import React, { useState, useEffect } from "react";
import { useNavigate, useParams } from "react-router-dom";
import { ArrowLeft, Loader2 } from "lucide-react";
import { useForm } from "react-hook-form";
import Layout from "@/components/layout/layout";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Textarea } from "@/components/ui/textarea";
import {
  Card,
  CardContent,
  CardDescription,
  CardHeader,
  CardTitle,
} from "@/components/ui/card";
import {
  Form,
  FormControl,
  FormField,
  FormItem,
  FormLabel,
  FormMessage,
} from "@/components/ui/form";
import { toast } from "@/lib/custom-toast";
import { issuesApi, projectService, deliverablesApi, employeeService } from "@/lib/api";
import { IssueUpdateRequest, IssueApi, ProjectApi, Deliverable, Employee } from "@/types";
import { Dropdown, DropdownOption } from "@/components/ui/dropdown";

const IssueEdit = () => {
  const { id } = useParams<{ id: string }>();
  const navigate = useNavigate();
  const [isSubmitting, setIsSubmitting] = useState(false);
  const [isLoading, setIsLoading] = useState(true);
  const [issue, setIssue] = useState<IssueApi | null>(null);
  const [projects, setProjects] = useState<ProjectApi[]>([]);
  const [deliverables, setDeliverables] = useState<Deliverable[]>([]);
  const [employees, setEmployees] = useState<Employee[]>([]);
  const [filteredDeliverables, setFilteredDeliverables] = useState<Deliverable[]>([]);
  const [selectedProjectId, setSelectedProjectId] = useState<number>(0);

  const form = useForm<IssueUpdateRequest>({
    defaultValues: {
      id: 0,
      biCode: "",
      type: "User Story",
      description: "",
      estimates: "",
      esUnit: 0,
      priority: "Medium",
      severity: "Medium",
      reportedBy: 0,
      assignedTo: 0,
      remainingHr: 0,
      title: "",
      projectId: 0,
      deliverablesId: 0
    }
  });

  // Step 1: Fetch the issue data first
  useEffect(() => {
    const fetchIssue = async () => {
      if (!id) {
        navigate("/issues");
        return;
      }
      
      const issueId = parseInt(id);
      if (isNaN(issueId)) {
        navigate("/issues");
        return;
      }
      
      try {
        setIsLoading(true);
        const issueData = await issuesApi.getById(issueId);
        setIssue(issueData);
        setSelectedProjectId(issueData.projectId);
        
        // Set form values
        form.reset({
          ...issueData
        });
      } catch (error) {
        console.error("Error fetching issue:", error);
        toast.error("Failed to load issue data. Please try again.");
        navigate("/issues");
      } finally {
        setIsLoading(false);
      }
    };
    
    fetchIssue();
  }, [id, navigate, form]);

  // Step 2: Fetch projects separately
  useEffect(() => {
    const fetchProjects = async () => {
      try {
        const projectsData = await projectService.getAll();
        setProjects(projectsData);
      } catch (error) {
        console.error("Error fetching projects:", error);
        toast.error("Failed to load projects. Some features may be limited.");
      }
    };
    
    fetchProjects();
  }, []);

  // Step 3: Fetch deliverables, but only after issue and projects are loaded
  useEffect(() => {
    if (!selectedProjectId) return;
    
    const fetchDeliverables = async () => {
      try {
        const deliverablesData = await deliverablesApi.getAll();
        setDeliverables(deliverablesData);
        
        // Filter deliverables based on the current project
        const filtered = deliverablesData.filter(d => d.projectId === selectedProjectId);
        setFilteredDeliverables(filtered);
      } catch (error) {
        console.error("Error fetching deliverables:", error);
        toast.error("Failed to load deliverables. Some features may be limited.");
      }
    };
    
    fetchDeliverables();
  }, [selectedProjectId]);

  // Step 4: Fetch employees separately
  useEffect(() => {
    const fetchEmployees = async () => {
      try {
        const employeesData = await employeeService.getAll();
        setEmployees(employeesData);
      } catch (error) {
        console.error("Error fetching employees:", error);
        toast.error("Failed to load employees. Some features may be limited.");
      }
    };
    
    fetchEmployees();
  }, []);

  // Handle project change to filter deliverables
  const handleProjectChange = (projectId: string) => {
    const numProjectId = parseInt(projectId);
    setSelectedProjectId(numProjectId);
    form.setValue("projectId", numProjectId);
    
    // Reset deliverable selection when project changes
    form.setValue("deliverablesId", 0);
  };

  const handleSubmit = async (data: IssueUpdateRequest) => {
    if (!validateForm(data)) {
      return;
    }
    
    setIsSubmitting(true);
    
    try {
      await issuesApi.update(data);
      toast.success("Issue updated successfully");
      navigate(`/issues/${data.id}`);
    } catch (error) {
      console.error("Error updating issue:", error);
      toast.error("Failed to update issue. Please try again.");
    } finally {
      setIsSubmitting(false);
    }
  };

  const validateForm = (data: IssueUpdateRequest): boolean => {
    if (!data.title.trim()) {
      toast.error("Title is required");
      return false;
    }
    
    if (!data.description.trim()) {
      toast.error("Description is required");
      return false;
    }
    
    if (data.projectId <= 0) {
      toast.error("Project is required");
      return false;
    }
    
    if (data.reportedBy <= 0) {
      toast.error("Reported By is required");
      return false;
    }
    
    if (data.assignedTo <= 0) {
      toast.error("Assigned To is required");
      return false;
    }
    
    if (data.deliverablesId <= 0) {
      toast.error("Deliverable is required");
      return false;
    }
    
    return true;
  };

  // Convert data to Dropdown options format
  const issueTypeOptions: DropdownOption[] = ["User Story", "Bug", "Task", "Documentation", "Enhancement"]
    .map(type => ({ label: type, value: type }));
  
  const priorityOptions: DropdownOption[] = ["Low", "Medium", "High", "Critical"]
    .map(priority => ({ label: priority, value: priority }));
  
  const severityOptions: DropdownOption[] = ["Low", "Medium", "High", "Critical"]
    .map(severity => ({ label: severity, value: severity }));

  const projectOptions: DropdownOption[] = projects.map(project => ({
    label: project.projectName,
    value: project.id.toString()
  }));
  
  const deliverableOptions: DropdownOption[] = filteredDeliverables.map(deliverable => ({
    label: deliverable.name,
    value: deliverable.id.toString()
  }));
  
  const employeeOptions: DropdownOption[] = employees.map(employee => ({
    label: `${employee.firstName} ${employee.lastName}`,
    value: employee.id.toString()
  }));
  
  const estimateUnitOptions: DropdownOption[] = [
    { label: "Hours", value: "Hours" },
    { label: "Days", value: "Days" }
  ];

  if (isLoading) {
    return (
      <Layout>
        <div className="flex justify-center items-center h-full">
          <Loader2 className="h-8 w-8 animate-spin text-primary" />
        </div>
      </Layout>
    );
  }

  return (
    <Layout>
      <div className="space-y-6 animate-fadeIn">
        <div className="flex items-center gap-4">
          <Button
            variant="ghost"
            size="icon"
            onClick={() => navigate(`/issues/${id}`)}
          >
            <ArrowLeft className="h-4 w-4" />
          </Button>
          <div>
            <h1 className="text-3xl font-bold tracking-tight">Edit Feature</h1>
            <p className="text-muted-foreground">
              Update issue #{id} details
            </p>
          </div>
        </div>

        <Form {...form}>
          <form onSubmit={form.handleSubmit(handleSubmit)}>
            <div className="grid grid-cols-1 gap-6">
              <Card>
                <CardHeader>
                  <CardTitle>Basic Information</CardTitle>
                  <CardDescription>
                    Edit the basic details of the Feature
                  </CardDescription>
                </CardHeader>
                <CardContent className="space-y-4">
                  <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                    <FormField
                      control={form.control}
                      name="title"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Title <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Input 
                              placeholder="Enter issue title" 
                              {...field} 
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                    
                    <FormField
                      control={form.control}
                      name="biCode"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>BI Code</FormLabel>
                          <FormControl>
                            <Input 
                              placeholder="Enter BI code (optional)" 
                              {...field} 
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                  </div>
                  
                  <FormField
                    control={form.control}
                    name="description"
                    render={({ field }) => (
                      <FormItem>
                        <FormLabel>Description <span className="text-destructive">*</span></FormLabel>
                        <FormControl>
                          <Textarea 
                            placeholder="Describe the issue in detail" 
                            rows={4}
                            {...field} 
                          />
                        </FormControl>
                        <FormMessage />
                      </FormItem>
                    )}
                  />
                </CardContent>
              </Card>

              <Card>
                <CardHeader>
                  <CardTitle>Classification</CardTitle>
                  <CardDescription>
                    Categorize and prioritize the issue
                  </CardDescription>
                </CardHeader>
                <CardContent className="space-y-4">
                  <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
                    <FormField
                      control={form.control}
                      name="type"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Type <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Dropdown
                              options={issueTypeOptions}
                              value={field.value}
                              onValueChange={field.onChange}
                              placeholder="Select type"
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                    
                    <FormField
                      control={form.control}
                      name="priority"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Priority <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Dropdown
                              options={priorityOptions}
                              value={field.value}
                              onValueChange={field.onChange}
                              placeholder="Select priority"
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                    
                    <FormField
                      control={form.control}
                      name="severity"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Severity <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Dropdown
                              options={severityOptions}
                              value={field.value}
                              onValueChange={field.onChange}
                              placeholder="Select severity"
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                  </div>
                </CardContent>
              </Card>

              <Card>
                <CardHeader>
                  <CardTitle>Project & Assignment</CardTitle>
                  <CardDescription>
                    Link the issue to a project and assign it to a team member
                  </CardDescription>
                </CardHeader>
                <CardContent className="space-y-4">
                  <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                    <FormField
                      control={form.control}
                      name="projectId"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Project <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Dropdown
                              options={projectOptions}
                              value={field.value > 0 ? field.value.toString() : ""}
                              onValueChange={handleProjectChange}
                              placeholder="Select project"
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                    
                    <FormField
                      control={form.control}
                      name="deliverablesId"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Deliverable <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Dropdown
                              options={deliverableOptions}
                              value={field.value > 0 ? field.value.toString() : ""}
                              onValueChange={(value) => form.setValue("deliverablesId", parseInt(value))}
                              placeholder={
                                selectedProjectId <= 0 
                                  ? "Select a project first" 
                                  : filteredDeliverables.length === 0 
                                    ? "No deliverables found" 
                                    : "Select deliverable"
                              }
                              disabled={selectedProjectId <= 0 || filteredDeliverables.length === 0}
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                  </div>
                  
                  <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                    <FormField
                      control={form.control}
                      name="reportedBy"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Reported By <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Dropdown
                              options={employeeOptions}
                              value={field.value > 0 ? field.value.toString() : ""}
                              onValueChange={(value) => form.setValue("reportedBy", parseInt(value))}
                              placeholder="Select reporter"
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                    
                    <FormField
                      control={form.control}
                      name="assignedTo"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Assigned To <span className="text-destructive">*</span></FormLabel>
                          <FormControl>
                            <Dropdown
                              options={employeeOptions}
                              value={field.value > 0 ? field.value.toString() : ""}
                              onValueChange={(value) => form.setValue("assignedTo", parseInt(value))}
                              placeholder="Select assignee"
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                  </div>
                </CardContent>
              </Card>

              <Card>
                <CardHeader>
                  <CardTitle>Effort Estimation</CardTitle>
                  <CardDescription>
                    Estimate the work effort required
                  </CardDescription>
                </CardHeader>
                <CardContent className="space-y-4">
                  <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
                    <FormField
                      control={form.control}
                      name="estimates"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Estimates Description</FormLabel>
                          <FormControl>
                            <Input 
                              placeholder="e.g., 2 days, 4 hours" 
                              {...field} 
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                    
                    <FormField
                      control={form.control}
                      name="esUnit"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Estimate Units</FormLabel>
                          <FormControl>
                            <select
                              className="flex h-10 w-full rounded-md border border-input bg-background px-3 py-2 text-sm ring-offset-background file:border-0 file:bg-transparent file:text-sm file:font-medium placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50"
                              value={field.value >= 8 ? "Days" : "Hours"}
                              onChange={(e) => {
                                const value = e.target.value;
                                const numValue = value === "Hours" ? 1 : 8;
                                form.setValue("esUnit", numValue);
                              }}
                            >
                              <option value="Hours">Hours</option>
                              <option value="Days">Days</option>
                            </select>
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                    
                    <FormField
                      control={form.control}
                      name="remainingHr"
                      render={({ field }) => (
                        <FormItem>
                          <FormLabel>Remaining Hours</FormLabel>
                          <FormControl>
                            <Input 
                              type="number"
                              placeholder="Enter hours" 
                              {...field}
                              onChange={(e) => form.setValue("remainingHr", parseInt(e.target.value) || 0)}
                            />
                          </FormControl>
                          <FormMessage />
                        </FormItem>
                      )}
                    />
                  </div>
                </CardContent>
              </Card>

              <div className="flex justify-end gap-4">
                <Button
                  type="button"
                  variant="outline"
                  onClick={() => navigate(`/issues/${id}`)}
                >
                  Cancel
                </Button>
              
                <Button type="submit" disabled={isSubmitting}>
                  {isSubmitting ? (
                    <>
                      <Loader2 className="mr-2 h-4 w-4 animate-spin" />
                      Updating...
                    </>
                  ) : (
                    "Update Feature"
                  )}
                </Button>
              </div>
            </div>
          </form>
        </Form>
      </div>
    </Layout>
  );
};

export default IssueEdit;