import type { IModelCatalogEntry } from '../interfaces/catalog.ts';
import type { IGpuInfo, TGpuVendor } from '../interfaces/gpu.ts';
import type { IClusterGpuTopologyGroup } from '../interfaces/cluster.ts';

function parsePciBusNumber(gpu: IGpuInfo): number {
  const source = gpu.pciBusId || gpu.pciSlot;
  const match = source.match(/(?:[0-9a-f]{4}:)?([0-9a-f]{2}):/i);
  if (!match) {
    return gpu.index;
  }

  return parseInt(match[1], 16);
}

export function buildGpuTopologyGroups(gpus: IGpuInfo[]): IClusterGpuTopologyGroup[] {
  const sorted = [...gpus].sort((left, right) => {
    if (left.vendor !== right.vendor) {
      return left.vendor.localeCompare(right.vendor);
    }

    return parsePciBusNumber(left) - parsePciBusNumber(right);
  });

  const groups: IClusterGpuTopologyGroup[] = [];

  for (const gpu of sorted) {
    const busNumber = parsePciBusNumber(gpu);
    const previousGroup = groups[groups.length - 1];
    const previousBus = previousGroup?.busNumbers[previousGroup.busNumbers.length - 1];

    const belongsToPreviousGroup = previousGroup &&
      previousGroup.vendor === gpu.vendor &&
      previousBus !== undefined &&
      busNumber - previousBus <= 1;

    if (belongsToPreviousGroup) {
      previousGroup.gpuIds.push(gpu.id);
      previousGroup.busNumbers.push(busNumber);
      previousGroup.totalVramGb += Math.round(gpu.vram / 1024);
      previousGroup.maxSingleGpuVramGb = Math.max(
        previousGroup.maxSingleGpuVramGb,
        Math.round(gpu.vram / 1024),
      );
      continue;
    }

    groups.push({
      id: `${gpu.vendor}-${groups.length + 1}`,
      vendor: gpu.vendor,
      gpuIds: [gpu.id],
      gpuCount: 1,
      totalVramGb: Math.round(gpu.vram / 1024),
      maxSingleGpuVramGb: Math.round(gpu.vram / 1024),
      busNumbers: [busNumber],
    });
  }

  for (const group of groups) {
    group.gpuCount = group.gpuIds.length;
  }

  return groups;
}

export function summarizeGpuTopologyGroups(gpus: IGpuInfo[]): IClusterGpuTopologyGroup[] {
  return buildGpuTopologyGroups(gpus);
}

export function selectPlacementForModel(
  model: IModelCatalogEntry,
  gpus: IGpuInfo[],
): { gpuIds: string[]; tensorParallelSize: number; topologyGroupId: string } | null {
  const minGpuCount = model.requirements.minGpuCount || 1;
  const preferredTensorParallel = model.launchDefaults?.tensorParallelSize || minGpuCount;
  const topologyGroups = buildGpuTopologyGroups(gpus);

  const eligibleGroups = topologyGroups.filter((group) =>
    group.gpuCount >= minGpuCount && group.totalVramGb >= model.requirements.minVramGb
  );

  if (eligibleGroups.length === 0) {
    return null;
  }

  eligibleGroups.sort((left, right) => {
    const leftCountDelta = Math.abs(left.gpuCount - preferredTensorParallel);
    const rightCountDelta = Math.abs(right.gpuCount - preferredTensorParallel);
    if (leftCountDelta !== rightCountDelta) {
      return leftCountDelta - rightCountDelta;
    }

    const leftVramDelta = left.totalVramGb - model.requirements.minVramGb;
    const rightVramDelta = right.totalVramGb - model.requirements.minVramGb;
    if (leftVramDelta !== rightVramDelta) {
      return leftVramDelta - rightVramDelta;
    }

    return left.id.localeCompare(right.id);
  });

  const selectedGroup = eligibleGroups[0];
  const tensorParallelSize = Math.min(preferredTensorParallel, selectedGroup.gpuCount);

  return {
    gpuIds: selectedGroup.gpuIds.slice(0, tensorParallelSize),
    tensorParallelSize,
    topologyGroupId: selectedGroup.id,
  };
}

export function filterOutUsedGpus(gpus: IGpuInfo[], usedGpuIds: string[]): IGpuInfo[] {
  const usedSet = new Set(usedGpuIds);
  return gpus.filter((gpu) => !usedSet.has(gpu.id));
}