"use client";

import { useState } from "react";
import { Button } from "@/components/ui/button";
import type { ScenarioInputPayload } from "@/lib/api";

const LOCATION_OPTIONS = [
  { value: "RJ", label: "Rajasthan (High Solar)" },
  { value: "GJ", label: "Gujarat (High Solar)" },
  { value: "AP", label: "Andhra Pradesh" },
  { value: "TN", label: "Tamil Nadu" },
  { value: "MP", label: "Madhya Pradesh" },
  { value: "KA", label: "Karnataka" },
];

const STEP_LABELS = [
  "Project Info",
  "Solar",
  "Wind",
  "BESS",
  "Solver",
  "Review",
];

interface WizardState {
  name: string;
  cod_date: string;
  // Solar
  solar_enabled: boolean;
  solar_location: string;
  solar_ac_mw: number;
  solar_dc_ac_ratio: number;
  solar_dc_mwp: number;
  // Wind
  wind_enabled: boolean;
  wind_location: string;
  wind_mw: number;
  // BESS
  bess_enabled: boolean;
  bess_mwh: number;
  bess_mw: number;
  // Solver
  solver_mode: "solve_tariff" | "fixed_tariff";
  target_irr: number;
  fixed_tariff: number;
}

const DEFAULT_STATE: WizardState = {
  name: "",
  cod_date: "2027-04-01",
  solar_enabled: true,
  solar_location: "RJ",
  solar_ac_mw: 100,
  solar_dc_ac_ratio: 1.4,
  solar_dc_mwp: 140,
  wind_enabled: false,
  wind_location: "RJ",
  wind_mw: 50,
  bess_enabled: false,
  bess_mwh: 200,
  bess_mw: 50,
  solver_mode: "solve_tariff",
  target_irr: 0.18,
  fixed_tariff: 3.5,
};

function Field({
  label,
  children,
}: {
  label: string;
  children: React.ReactNode;
}) {
  return (
    <div className="flex flex-col gap-1">
      <label className="text-sm font-medium text-foreground">{label}</label>
      {children}
    </div>
  );
}

function Input({
  value,
  onChange,
  type = "text",
  step,
  min,
  max,
  readOnly,
  className = "",
}: {
  value: string | number;
  onChange: (v: string) => void;
  type?: string;
  step?: number;
  min?: number;
  max?: number;
  readOnly?: boolean;
  className?: string;
}) {
  return (
    <input
      type={type}
      step={step}
      min={min}
      max={max}
      readOnly={readOnly}
      value={value}
      onChange={(e) => onChange(e.target.value)}
      className={`border rounded px-3 py-1.5 text-sm focus:outline-none focus:ring-2 focus:ring-primary bg-background ${readOnly ? "bg-muted cursor-default" : ""} ${className}`}
    />
  );
}

function Select({
  value,
  onChange,
  options,
}: {
  value: string;
  onChange: (v: string) => void;
  options: { value: string; label: string }[];
}) {
  return (
    <select
      value={value}
      onChange={(e) => onChange(e.target.value)}
      className="border rounded px-3 py-1.5 text-sm focus:outline-none focus:ring-2 focus:ring-primary bg-background"
    >
      {options.map((o) => (
        <option key={o.value} value={o.value}>
          {o.label}
        </option>
      ))}
    </select>
  );
}

function Toggle({
  label,
  checked,
  onChange,
}: {
  label: string;
  checked: boolean;
  onChange: (v: boolean) => void;
}) {
  return (
    <label className="flex items-center gap-2 cursor-pointer">
      <input
        type="checkbox"
        checked={checked}
        onChange={(e) => onChange(e.target.checked)}
        className="w-4 h-4 accent-primary"
      />
      <span className="text-sm font-medium">{label}</span>
    </label>
  );
}

// ---------------------------------------------------------------------------
// Step components
// ---------------------------------------------------------------------------

function StepProjectInfo({
  state,
  set,
}: {
  state: WizardState;
  set: (k: keyof WizardState, v: WizardState[keyof WizardState]) => void;
}) {
  return (
    <div className="flex flex-col gap-4">
      <h2 className="text-lg font-semibold">Project Information</h2>
      <Field label="Scenario name *">
        <Input
          value={state.name}
          onChange={(v) => set("name", v)}
        />
      </Field>
      <Field label="Commercial Operation Date (COD)">
        <Input
          type="date"
          value={state.cod_date}
          onChange={(v) => set("cod_date", v)}
        />
      </Field>
    </div>
  );
}

function StepSolar({
  state,
  set,
}: {
  state: WizardState;
  set: (k: keyof WizardState, v: WizardState[keyof WizardState]) => void;
}) {
  return (
    <div className="flex flex-col gap-4">
      <h2 className="text-lg font-semibold">Solar Generation</h2>
      <Toggle
        label="Include Solar"
        checked={state.solar_enabled}
        onChange={(v) => set("solar_enabled", v)}
      />
      {state.solar_enabled && (
        <>
          <Field label="Location">
            <Select
              value={state.solar_location}
              onChange={(v) => set("solar_location", v)}
              options={LOCATION_OPTIONS}
            />
          </Field>
          <Field label="AC Capacity (MW)">
            <Input
              type="number"
              value={state.solar_ac_mw}
              step={5}
              min={1}
              onChange={(v) => set("solar_ac_mw", Number(v))}
            />
          </Field>
          <Field label="DC:AC Ratio">
            <Input
              type="number"
              value={state.solar_dc_ac_ratio}
              step={0.05}
              min={1.0}
              max={1.8}
              onChange={(v) => {
                const ratio = Number(v);
                set("solar_dc_ac_ratio", ratio);
                set("solar_dc_mwp", parseFloat((state.solar_ac_mw * ratio).toFixed(3)));
              }}
            />
          </Field>
          <Field label="DC Capacity (MWp)">
            <Input
              type="number"
              value={state.solar_dc_mwp}
              step={5}
              min={1}
              readOnly
              className="bg-muted cursor-default"
              onChange={() => {}}
            />
          </Field>
        </>
      )}
    </div>
  );
}

function StepWind({
  state,
  set,
}: {
  state: WizardState;
  set: (k: keyof WizardState, v: WizardState[keyof WizardState]) => void;
}) {
  return (
    <div className="flex flex-col gap-4">
      <h2 className="text-lg font-semibold">Wind Generation</h2>
      <Toggle
        label="Include Wind"
        checked={state.wind_enabled}
        onChange={(v) => set("wind_enabled", v)}
      />
      {state.wind_enabled && (
        <>
          <Field label="Location">
            <Select
              value={state.wind_location}
              onChange={(v) => set("wind_location", v)}
              options={LOCATION_OPTIONS}
            />
          </Field>
          <Field label="Capacity (MW)">
            <Input
              type="number"
              value={state.wind_mw}
              step={5}
              min={1}
              onChange={(v) => set("wind_mw", Number(v))}
            />
          </Field>
        </>
      )}
    </div>
  );
}

function StepBess({
  state,
  set,
}: {
  state: WizardState;
  set: (k: keyof WizardState, v: WizardState[keyof WizardState]) => void;
}) {
  return (
    <div className="flex flex-col gap-4">
      <h2 className="text-lg font-semibold">BESS (Battery Storage)</h2>
      <Toggle
        label="Include BESS"
        checked={state.bess_enabled}
        onChange={(v) => set("bess_enabled", v)}
      />
      {state.bess_enabled && (
        <>
          <Field label="Energy Capacity (MWh)">
            <Input
              type="number"
              value={state.bess_mwh}
              step={10}
              min={10}
              onChange={(v) => set("bess_mwh", Number(v))}
            />
          </Field>
          <Field label="Power Capacity (MW)">
            <Input
              type="number"
              value={state.bess_mw}
              step={5}
              min={5}
              onChange={(v) => set("bess_mw", Number(v))}
            />
          </Field>
        </>
      )}
    </div>
  );
}

function StepSolver({
  state,
  set,
}: {
  state: WizardState;
  set: (k: keyof WizardState, v: WizardState[keyof WizardState]) => void;
}) {
  return (
    <div className="flex flex-col gap-4">
      <h2 className="text-lg font-semibold">Solver & Tariff</h2>
      <Field label="Mode">
        <Select
          value={state.solver_mode}
          onChange={(v) => set("solver_mode", v as "solve_tariff" | "fixed_tariff")}
          options={[
            { value: "solve_tariff", label: "Solve tariff for target IRR" },
            { value: "fixed_tariff", label: "Fixed tariff" },
          ]}
        />
      </Field>
      {state.solver_mode === "solve_tariff" ? (
        <Field label="Target Equity IRR (e.g. 0.18 = 18%)">
          <Input
            type="number"
            value={state.target_irr}
            step={0.01}
            min={0.05}
            onChange={(v) => set("target_irr", Number(v))}
          />
        </Field>
      ) : (
        <Field label="Fixed Tariff (INR/kWh)">
          <Input
            type="number"
            value={state.fixed_tariff}
            step={0.1}
            min={1}
            onChange={(v) => set("fixed_tariff", Number(v))}
          />
        </Field>
      )}
    </div>
  );
}

function StepReview({ state }: { state: WizardState }) {
  return (
    <div className="flex flex-col gap-4">
      <h2 className="text-lg font-semibold">Review & Submit</h2>
      <dl className="grid grid-cols-2 gap-2 text-sm">
        <dt className="text-muted-foreground">Name</dt>
        <dd>{state.name || "—"}</dd>
        <dt className="text-muted-foreground">COD</dt>
        <dd>{state.cod_date}</dd>
        {state.solar_enabled && (
          <>
            <dt className="text-muted-foreground">Solar</dt>
            <dd>
              {state.solar_ac_mw} MW AC / {state.solar_dc_mwp} MWp DC ({state.solar_location}, {state.solar_dc_ac_ratio}x)
            </dd>
          </>
        )}
        {state.wind_enabled && (
          <>
            <dt className="text-muted-foreground">Wind</dt>
            <dd>
              {state.wind_mw} MW ({state.wind_location})
            </dd>
          </>
        )}
        {state.bess_enabled && (
          <>
            <dt className="text-muted-foreground">BESS</dt>
            <dd>
              {state.bess_mwh} MWh / {state.bess_mw} MW
            </dd>
          </>
        )}
        <dt className="text-muted-foreground">Solver</dt>
        <dd>
          {state.solver_mode === "solve_tariff"
            ? `Solve tariff @ IRR ${(state.target_irr * 100).toFixed(0)}%`
            : `Fixed ₹${state.fixed_tariff}/kWh`}
        </dd>
      </dl>
    </div>
  );
}

// ---------------------------------------------------------------------------
// Main wizard
// ---------------------------------------------------------------------------

interface ScenarioWizardProps {
  onSubmit: (name: string, inputs: ScenarioInputPayload) => Promise<void>;
  onCancel: () => void;
}

export function ScenarioWizard({ onSubmit, onCancel }: ScenarioWizardProps) {
  const [step, setStep] = useState(0);
  const [state, setState] = useState<WizardState>(DEFAULT_STATE);
  const [submitting, setSubmitting] = useState(false);
  const [error, setError] = useState<string | null>(null);

  function set<K extends keyof WizardState>(k: K, v: WizardState[K]) {
    setState((prev) => ({ ...prev, [k]: v }));
  }

  const steps = [
    <StepProjectInfo key="0" state={state} set={set} />,
    <StepSolar key="1" state={state} set={set} />,
    <StepWind key="2" state={state} set={set} />,
    <StepBess key="3" state={state} set={set} />,
    <StepSolver key="4" state={state} set={set} />,
    <StepReview key="5" state={state} />,
  ];

  function buildInputs(): ScenarioInputPayload {
    return {
      project: {
        name: state.name,
        capacity_solar_mwp: state.solar_enabled ? state.solar_dc_mwp : 0,
        capacity_wind_mw: state.wind_enabled ? state.wind_mw : 0,
        capacity_bess_mwh: state.bess_enabled ? state.bess_mwh : 0,
        capacity_bess_mw: state.bess_enabled ? state.bess_mw : 0,
        cod_date: state.cod_date,
      },
      solar: state.solar_enabled
        ? {
            location_id: state.solar_location,
            capacity_ac_mw: state.solar_ac_mw,
            dc_ac_ratio: state.solar_dc_ac_ratio,
            capacity_dc_mwp: state.solar_dc_mwp,
          }
        : null,
      wind: state.wind_enabled
        ? { location_id: state.wind_location, capacity_mw: state.wind_mw }
        : null,
      solver:
        state.solver_mode === "fixed_tariff"
          ? {
              mode: "fixed_tariff",
              fixed_tariff: state.fixed_tariff,
            }
          : {
              mode: "solve_tariff",
              target_equity_irr: state.target_irr,
            },
    };
  }

  async function handleSubmit() {
    if (!state.name.trim()) {
      setError("Please enter a scenario name.");
      return;
    }
    setSubmitting(true);
    setError(null);
    try {
      await onSubmit(state.name, buildInputs());
    } catch (e) {
      setError(e instanceof Error ? e.message : "Unknown error");
      setSubmitting(false);
    }
  }

  const isLast = step === steps.length - 1;

  return (
    <div className="flex flex-col gap-6">
      {/* Progress bar */}
      <div className="flex gap-1">
        {STEP_LABELS.map((label, i) => (
          <div key={label} className="flex-1 flex flex-col items-center gap-1">
            <div
              className={`h-1.5 w-full rounded-full ${i <= step ? "bg-primary" : "bg-muted"}`}
            />
            <span
              className={`text-xs ${i === step ? "text-primary font-medium" : "text-muted-foreground"}`}
            >
              {label}
            </span>
          </div>
        ))}
      </div>

      {/* Step content */}
      <div className="min-h-[280px]">{steps[step]}</div>

      {error && (
        <p className="text-sm text-red-600 bg-red-50 px-3 py-2 rounded">
          {error}
        </p>
      )}

      {/* Navigation */}
      <div className="flex justify-between">
        <div className="flex gap-2">
          <Button variant="ghost" onClick={onCancel} disabled={submitting}>
            Cancel
          </Button>
          {step > 0 && (
            <Button
              variant="outline"
              onClick={() => setStep((s) => s - 1)}
              disabled={submitting}
            >
              Back
            </Button>
          )}
        </div>
        {isLast ? (
          <Button onClick={handleSubmit} disabled={submitting}>
            {submitting ? "Submitting…" : "Run Scenario"}
          </Button>
        ) : (
          <Button onClick={() => setStep((s) => s + 1)}>Next</Button>
        )}
      </div>
    </div>
  );
}