import { execa } from "execa";
import { z } from "zod";
import { truncate } from "../utils/truncate.js";
import type { ToolDef } from "./types.js";

async function tryGit(args: string[], cwd: string): Promise<string> {
  try {
    const result = await execa("git", args, { cwd, reject: false });
    return result.exitCode === 0 ? result.stdout : "";
  } catch {
    return "";
  }
}

function runGit(args: string[], cwd: string) {
  return execa("git", args, { cwd, reject: false });
}

// --- git_status: read-only inspection, auto-runs like grep/read_file ---

const statusSchema = z.object({
  operation: z.enum(["status", "diff", "log", "show", "branches"]),
  paths: z.array(z.string()).optional().describe("Limit `status`/`diff` to these paths, relative to the working directory."),
  staged: z.boolean().optional().describe("For `diff`: show staged changes (--cached) instead of the working tree diff."),
  ref: z.string().optional().describe("For `show`: the commit/ref to inspect (default HEAD). For `log`: start from this ref."),
  maxCount: z.number().int().min(1).max(200).optional().describe("For `log`: maximum number of commits to return (default 20)."),
});

export const gitStatusTool: ToolDef<z.infer<typeof statusSchema>> = {
  name: "git_status",
  description:
    "Inspect the git repository at the working directory: `status` (working tree state), `diff` (unstaged or, with staged:true, " +
    "staged changes), `log` (recent commits), `show` (a specific commit/ref, default HEAD), or `branches` (local branches with " +
    "upstream tracking info). Read-only — runs automatically without confirmation.",
  schema: statusSchema,
  mutating: false,
  handler: async ({ operation, paths, staged, ref, maxCount }, ctx) => {
    const pathArgs = paths?.length ? ["--", ...paths] : [];
    const args: string[] = (() => {
      switch (operation) {
        case "status":
          return ["status", "--short", "--branch", ...pathArgs];
        case "diff":
          return ["diff", ...(staged ? ["--cached"] : []), ...pathArgs];
        case "log":
          return ["log", `--max-count=${maxCount ?? 20}`, "--oneline", "--decorate", ...(ref ? [ref] : [])];
        case "show":
          return ["show", ref ?? "HEAD"];
        case "branches":
          return ["branch", "--list", "-vv"];
      }
    })();

    const result = await runGit(args, ctx.cwd);
    if (result.exitCode !== 0) {
      return { error: truncate(result.stderr || result.stdout || `git ${operation} failed (exit ${result.exitCode})`) };
    }
    return { output: truncate(result.stdout) };
  },
};

// --- git_commit: mutating operations, gated behind a confirmation prompt ---

// Ref-like arguments (branch names, refs, remote names) are passed to git as bare positional
// args with no `--` separator. A value starting with `-` would otherwise be parsed by git as a
// flag instead of a ref/branch (e.g. ref: "--hard" turning a plain reset into a hard reset) —
// reject it at the schema boundary so it can never reach execa's argv.
function refLike(description: string) {
  return z
    .string()
    .refine((v) => !v.startsWith("-"), { message: 'must not start with "-" (would be parsed as a git flag, not a ref/branch name)' })
    .describe(description)
    .optional();
}

const commitSchema = z.object({
  operation: z.enum([
    "add",
    "commit",
    "create_branch",
    "checkout",
    "push",
    "reset",
    "stash",
    "merge",
    "rebase",
    "delete_branch",
  ]),
  paths: z.array(z.string()).optional().describe("For `add`: paths to stage. For `stash push`: paths to stash. Omit to stage all changes."),
  message: z.string().optional().describe("For `commit`: commit message. For `stash push`: stash message."),
  branchName: refLike("Branch name. Required for create_branch/checkout/merge/rebase/delete_branch."),
  createIfMissing: z.boolean().optional().describe("For `checkout`: create the branch if it doesn't exist yet (like `checkout -b`)."),
  remote: refLike('For `push`: remote name (default "origin").'),
  setUpstream: z.boolean().optional().describe("For `push`: set upstream tracking — needed the first time a new branch is pushed."),
  ref: refLike("For `reset`: ref to reset to (default HEAD). For `merge`/`rebase`: alternative ref if branchName omitted."),
  mode: z.enum(["soft", "mixed", "hard"]).optional().describe("For `reset`: reset mode (default mixed)."),
  strategy: z.enum(["fast-forward", "no-ff", "ff-only"]).optional().describe("For `merge`: merge strategy."),
  stashRef: refLike("For `stash pop`: stash reference (default stash@{0})."),
  force: z.boolean().optional().describe("For `delete_branch`: force delete an unmerged branch."),
});

export const gitCommitTool: ToolDef<z.infer<typeof commitSchema>> = {
  name: "git_commit",
  description:
    "Make changes to the git repository at the working directory: `add` (stage paths, or all changes if omitted), `commit` " +
    "(requires `message`; commit staged changes), `create_branch` (requires `branchName`; branch at current HEAD without switching), " +
    "`checkout` (requires `branchName`; switch branches, or create-and-switch with createIfMissing), `push` (push current branch), " +
    "`reset` (reset current branch; default mixed, default ref HEAD), `stash` (push or pop a stash), `merge` (merge branchName into " +
    "current branch), `rebase` (rebase current branch onto branchName), or `delete_branch` (requires `branchName`; delete a local branch). " +
    "Each mutating use requires the user's confirmation with a preview of the affected state.",
  schema: commitSchema,
  mutating: true,
  preview: async (args, ctx) => buildPreview(args, ctx.cwd),
  handler: async (args, ctx) => runMutatingOperation(args, ctx.cwd),
};

async function buildPreview(
  {
    operation,
    paths,
    message,
    branchName,
    createIfMissing,
    remote,
    setUpstream,
    ref,
    mode,
    strategy,
    stashRef,
    force,
  }: z.infer<typeof commitSchema>,
  cwd: string,
): Promise<string> {
  switch (operation) {
    case "add": {
      const target = paths?.length ? paths.join(", ") : "all changes";
      const status = await tryGit(["status", "--short", ...(paths?.length ? ["--", ...paths] : [])], cwd);
      return status ? `Stage ${target}:\n\n${status}` : `Stage ${target} (no changes detected).`;
    }
    case "commit": {
      const staged = await tryGit(["diff", "--cached"], cwd);
      if (!staged) return "Nothing is staged — this commit will fail. Use the `add` operation first.";
      return `Commit message: "${message ?? "(none provided — this will fail)"}"\n\n${staged}`;
    }
    case "create_branch":
      return `Create new branch "${branchName}" pointing at current HEAD (does not switch to it).`;
    case "checkout": {
      const status = await tryGit(["status", "--short"], cwd);
      const action = createIfMissing ? `Create and switch to new branch "${branchName}"` : `Switch to branch "${branchName}"`;
      return status ? `${action}.\n\nUncommitted changes that will carry over:\n${status}` : `${action}. Working tree is clean.`;
    }
    case "push": {
      const remoteName = remote ?? "origin";
      const branch = (await tryGit(["rev-parse", "--abbrev-ref", "HEAD"], cwd)).trim() || "HEAD";
      const ahead =
        (await tryGit(["log", "--oneline", "@{u}.."], cwd)) || (await tryGit(["log", "--oneline", "-n", "10"], cwd));
      const upstreamNote = setUpstream ? " (setting upstream tracking)" : "";
      return ahead
        ? `Push "${branch}" to "${remoteName}"${upstreamNote} — commits to push:\n\n${ahead}`
        : `Push "${branch}" to "${remoteName}"${upstreamNote}.`;
    }
    case "reset": {
      const targetRef = ref ?? "HEAD";
      const modeText = mode ?? "mixed";
      const diff = modeText === "hard" ? await tryGit(["diff", "--stat", "HEAD"], cwd) : await tryGit(["diff", "--cached", "--stat"], cwd);
      return `Reset (${modeText}) to ${targetRef}.${diff ? `\n\nFiles affected:\n${diff}` : ""}`;
    }
    case "stash": {
      if (stashRef) {
        const stash = await tryGit(["stash", "show", "-p", stashRef], cwd);
        return stash ? `Pop stash ${stashRef}:\n\n${stash}` : `Pop stash ${stashRef}.`;
      }
      const status = await tryGit(["status", "--short", ...(paths?.length ? ["--", ...paths] : [])], cwd);
      return status
        ? `Stash ${message ? `"${message}"` : "changes"}${paths?.length ? ` (paths: ${paths.join(", ")})` : ""}:\n\n${status}`
        : "No local changes to stash.";
    }
    case "merge": {
      const into = (await tryGit(["rev-parse", "--abbrev-ref", "HEAD"], cwd)).trim() || "HEAD";
      const target = branchName ?? ref;
      const log = target ? await tryGit(["log", "--oneline", `${into}..${target}`], cwd) : "";
      return target
        ? `Merge "${target}" into "${into}"${strategy ? ` (strategy: ${strategy})` : ""}.${log ? `\n\nCommits to merge:\n${log}` : ""}`
        : "merge requires `branchName` or `ref`.";
    }
    case "rebase": {
      const onto = branchName ?? ref;
      const current = (await tryGit(["rev-parse", "--abbrev-ref", "HEAD"], cwd)).trim() || "HEAD";
      const log = onto ? await tryGit(["log", "--oneline", `${onto}..${current}`], cwd) : "";
      return onto
        ? `Rebase "${current}" onto "${onto}".${log ? `\n\nCommits that will be replayed:\n${log}` : ""}`
        : "rebase requires `branchName` or `ref`.";
    }
    case "delete_branch": {
      const log = branchName ? await tryGit(["log", "--oneline", `${branchName}..HEAD`], cwd) : "";
      const note = force ? " (force delete)" : "";
      return branchName
        ? `Delete local branch "${branchName}"${note}.${log ? `\n\nCommits on ${branchName} not in HEAD:\n${log}` : ""}`
        : "delete_branch requires `branchName`.";
    }
  }
}

async function runMutatingOperation(args: z.infer<typeof commitSchema>, cwd: string): Promise<unknown> {
  const {
    operation,
    paths,
    message,
    branchName,
    createIfMissing,
    remote,
    setUpstream,
    ref,
    mode,
    strategy,
    stashRef,
    force,
  } = args;

  const gitArgs: string[] = (() => {
    switch (operation) {
      case "add":
        return ["add", ...(paths?.length ? paths : ["-A"])];
      case "commit": {
        if (!message) throw new Error("`message` is required for the commit operation.");
        return ["commit", "-m", message];
      }
      case "create_branch": {
        if (!branchName) throw new Error("`branchName` is required for the create_branch operation.");
        return ["branch", branchName];
      }
      case "checkout": {
        if (!branchName) throw new Error("`branchName` is required for the checkout operation.");
        return createIfMissing ? ["checkout", "-b", branchName] : ["checkout", branchName];
      }
      case "push":
        return ["push", ...(setUpstream ? ["-u"] : []), remote ?? "origin", "HEAD"];
      case "reset": {
        const targetRef = ref ?? "HEAD";
        return ["reset", ...(mode ? [`--${mode}`] : []), targetRef];
      }
      case "stash": {
        if (stashRef) {
          return ["stash", "pop", stashRef];
        }
        const stashArgs = ["stash", "push"];
        if (message) stashArgs.push("-m", message);
        if (paths?.length) stashArgs.push("--", ...paths);
        return stashArgs;
      }
      case "merge": {
        const target = branchName ?? ref;
        if (!target) throw new Error("`merge` requires `branchName` or `ref`.");
        const mergeArgs = ["merge"];
        if (strategy === "no-ff") mergeArgs.push("--no-ff");
        if (strategy === "ff-only") mergeArgs.push("--ff-only");
        mergeArgs.push(target);
        return mergeArgs;
      }
      case "rebase": {
        const onto = branchName ?? ref;
        if (!onto) throw new Error("`rebase` requires `branchName` or `ref`.");
        return ["rebase", onto];
      }
      case "delete_branch": {
        if (!branchName) throw new Error("`branchName` is required for the delete_branch operation.");
        return ["branch", force ? "-D" : "-d", branchName];
      }
    }
  })();

  const result = await runGit(gitArgs, cwd);
  if (result.exitCode !== 0) {
    return { error: truncate(result.stderr || result.stdout || `git ${operation} failed (exit ${result.exitCode})`) };
  }
  const output = truncate(result.stdout || result.stderr);

  switch (operation) {
    case "add":
      return { staged: paths?.length ? paths : ["(all changes)"] };
    case "create_branch":
      return { created: branchName };
    case "checkout":
      return { switchedTo: branchName };
    case "reset":
      return { resetTo: ref ?? "HEAD", mode: mode ?? "mixed" };
    case "stash":
      return stashRef ? { popped: stashRef } : { stashed: message ?? "(no message)" };
    case "merge":
      return { merged: branchName ?? ref, output };
    case "rebase":
      return { rebasedOnto: branchName ?? ref, output };
    case "delete_branch":
      return { deleted: branchName };
    default:
      return { output };
  }
}