import { dbGlobal } from "drizzle-pkg/lib/db";
import { agents, agentToolAssociations } from "drizzle-pkg/lib/schema/agent";
import { agentTools } from "drizzle-pkg/lib/schema/agent-tool";
import { eq, and, asc, sql } from "drizzle-orm";
import type { AgentToolRow } from "#server/service/agent-tool";

export type AgentRow = typeof agents.$inferSelect;

export type AgentTitleStrategy = "llm" | "first-line" | "none";

export interface AgentWithTools extends AgentRow {
  tools: AgentToolRow[];
}

export interface CreateAgentInput {
  slug: string;
  name: string;
  description?: string;
  systemPrompt: string;
  defaultModelId?: number | null;
  titleModelId?: number | null;
  titleStrategy?: AgentTitleStrategy;
  enableThinking?: number;
  enableTools?: number;
  maxStepCount?: number;
  isDefault?: number;
  isCallable?: number;
  sortOrder?: number;
  enabled?: number;
  toolIds?: string[];
}

export interface UpdateAgentInput {
  slug?: string;
  name?: string;
  description?: string;
  systemPrompt?: string;
  defaultModelId?: number | null;
  titleModelId?: number | null;
  titleStrategy?: AgentTitleStrategy;
  enableThinking?: number;
  enableTools?: number;
  maxStepCount?: number;
  isDefault?: number;
  isCallable?: number;
  sortOrder?: number;
  enabled?: number;
  toolIds?: string[];
}

export async function getAgentBySlug(slug: string): Promise<AgentRow | null> {
  const [row] = await dbGlobal
    .select()
    .from(agents)
    .where(and(eq(agents.slug, slug), eq(agents.enabled, 1)))
    .limit(1);
  return row ?? null;
}

export async function getAgentBySlugAny(slug: string): Promise<AgentRow | null> {
  const [row] = await dbGlobal
    .select()
    .from(agents)
    .where(eq(agents.slug, slug))
    .limit(1);
  return row ?? null;
}

export async function getAgentById(id: number): Promise<AgentRow | null> {
  const [row] = await dbGlobal.select().from(agents).where(eq(agents.id, id)).limit(1);
  return row ?? null;
}

export async function getDefaultAgent(): Promise<AgentRow | null> {
  const [row] = await dbGlobal
    .select()
    .from(agents)
    .where(and(eq(agents.isDefault, 1), eq(agents.enabled, 1)))
    .limit(1);
  if (row) return row;
  const [fallback] = await dbGlobal
    .select()
    .from(agents)
    .where(eq(agents.enabled, 1))
    .orderBy(asc(agents.sortOrder))
    .limit(1);
  return fallback ?? null;
}

export async function listAgents(onlyEnabled = true): Promise<AgentRow[]> {
  const where = onlyEnabled ? eq(agents.enabled, 1) : sql`1=1`;
  return dbGlobal.select().from(agents).where(where).orderBy(asc(agents.sortOrder), asc(agents.id));
}

export async function getAgentWithTools(slug: string): Promise<AgentWithTools | null> {
  const agent = await getAgentBySlug(slug);
  if (!agent) return null;
  const tools = await getAgentTools(agent.id);
  return { ...agent, tools };
}

export async function getAgentTools(agentId: number): Promise<AgentToolRow[]> {
  const rows = await dbGlobal
    .select({
      tool: agentTools,
      sortOrder: agentToolAssociations.sortOrder,
    })
    .from(agentToolAssociations)
    .innerJoin(agentTools, eq(agentToolAssociations.toolId, agentTools.id))
    .where(and(eq(agentToolAssociations.agentId, agentId), eq(agentTools.enabled, 1)))
    .orderBy(asc(agentToolAssociations.sortOrder), asc(agentTools.sortOrder));
  return rows.map((r) => r.tool);
}

export async function getAgentToolIds(agentId: number): Promise<string[]> {
  const tools = await getAgentTools(agentId);
  return tools.map((t) => t.id);
}

export async function createAgent(input: CreateAgentInput): Promise<AgentRow> {
  const existing = await getAgentBySlugAny(input.slug);
  if (existing) {
    throw new Error(`slug 已存在: ${input.slug}`);
  }
  const [row] = await dbGlobal
    .insert(agents)
    .values({
      slug: input.slug,
      name: input.name,
      description: input.description ?? null,
      systemPrompt: input.systemPrompt,
      defaultModelId: input.defaultModelId ?? null,
      titleModelId: input.titleModelId ?? null,
      titleStrategy: input.titleStrategy ?? "llm",
      enableThinking: input.enableThinking ?? 0,
      enableTools: input.enableTools ?? 1,
      maxStepCount: input.maxStepCount ?? 6,
      isDefault: input.isDefault ?? 0,
      isCallable: input.isCallable ?? 0,
      sortOrder: input.sortOrder ?? 0,
      enabled: input.enabled ?? 1,
    })
    .returning();
  if (!row) throw new Error("创建 agent 失败");

  if (input.isDefault === 1) {
    await dbGlobal
      .update(agents)
      .set({ isDefault: 0 })
      .where(and(sql`${agents.id} != ${row.id}`));
  }

  if (input.toolIds && input.toolIds.length > 0) {
    for (let i = 0; i < input.toolIds.length; i++) {
      const toolId = input.toolIds[i]!;
      await dbGlobal.insert(agentToolAssociations).values({
        agentId: row.id,
        toolId,
        sortOrder: i,
      });
    }
  }
  return row;
}

export async function updateAgent(id: number, input: UpdateAgentInput): Promise<AgentRow | null> {
  const existing = await getAgentById(id);
  if (!existing) return null;

  if (input.slug && input.slug !== existing.slug) {
    const slugConflict = await getAgentBySlugAny(input.slug);
    if (slugConflict) {
      throw new Error(`slug 已存在: ${input.slug}`);
    }
  }

  const updates: Partial<AgentRow> = {};
  if (input.slug !== undefined) updates.slug = input.slug;
  if (input.name !== undefined) updates.name = input.name;
  if (input.description !== undefined) updates.description = input.description;
  if (input.systemPrompt !== undefined) updates.systemPrompt = input.systemPrompt;
  if (input.defaultModelId !== undefined) updates.defaultModelId = input.defaultModelId;
  if (input.titleModelId !== undefined) updates.titleModelId = input.titleModelId;
  if (input.titleStrategy !== undefined) updates.titleStrategy = input.titleStrategy;
  if (input.enableThinking !== undefined) updates.enableThinking = input.enableThinking;
  if (input.enableTools !== undefined) updates.enableTools = input.enableTools;
  if (input.maxStepCount !== undefined) updates.maxStepCount = input.maxStepCount;
  if (input.isCallable !== undefined) updates.isCallable = input.isCallable;
  if (input.sortOrder !== undefined) updates.sortOrder = input.sortOrder;
  if (input.enabled !== undefined) updates.enabled = input.enabled;

  if (input.isDefault !== undefined) {
    updates.isDefault = input.isDefault;
    if (input.isDefault === 1) {
      await dbGlobal
        .update(agents)
        .set({ isDefault: 0 })
        .where(and(sql`${agents.id} != ${id}`));
    }
  }

  if (Object.keys(updates).length > 0) {
    await dbGlobal.update(agents).set(updates).where(eq(agents.id, id));
  }

  if (input.toolIds !== undefined) {
    await dbGlobal.delete(agentToolAssociations).where(eq(agentToolAssociations.agentId, id));
    for (let i = 0; i < input.toolIds.length; i++) {
      const toolId = input.toolIds[i]!;
      await dbGlobal.insert(agentToolAssociations).values({
        agentId: id,
        toolId,
        sortOrder: i,
      });
    }
  }

  return getAgentById(id);
}

export async function deleteAgent(id: number): Promise<void> {
  await dbGlobal.delete(agentToolAssociations).where(eq(agentToolAssociations.agentId, id));
  await dbGlobal.delete(agents).where(eq(agents.id, id));
}