package main

import (
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"
	"unicode/utf8"

	sdk "code.gitea.io/sdk/gitea"

	"git.noodles.cam/claude-skills/marketplace/cli/internal/config"
	"git.noodles.cam/claude-skills/marketplace/cli/internal/gitea"
)

const (
	// userAgent names this tool in the instance's log. An admin looking at a
	// burst of requests should be able to tell a release from a push.
	userAgent = "kettle-release"
	// requestTimeout bounds one call. Generous next to the transport's 30s
	// because one of these calls is an upload: a 20 MB binary over a domestic
	// connection is minutes, and a run that gives up half way through its
	// assets is exactly the mess this tool exists to avoid.
	requestTimeout = 10 * time.Minute
	// pageLimit and maxPages bound the two listings this makes. A repository
	// with a runaway number of releases must not turn one publish into an
	// unbounded read.
	pageLimit = 50
	maxPages  = 20
)

// spec is what was asked for: one release, and the files that belong on it.
type spec struct {
	Tag        string
	Title      string
	Notes      string
	Target     string
	Draft      bool
	Prerelease bool
	Files      []string
}

// title defaults to the tag, because Gitea refuses a release without one and
// "v1.2.3" is what a person would have typed anyway.
func (s spec) title() string {
	if s.Title != "" {
		return s.Title
	}
	return s.Tag
}

// asset is one file that ended up on the release.
type asset struct {
	Name string
	URL  string
	// Replaced records that an attachment of this name was already there and
	// was removed to make room. Two assets with one name is the failure mode a
	// retried publish has, and it is silent: the download URL is by name.
	Replaced bool
}

// receipt is what happened, in the words the run will print.
type receipt struct {
	Repo    string
	Release *sdk.Release
	// State is "created", "updated" or "reused" — which of the three a re-run
	// hit is the whole question an operator has about idempotency.
	State  string
	Assets []asset
}

// publish makes the tracker say what the spec says, and reports what it did.
func publish(cfg *config.Resolved, s spec) (*receipt, error) {
	c, err := newClient(cfg)
	if err != nil {
		return nil, err
	}

	rel, state, err := c.releaseFor(s)
	if err != nil {
		return nil, err
	}
	assets, err := c.uploadAll(rel, s.Files)
	if err != nil {
		return nil, err
	}
	return &receipt{Repo: c.slug(), Release: rel, State: state, Assets: assets}, nil
}

// print writes the receipt: what happened to the release, every asset that
// ended up on it, and the URL a person opens.
func (r *receipt) print(w io.Writer) {
	fmt.Fprintf(w, "%-9s release %s in %s\n", r.State, r.Release.TagName, r.Repo)

	width := 0
	for _, a := range r.Assets {
		if n := utf8.RuneCountInString(a.Name); n > width {
			width = n
		}
	}
	uploaded, replaced := 0, 0
	for _, a := range r.Assets {
		verb := "uploaded"
		uploaded++
		if a.Replaced {
			verb, replaced = "replaced", replaced+1
		}
		fmt.Fprintf(w, "%-9s %-*s  %s\n", verb, width, a.Name, a.URL)
	}

	if url := r.Release.HTMLURL; url != "" {
		fmt.Fprintf(w, "%-9s %s\n", "release", url)
	}
	fmt.Fprintf(w, "%d asset(s): %d uploaded, %d replaced — draft: %s, prerelease: %s\n",
		len(r.Assets), uploaded-replaced, replaced,
		yesNo(r.Release.IsDraft), yesNo(r.Release.IsPrerelease))
}

func yesNo(b bool) string {
	if b {
		return "yes"
	}
	return "no"
}

// client is one repository on one instance.
type client struct {
	api         *sdk.Client
	owner, name string
}

func (c *client) slug() string { return c.owner + "/" + c.name }

// newClient refuses a half-filled configuration before it dials, the same way
// gitea.New does and for the same reason: building a client is itself a
// request — the SDK asks the instance for its version before it hands one back
// — and a missing token reported as a connection failure sends whoever is
// reading it to the wrong place.
func newClient(cfg *config.Resolved) (*client, error) {
	if cfg == nil {
		return nil, errors.New("no resolved configuration — call config.ResolveOutsideAProject first")
	}
	if err := cfg.Complete(); err != nil {
		return nil, err
	}

	base := strings.TrimRight(cfg.URL, "/")
	api, err := sdk.NewClient(base,
		sdk.SetToken(cfg.Token),
		sdk.SetHTTPClient(&http.Client{Timeout: requestTimeout}),
		sdk.SetUserAgent(userAgent))
	if err != nil {
		if errors.Is(err, &sdk.ErrUnknownVersion{}) {
			return nil, fmt.Errorf("%s did not answer with a version this can read (%w)"+
				" — check that %s points at a Gitea instance", base, err, config.EnvURL)
		}
		return nil, fmt.Errorf("cannot reach the Gitea instance at %s: %w", base, err)
	}
	return &client{api: api, owner: cfg.Owner, name: cfg.Repo}, nil
}

// releaseFor is the release this tag should have, created or brought into line.
func (c *client) releaseFor(s spec) (*sdk.Release, string, error) {
	found, err := c.find(s.Tag)
	if err != nil {
		return nil, "", err
	}
	if found == nil {
		rel, err := c.create(s)
		return rel, "created", err
	}
	rel, changed, err := c.converge(found, s)
	if err != nil {
		return nil, "", err
	}
	if changed {
		return rel, "updated", nil
	}
	return rel, "reused", nil
}

// find is the release for this tag, or nil when the repository has none.
//
// A 404 is an answer here and not a failure — it is what "no release yet"
// looks like, which is the ordinary case the first time a tag is published.
// Anything else is reported, because "the instance refused us" and "there is
// nothing there" must not both read as "create one".
func (c *client) find(tag string) (*sdk.Release, error) {
	got, resp, err := c.api.GetReleaseByTag(c.owner, c.name, tag)
	if err == nil {
		return got, nil
	}
	if failed := gitea.Fail(resp, err); !gitea.StatusIs(failed, http.StatusNotFound) {
		return nil, fmt.Errorf("looking for a release on %s: %w", tag, failed)
	}
	// The by-tag route is a lookup through the tag, and a draft need not have
	// one — so a draft this tool created on an earlier run can answer 404 to
	// the question "is it already there?". Scanning the listing is what keeps a
	// retried `--draft` publish from filing a second release for one tag.
	return c.scan(tag)
}

// scan walks the release listing for this tag.
func (c *client) scan(tag string) (*sdk.Release, error) {
	for page := 1; page <= maxPages; page++ {
		batch, resp, err := c.api.ListReleases(c.owner, c.name, sdk.ListReleasesOptions{
			ListOptions: sdk.ListOptions{Page: page, PageSize: pageLimit},
		})
		if err := gitea.Fail(resp, err); err != nil {
			return nil, fmt.Errorf("listing releases: %w", err)
		}
		for _, rel := range batch {
			if rel.TagName == tag {
				return rel, nil
			}
		}
		if len(batch) < pageLimit {
			return nil, nil // a short page is the last one
		}
	}
	return nil, nil
}

func (c *client) create(s spec) (*sdk.Release, error) {
	got, resp, err := c.api.CreateRelease(c.owner, c.name, sdk.CreateReleaseOption{
		TagName:      s.Tag,
		Target:       s.Target,
		Title:        s.title(),
		Note:         s.Notes,
		IsDraft:      s.Draft,
		IsPrerelease: s.Prerelease,
	})
	if err := gitea.Fail(resp, err); err != nil {
		return nil, fmt.Errorf("creating the release for %s: %w", s.Tag, err)
	}
	if got == nil || got.ID == 0 {
		return nil, fmt.Errorf("creating the release for %s: the tracker's answer carries no id", s.Tag)
	}
	return got, nil
}

// converge edits an existing release until it says what the spec says, and
// reports whether anything had to change.
//
// Reuse alone would be enough to make a re-run not fail; it would not make it
// CONVERGE. A second run with corrected notes has to leave the release holding
// the corrected notes, or the retry that fixed the mistake published the
// mistake again.
//
// Empty notes mean "leave what is there", not "clear them": `--notes-file` is
// how notes are supplied, and a run that did not supply any is not a run asking
// for the release to be emptied.
func (c *client) converge(rel *sdk.Release, s spec) (*sdk.Release, bool, error) {
	note := s.Notes
	if note == "" {
		note = rel.Note
	}
	if rel.Title == s.title() && rel.Note == note &&
		rel.IsDraft == s.Draft && rel.IsPrerelease == s.Prerelease {
		return rel, false, nil
	}

	draft, prerelease := s.Draft, s.Prerelease
	got, resp, err := c.api.EditRelease(c.owner, c.name, rel.ID, sdk.EditReleaseOption{
		TagName:      rel.TagName,
		Title:        s.title(),
		Note:         note,
		IsDraft:      &draft,
		IsPrerelease: &prerelease,
	})
	if err := gitea.Fail(resp, err); err != nil {
		return nil, false, fmt.Errorf("updating the release for %s: %w", rel.TagName, err)
	}
	if got == nil || got.ID == 0 {
		return nil, false, fmt.Errorf("updating the release for %s: the tracker's answer carries no id", rel.TagName)
	}
	return got, true, nil
}

// uploadAll puts every named file on the release, replacing an attachment that
// already carries that name.
//
// The listing is read once, before the first upload, because the names that
// matter are the ones that were there when the run started: the files being
// uploaded are checked for duplicate basenames up front, so nothing this run
// adds can collide with something else this run adds.
func (c *client) uploadAll(rel *sdk.Release, files []string) ([]asset, error) {
	if len(files) == 0 {
		return nil, nil
	}
	existing, err := c.attachments(rel.ID)
	if err != nil {
		return nil, err
	}
	byName := map[string][]*sdk.Attachment{}
	for _, a := range existing {
		byName[a.Name] = append(byName[a.Name], a)
	}

	out := make([]asset, 0, len(files))
	for _, path := range files {
		name := filepath.Base(path)
		replaced := false
		// Removed before the upload rather than after it. Gitea will happily
		// hold two attachments with one name, and the download URL names the
		// file — so the state to avoid at all costs is the ambiguous one, not
		// the momentarily absent one.
		for _, old := range byName[name] {
			if resp, err := c.api.DeleteReleaseAttachment(c.owner, c.name, rel.ID, old.ID); err != nil {
				return out, fmt.Errorf("removing the old %s: %w", name, gitea.Fail(resp, err))
			}
			replaced = true
		}
		got, err := c.upload(rel.ID, path, name)
		if err != nil {
			return out, err
		}
		out = append(out, asset{Name: name, URL: got.DownloadURL, Replaced: replaced})
	}
	return out, nil
}

func (c *client) attachments(release int64) ([]*sdk.Attachment, error) {
	var out []*sdk.Attachment
	for page := 1; page <= maxPages; page++ {
		batch, resp, err := c.api.ListReleaseAttachments(c.owner, c.name, release,
			sdk.ListReleaseAttachmentsOptions{ListOptions: sdk.ListOptions{Page: page, PageSize: pageLimit}})
		if err := gitea.Fail(resp, err); err != nil {
			return nil, fmt.Errorf("listing the release's assets: %w", err)
		}
		out = append(out, batch...)
		if len(batch) < pageLimit {
			return out, nil
		}
	}
	return out, nil
}

func (c *client) upload(release int64, path, name string) (*sdk.Attachment, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("uploading %s: %w", name, err)
	}
	defer f.Close()

	got, resp, err := c.api.CreateReleaseAttachment(c.owner, c.name, release, f, name)
	if err := gitea.Fail(resp, err); err != nil {
		return nil, fmt.Errorf("uploading %s: %w", name, err)
	}
	if got == nil {
		return nil, fmt.Errorf("uploading %s: the tracker's answer carries no attachment", name)
	}
	return got, nil
}