: React.ClipboardEvent) => {
        if (isDisabled) return;

        const items = e.clipboardData.items;
        const imageItems = Array.from(items).filter((item) =>
            item.type.startsWith("image/")
        );

        if (imageItems.length > 0) {
            const imageFiles = (await Promise.all(
                imageItems.map(async (item, index) => {
                    const file = item.getAsFile();
                    if (!file) return null;
                    return new File(
                        [file],
                        `pasted-image-${Date.now()}-${index}.${file.type.split("/")[1]}`,
                        { type: file.type }
                    );
                })
            )).filter((f): f is File => f !== null);

            const { validFiles, errors } = validateFiles(imageFiles, files.length);
            showValidationErrors(errors);
            if (validFiles.length > 0) {
                onFileChange([...files, ...validFiles]);
            }
        }
    };

    const handleFileChange = (e: React.ChangeEvent<HTMLInputElement>) => {
        const newFiles = Array.from(e.target.files || []);
        const { validFiles, errors } = validateFiles(newFiles, files.length);
        showValidationErrors(errors);
        if (validFiles.length > 0) {
            onFileChange([...files, ...validFiles]);
        }
        // Reset input so same file can be selected again
        if (fileInputRef.current) {
            fileInputRef.current.value = "";
        }
    };

    const handleRemoveFile = (fileToRemove: File) => {
        onFileChange(files.filter((file) => file !== fileToRemove));
        if (fileInputRef.current) {
            fileInputRef.current.value = "";
        }
    };

    const triggerFileInput = () => {
        fileInputRef.current?.click();
    };

    const handleDragOver = (e: React.DragEvent<HTMLFormElement>) => {
        e.preventDefault();
        e.stopPropagation();
        setIsDragging(true);
    };

    const handleDragLeave = (e: React.DragEvent<HTMLFormElement>) => {
        e.preventDefault();
        e.stopPropagation();
        setIsDragging(false);
    };

    const handleDrop = (e: React.DragEvent<HTMLFormElement>) => {
        e.preventDefault();
        e.stopPropagation();
        setIsDragging(false);

        if (isDisabled) return;

        const droppedFiles = e.dataTransfer.files;
        const imageFiles = Array.from(droppedFiles).filter((file) =>
            file.type.startsWith("image/")
        );

        const { validFiles, errors } = validateFiles(imageFiles, files.length);
        showValidationErrors(errors);
        if (validFiles.length > 0) {
            onFileChange([...files, ...validFiles]);
        }
    };

    const handleClear = () => {
        onClearChat();
        setShowClearDialog(false);
    };

    return (
        <form
            onSubmit={onSubmit}
            className={`w-full transition-all duration-200 ${
                isDragging
                    ? "ring-2 ring-primary ring-offset-2 rounded-2xl"
                    : ""
            }`}
            onDragOver={handleDragOver}
            onDragLeave={handleDragLeave}
            onDrop={handleDrop}
        >
            {/* File previews */}
            {files.length > 0 && (
                <div className="mb-3">
                    <FilePreviewList
                        files={files}
                        onRemoveFile={handleRemoveFile}
                    />
                </div>
            )}

            {/* Input container */}
            <div className="relative rounded-2xl border border-border bg-background shadow-sm focus-within:ring-2 focus-within:ring-primary/20 focus-within:border-primary/50 transition-all duration-200">
                <Textarea
                    ref={textareaRef}
                    value={input}
                    onChange={onChange}
                    onKeyDown={handleKeyDown}
                    onPaste={handlePaste}
                    placeholder="Describe your diagram or paste an image..."
                    disabled={isDisabled}
                    aria-label="Chat input"
                    className="min-h-[60px] max-h-[200px] resize-none border-0 bg-transparent px-4 py-3 text-sm focus-visible:ring-0 focus-visible:ring-offset-0 placeholder:text-muted-foreground/60"
                />

                {/* Action bar */}
                <div className="flex items-center justify-between px-3 py-2 border-t border-border/50">
                    {/* Left actions */}
                    <div className="flex items-center gap-1">
                        <ButtonWithTooltip
                            type="button"
                            variant="ghost"
                            size="sm"
                            onClick={() => setShowClearDialog(true)}
                            tooltipContent="Clear conversation"
                            className="h-8 w-8 p-0 text-muted-foreground hover:text-destructive hover:bg-destructive/10"
                        >
                            <Trash2 className="h-4 w-4" />
                        </ButtonWithTooltip>

                        <ResetWarningModal
                            open={showClearDialog}
                            onOpenChange={setShowClearDialog}
                            onClear={handleClear}
                        />

                        <HistoryDialog
                            showHistory={showHistory}
                            onToggleHistory={onToggleHistory}
                        />
                    </div>

                    {/* Right actions */}
                    <div className="flex items-center gap-1">
                        <ButtonWithTooltip
                            type="button"
                            variant="ghost"
                            size="sm"
                            onClick={() => onToggleHistory(true)}
                            disabled={isDisabled || diagramHistory.length === 0}
                            tooltipContent="Diagram history"
                            className="h-8 w-8 p-0 text-muted-foreground hover:text-foreground"
                        >
                            <History className="h-4 w-4" />
                        </ButtonWithTooltip>

                        <ButtonWithTooltip
                            type="button"
                            variant="ghost"
                            size="sm"
                            onClick={() => setShowSaveDialog(true)}
                            disabled={isDisabled}
                            tooltipContent="Save diagram"
                            className="h-8 w-8 p-0 text-muted-foreground hover:text-foreground"
                        >
                            <Download className="h-4 w-4" />
                        </ButtonWithTooltip>

                        <SaveDialog
                            open={showSaveDialog}
                            onOpenChange={setShowSaveDialog}
                            onSave={(filename, format) =>
                                saveDiagramToFile(filename, format, sessionId)
                            }
                            defaultFilename={`diagram-${new Date()
                                .toISOString()
                                .slice(0, 10)}`}
                        />

                        <ButtonWithTooltip
                            type="button"
                            variant="ghost"
                            size="sm"
                            onClick={triggerFileInput}
                            disabled={isDisabled}
                            tooltipContent="Upload image"
                            className="h-8 w-8 p-0 text-muted-foreground hover:text-foreground"
                        >
                            <ImageIcon className="h-4 w-4" />
                        </ButtonWithTooltip>

                        <input
                            type="file"
                            ref={fileInputRef}
                            className="hidden"
                            onChange={handleFileChange}
                            accept="image/*"
                            multiple
                            disabled={isDisabled}
                        />

                        <div className="w-px h-5 bg-border mx-1" />

                        <Button
                            type="submit"
                            disabled={isDisabled || !input.trim()}
                            size="sm"
                            className="h-8 px-4 rounded-xl font-medium shadow-sm"
                            aria-label={
                                isDisabled ? "Sending..." : "Send message"
                            }
                        >
                            {isDisabled ? (
                                <Loader2 className="h-4 w-4 animate-spin" />
                            ) : (
                                <>
                                    <Send className="h-4 w-4 mr-1.5" />
                                    Send
                                </>
                            )}
                        </Button>
                    </div>
                </div>
            </div>
        </form>
    );
}