package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/novox/mesh-controller/internal/builder"
	"github.com/novox/mesh-controller/internal/catalogue"
	"github.com/novox/mesh-controller/internal/link"
)

// `check-here` is a pull request's merge check run on the machine at hand **exactly as the build seat
// runs it** (novox/hq issue 283): the same code (builder.Check), the same ask the controller would make of
// the seat — the gate's modules and judge by the planner's own answer over the facts snapshot, the
// repositories beside it at the refs the snapshot says the seat clones them at — in the toolchain image
// the mesh holds, as the user the build seat runs as, against a throwaway store and bus of the versions
// the mesh runs.
//
// **The build seat is the reference.** A merge-check.sh that passed on an agent's machine failed on the
// seat for three reasons that were each the agent's environment, never the change: a newer Go whose gofmt
// lays a file out differently, a sibling checkout at the agent's feature branch where the seat had the
// commit the mesh runs, and a different user. Run here, a check sees what the seat will.
//
//	check-here [--tree <checkout>] [--base main] [--registry <artifact store>] [--forge <url of the owner>]
//	           [--number <n>] [--user uid:gid] [--facts store|<file>] [--keep]
//
// The checkout's HEAD is what is checked, and it must be committed: the seat checks a commit, never a
// working tree.
func checkHereCommand(ctx context.Context, args []string) error {
	set := flag.NewFlagSet("check-here", flag.ContinueOnError)
	tree := set.String("tree", ".", "the change's checkout; its HEAD is checked")
	base := set.String("base", "main", "the branch the change would merge into")
	registry := set.String("registry", os.Getenv("MESH_REGISTRY"), "the artifact store holding the facts and the toolchains")
	forge := set.String("forge", "", "where the repositories beside it are cloned from, as <forge>/<repository>.git; "+
		"the checkout's origin without its own name when not given")
	number := set.Int("number", 0, "the pull request's number, when there is one")
	// The build seat's service runs as root, and its check containers run as the builder does.
	user := set.String("user", "0:0", "the user the check's containers run as: the build seat's")
	keep := set.Bool("keep", false, "keep the workspace afterwards")
	factsFrom := set.String("facts", "store", "the facts snapshot: `store`, the one the artifact store holds — "+
		"what the seat reads — or a file")
	if _, err := parseAround(set, args); err != nil {
		return err
	}
	if *registry == "" {
		return errors.New("check-here reads the facts and the toolchains from the artifact store: --registry <host:port> or MESH_REGISTRY")
	}
	dir, err := filepath.Abs(*tree)
	if err != nil {
		return err
	}
	git := func(args ...string) (string, error) {
		cmd := exec.CommandContext(ctx, "git", args...)
		cmd.Dir = dir
		out, err := cmd.Output()
		return strings.TrimSpace(string(out)), err
	}
	if dirty, err := git("status", "--porcelain", "--untracked-files=no"); err != nil {
		return fmt.Errorf("%s is not a checkout: %w", dir, err)
	} else if dirty != "" {
		return errors.New("the checkout has changes not committed: the build seat checks a commit, so commit first")
	}
	head, err := git("rev-parse", "HEAD")
	if err != nil {
		return err
	}
	origin, err := git("remote", "get-url", "origin")
	if err != nil {
		return fmt.Errorf("the checkout has no origin to say which repository it is: %w", err)
	}
	owner, repo, prefix := ownerRepoOf(origin)
	if *forge == "" {
		*forge = prefix
	}
	if _, err := git("fetch", "--quiet", "origin", *base); err != nil {
		return fmt.Errorf("cannot fetch %s to say what the change touches: %w", *base, err)
	}
	changedText, err := git("diff", "--name-only", "origin/"+*base+"...HEAD")
	if err != nil {
		return err
	}
	var paths, removed []string
	for _, p := range strings.Split(changedText, "\n") {
		if p = strings.TrimSpace(p); p == "" {
			continue
		}
		paths = append(paths, p)
		if _, err := os.Stat(filepath.Join(dir, p)); os.IsNotExist(err) {
			removed = append(removed, p)
		}
	}

	_ = os.Setenv("MESH_REGISTRY", *registry)
	f, err := readFacts(ctx, *factsFrom)
	if err != nil {
		return fmt.Errorf("the facts snapshot cannot be read: %w", err)
	}
	entries, read, edges, err := graphOfFacts(f)
	if err != nil {
		return err
	}
	p := link.PullUpdated{Owner: owner, Repo: repo, Number: *number, Base: *base, Commit: head, Paths: paths,
		Removed: removed, ModuleDirs: moduleDirsIn(dir, paths), ModuleDirsSaid: true}
	scope := pullScope(p, entries, read, edges)
	_, scriptErr := os.Stat(filepath.Join(dir, builder.CheckScript))
	if !scope.gated() && !scope.Mesh {
		fmt.Printf("%s: %s, and the repository is not the mesh's: the build seat runs nothing for it\n",
			owner+"/"+repo, noModuleTouched)
		return nil
	}
	if !scope.gated() && scriptErr != nil {
		fmt.Printf("%s: %s; %s\n", owner+"/"+repo, noModuleTouched, noMergeCheck)
		return nil
	}

	toolchains := map[string]string{}
	for language, reference := range f.Versions.Toolchains {
		toolchains[language] = catalogue.Rerouted(reference, *registry)
	}
	if len(toolchains) == 0 {
		return errors.New("the facts snapshot names no toolchain: it was taken by a controller from before " +
			"issue 283, and the seat's toolchain cannot be known here")
	}
	beside := map[string]builder.Beside{}
	for d, ref := range f.Beside {
		from := d
		if d == "mesh-controller-main" {
			from = "mesh-controller"
		}
		beside[d] = builder.Beside{Repository: strings.TrimSuffix(*forge, "/") + "/" + from + ".git", Ref: ref}
	}
	id := fmt.Sprintf("check-here-%d", time.Now().UnixNano())
	spec := builder.CheckSpec{ID: id, Repository: dir, Ref: head, Owner: owner, Repo: repo, Number: *number,
		Paths: paths, Beside: beside, Modules: scope.Modules, New: scope.New, Manifests: scope.Manifests,
		Base: *base, Judge: scope.Judge, Toolchain: toolchains["go"], Toolchains: toolchains, User: *user}

	workspace, err := os.MkdirTemp("", "mesh-check-here-")
	if err != nil {
		return err
	}
	if !*keep {
		defer removeWorkspace(spec.Toolchain, workspace, *user)
	}
	fmt.Fprintf(os.Stderr, "checking %s/%s at %.8s as the build seat would, against the facts of %s, in %s\n",
		owner, repo, head, f.Taken.Format(time.RFC3339), workspace)
	v, err := builder.Check(ctx, builder.Command, spec, workspace, *registry, builder.GitCredential{},
		func(step, message string) {
			if step != "output" {
				fmt.Fprintf(os.Stderr, "  [%s] %s\n", step, message)
			}
		})
	if err != nil {
		return fmt.Errorf("the check could not run — on the seat an error, never a pass: %w", err)
	}
	fmt.Println(v.Report)
	fmt.Println()
	fmt.Printf("mesh/merge-gate: %s — %s\n", strings.ToUpper(v.Gate.Verdict), v.Gate.Summary)
	if v.Repo != nil {
		fmt.Printf("mesh/repo-check: %s — %s\n", strings.ToUpper(v.Repo.Verdict), v.Repo.Summary)
	}
	for _, l := range []*builder.Layer{v.Gate, v.Repo} {
		if l != nil && l.Verdict != "pass" && l.Verdict != "warning" {
			return errors.New("the build seat would not pass this change")
		}
	}
	return nil
}

// ownerRepoOf reads owner, repository and the owner's URL from a remote: ssh://git@host:222/novox/mesh-host.git
// → novox, mesh-host, ssh://git@host:222/novox.
func ownerRepoOf(remote string) (string, string, string) {
	trimmed := strings.TrimSuffix(strings.TrimSuffix(remote, "/"), ".git")
	cut := strings.LastIndexAny(trimmed, "/:")
	if cut < 0 {
		return "", trimmed, ""
	}
	repo, prefix := trimmed[cut+1:], trimmed[:cut]
	owner := prefix
	if at := strings.LastIndexAny(prefix, "/:"); at >= 0 {
		owner = prefix[at+1:]
	}
	return owner, repo, prefix
}

// removeWorkspace removes what the check left, written as the seat's user: by a container of that user
// when it is not this one.
func removeWorkspace(image, workspace, user string) {
	if image != "" && user != fmt.Sprintf("%d:%d", os.Getuid(), os.Getgid()) {
		// Everything in it — the check's HOME is the workspace, so the toolchain's own files are there too.
		_ = exec.Command("docker", "run", "--rm", "--user", user, "--volume", workspace+":/workspace", image,
			"sh", "-c", "rm -rf /workspace/* /workspace/.[!.]*").Run()
	}
	_ = os.RemoveAll(workspace)
}