// Copyright 2026 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"context"
	"flag"
	"fmt"
	"io"

	"golang.org/x/pkgsite/cmd/internal/pkgsite-cli/client"
	"golang.org/x/sync/errgroup"
)

func runModule(fs *flag.FlagSet, m *moduleFlags, stdout, stderr io.Writer) int {
	if fs.NArg() != 1 {
		fmt.Fprintf(stderr, "Error: expected exactly 1 module argument, got %d\n", fs.NArg())
		fs.Usage()
		return 2
	}
	path, version := splitPathVersion(fs.Arg(0))

	ctx, cancel := context.WithTimeout(context.Background(), m.timeout)
	defer cancel()

	c, err := client.New(m.server)
	if err != nil {
		handleErr(stdout, stderr, err, m.jsonOut)
		return 1
	}
	c.PrintURLs = m.printURLs
	c.Output = stderr
	mod, err := c.GetModule(ctx, path, version, client.ModuleOptions{
		Readme:   m.readme,
		Licenses: m.licenses,
	})
	if err != nil {
		handleErr(stdout, stderr, err, m.jsonOut)
		return 1
	}
	result := moduleResult{Module: mod}

	var (
		vers  *client.PaginatedResponse[client.VersionResponse]
		vulns *client.PaginatedResponse[client.Vulnerability]
		pkgs  *client.PaginatedResponse[client.ModulePackageResponse]
	)

	g, gctx := errgroup.WithContext(ctx)

	if m.versions {
		g.Go(func() error {
			fetch := func(token string, limit int) (*client.PaginatedResponse[client.VersionResponse], error) {
				// Pass limit to API to limit server-side page size.
				return c.GetVersions(gctx, path, client.PaginationOptions{
					Limit: limit,
					Token: token,
				})
			}
			// Pass limit to AllItems to stop fetching when limit is reached.
			items, total, nextToken, err := client.AllItems(m.versionsToken, m.effectiveLimit(), fetch)
			if err != nil {
				if client.Is429(err) {
					vers = &client.PaginatedResponse[client.VersionResponse]{
						Items:         items,
						Total:         total,
						NextPageToken: nextToken,
					}
				}
				return err
			}
			vers = &client.PaginatedResponse[client.VersionResponse]{
				Items: items,
				Total: total,
			}
			return nil
		})
	}
	if m.vulns {
		g.Go(func() error {
			fetch := func(token string, limit int) (*client.PaginatedResponse[client.Vulnerability], error) {
				// Pass limit to API to limit server-side page size.
				return c.GetVulns(gctx, path, version, client.PaginationOptions{
					Limit: limit,
					Token: token,
				})
			}
			// Pass limit to AllItems to stop fetching when limit is reached.
			items, total, nextToken, err := client.AllItems(m.vulnsToken, m.effectiveLimit(), fetch)
			if err != nil {
				if client.Is429(err) {
					vulns = &client.PaginatedResponse[client.Vulnerability]{
						Items:         items,
						Total:         total,
						NextPageToken: nextToken,
					}
				}
				return err
			}
			vulns = &client.PaginatedResponse[client.Vulnerability]{
				Items: items,
				Total: total,
			}
			return nil
		})
	}
	if m.packages {
		g.Go(func() error {
			fetch := func(token string, limit int) (*client.PaginatedResponse[client.ModulePackageResponse], error) {
				// Pass limit to API to limit server-side page size.
				return c.GetPackages(gctx, path, version, client.PaginationOptions{
					Limit: limit,
					Token: token,
				})
			}
			// Pass limit to AllItems to stop fetching when limit is reached.
			items, total, nextToken, err := client.AllItems(m.packagesToken, m.effectiveLimit(), fetch)
			if err != nil {
				if client.Is429(err) {
					pkgs = &client.PaginatedResponse[client.ModulePackageResponse]{
						Items:         items,
						Total:         total,
						NextPageToken: nextToken,
					}
				}
				return err
			}
			pkgs = &client.PaginatedResponse[client.ModulePackageResponse]{
				Items: items,
				Total: total,
			}
			return nil
		})
	}

	if err := g.Wait(); err != nil {
		if client.Is429(err) {
			result.Versions = vers
			result.Vulns = vulns
			result.Packages = pkgs
			return printPartialModuleResult(stdout, stderr, result, m.jsonOut)
		}
		handleErr(stdout, stderr, err, m.jsonOut)
		return 1
	}

	result.Versions = vers
	result.Vulns = vulns
	result.Packages = pkgs

	if m.jsonOut {
		return writeJSON(stdout, stderr, result)
	}
	formatModule(stdout, result)
	return 0
}

// moduleFlags are flags for the module subcommand.
type moduleFlags struct {
	commonFlags
	readme        bool
	licenses      bool
	versions      bool
	vulns         bool
	packages      bool
	versionsToken string
	vulnsToken    string
	packagesToken string
}

func (f *moduleFlags) register(fs *flag.FlagSet) {
	f.commonFlags.register(fs)
	fs.BoolVar(&f.readme, "readme", false, "include README")
	fs.BoolVar(&f.licenses, "licenses", false, "show license information")
	fs.BoolVar(&f.versions, "versions", false, "list versions")
	fs.BoolVar(&f.vulns, "vulns", false, "list vulnerabilities")
	fs.BoolVar(&f.packages, "packages", false, "list packages")
	fs.StringVar(&f.versionsToken, "versions-token", "", "page token for versions pagination")
	fs.StringVar(&f.vulnsToken, "vulns-token", "", "page token for vulns pagination")
	fs.StringVar(&f.packagesToken, "packages-token", "", "page token for packages pagination")
}

func printPartialModuleResult(stdout, stderr io.Writer, result moduleResult, jsonMode bool) int {
	if jsonMode {
		writeJSON(stdout, stderr, result)
	} else {
		formatModule(stdout, result)
		fmt.Fprintln(stderr, "Warning: hit rate limit (429); results are incomplete.")
	}
	return 1
}