/**
 * Spec-to-PR (experimental).
 *
 * Pipeline:
 *   1. Validate prerequisites: API key present, repo exists, user can be
 *      resolved for author metadata.
 *   2. `buildSpecContext` — read the bare repo, score paths against the spec,
 *      collect a bounded file list + top-N relevant file contents.
 *   3. `generateSpecEdits` — send that context to Claude; parse + validate the
 *      proposed edits (forbidden paths filtered defence-in-depth).
 *   4. `applyEditsToNewBranch` — write the edits to a fresh branch via git
 *      plumbing (bare repo, no working tree).
 *   5. Insert a draft `pullRequests` row pointing base→head.
 *
 * Every failure mode is funnelled through `{ok:false, error}`. We never throw
 * — the route (`src/routes/specs.tsx`) renders the error inline.
 */
import { join } from "path";
import { eq } from "drizzle-orm";
import { db } from "../db";
import { repositories, users, pullRequests } from "../db/schema";
import { buildSpecContext } from "./spec-context";
import { generateSpecEdits } from "./spec-ai";
import { applyEditsToNewBranch } from "./spec-git";

export type SpecPRArgs = {
  repoId: string;
  spec: string;
  baseRef?: string;
  userId: string;
};

export type SpecPRResult =
  | {
      ok: true;
      prNumber: number;
      branchName: string;
      filesChanged: string[];
    }
  | { ok: false; error: string };

/** Derive a filesystem-safe branch suffix from the user's spec. */
function slugify(spec: string): string {
  const base = spec
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "")
    .slice(0, 40);
  return base || "change";
}

function randomSuffix(): string {
  return Math.random().toString(16).slice(2, 8);
}

export async function createSpecPR(args: SpecPRArgs): Promise<SpecPRResult> {
  // 1. API key gate. Without it the AI step would fail anyway — bail before
  //    any DB or disk work.
  if (!process.env.ANTHROPIC_API_KEY) {
    return { ok: false, error: "ANTHROPIC_API_KEY required for spec-to-PR" };
  }

  const spec = typeof args.spec === "string" ? args.spec.trim() : "";
  if (!spec) return { ok: false, error: "spec is empty" };

  // 2. Resolve repo + owner so we can build the on-disk path.
  let repoRow: {
    id: string;
    name: string;
    defaultBranch: string | null;
    ownerName: string | null;
  } | undefined;
  try {
    const rows = await db
      .select({
        id: repositories.id,
        name: repositories.name,
        defaultBranch: repositories.defaultBranch,
        ownerName: users.username,
      })
      .from(repositories)
      .leftJoin(users, eq(users.id, repositories.ownerId))
      .where(eq(repositories.id, args.repoId))
      .limit(1);
    repoRow = rows[0];
  } catch {
    return { ok: false, error: "db lookup failed" };
  }
  if (!repoRow || !repoRow.ownerName) {
    return { ok: false, error: "repo not found" };
  }

  // 3. Resolve the author — needed for the commit-tree call and the PR row.
  let authorRow: { username: string; email: string | null } | undefined;
  try {
    const rows = await db
      .select({ username: users.username, email: users.email })
      .from(users)
      .where(eq(users.id, args.userId))
      .limit(1);
    authorRow = rows[0];
  } catch {
    return { ok: false, error: "db lookup failed" };
  }
  if (!authorRow) return { ok: false, error: "author not found" };

  const base = process.env.GIT_REPOS_PATH || "./repos";
  const repoDiskPath = join(base, repoRow.ownerName, `${repoRow.name}.git`);
  const defaultBranch = repoRow.defaultBranch || "main";
  const baseRef = (args.baseRef && args.baseRef.trim()) || defaultBranch;

  // 4. Build context.
  const ctx = await buildSpecContext({
    repoDiskPath,
    spec,
    defaultBranch: baseRef,
  });
  if (!ctx.ok) {
    return { ok: false, error: `context build failed: ${ctx.error}` };
  }

  // 5. Ask Claude for edits.
  const ai = await generateSpecEdits({
    spec,
    fileList: ctx.context.fileList,
    relevantFiles: ctx.context.relevantFiles,
    defaultBranch: ctx.context.defaultBranch,
  });
  if (!ai.ok) return { ok: false, error: `AI failed: ${ai.error}` };
  if (ai.edits.length === 0) {
    return { ok: false, error: "AI proposed no changes" };
  }

  // 6. Apply edits to a fresh branch via git plumbing.
  const branchName = `spec/${slugify(spec)}-${randomSuffix()}`;
  const commitSubject = ai.summary || `spec: ${spec.slice(0, 60)}`;
  const commitBody = `Generated by spec-to-PR.\n\nSpec:\n${spec}`;
  const commitMessage = `${commitSubject}\n\n${commitBody}`;

  const authorEmail =
    authorRow.email || `${authorRow.username}@users.noreply.gluecron`;
  const applied = await applyEditsToNewBranch({
    repoDiskPath,
    baseRef,
    edits: ai.edits,
    branchName,
    commitMessage,
    authorName: authorRow.username,
    authorEmail,
  });
  if (!applied.ok) return { ok: false, error: `git apply failed: ${applied.error}` };

  // 7. Insert the draft PR row.
  try {
    const [pr] = await db
      .insert(pullRequests)
      .values({
        repositoryId: repoRow.id,
        authorId: args.userId,
        title: commitSubject.slice(0, 200),
        body: `${commitBody}\n\nFiles changed:\n${applied.filesChanged
          .map((p) => `- ${p}`)
          .join("\n")}`,
        baseBranch: baseRef,
        headBranch: applied.branchName,
        isDraft: true,
      })
      .returning();
    const number = pr?.number;
    if (typeof number !== "number") {
      return { ok: false, error: "PR insert returned no number" };
    }
    return {
      ok: true,
      prNumber: number,
      branchName: applied.branchName,
      filesChanged: applied.filesChanged,
    };
  } catch (err) {
    return {
      ok: false,
      error: `PR insert failed: ${err instanceof Error ? err.message : String(err)}`,
    };
  }
}