package api

import (
	"context"
	"database/sql"
	"errors"
	"net/http"
	"net/url"
	"time"

	"git.misaka.ren/m1saka/dsh-web/internal/docker"
)

func (a *API) deleteImage(w http.ResponseWriter, r *http.Request) {
	u, _, err := a.user(r)
	if err != nil {
		fail(w, 401, "authentication required")
		return
	}
	if !u.Admin {
		fail(w, 403, "administrator required")
		return
	}
	id := r.URL.Query().Get("image_id")
	if !runtimeImageID.MatchString(id) {
		fail(w, 400, "invalid image_id")
		return
	}
	// Upgrades also acquire a.mu before buildQueue. Keep both through deletion.
	a.mu.Lock()
	defer a.mu.Unlock()
	buildQueue.Lock()
	defer buildQueue.Unlock()
	if buildQueue.active[a.s.DB] {
		fail(w, 409, "image build worker is active")
		return
	}
	ctx, cancel := context.WithTimeout(r.Context(), 30*time.Second)
	defer cancel()
	tx, err := a.s.DB.BeginTx(ctx, nil)
	if err != nil {
		fail(w, 500, "database error")
		return
	}
	defer tx.Rollback()
	// Take SQLite's writer lock before checking intents: reservation does not use a.mu.
	if _, err = tx.ExecContext(ctx, "UPDATE images SET status=status WHERE image_id=?", id); err != nil {
		fail(w, 500, "image index unavailable")
		return
	}
	var version string
	err = tx.QueryRowContext(ctx, "SELECT version FROM images WHERE image_id=?", id).Scan(&version)
	if errors.Is(err, sql.ErrNoRows) {
		fail(w, 404, "managed image not found")
		return
	}
	if err != nil {
		fail(w, 500, "image index unavailable")
		return
	}
	for _, check := range []struct{ table, query string }{
		{"image_builds", "SELECT count(*) FROM image_builds WHERE status IN ('queued','running','validating')"},
		{"creation_intents", "SELECT count(*) FROM creation_intents WHERE status IN ('waiting','creating')"},
		{"upgrade_journal", "SELECT count(*) FROM upgrade_journal WHERE phase NOT IN ('complete','rolled_back')"},
	} {
		var exists, count int
		if err = tx.QueryRowContext(ctx, "SELECT count(*) FROM sqlite_master WHERE type='table' AND name=?", check.table).Scan(&exists); err == nil && exists > 0 {
			err = tx.QueryRowContext(ctx, check.query).Scan(&count)
		}
		if err != nil {
			fail(w, 500, "active task lookup failed")
			return
		}
		if count > 0 {
			fail(w, 409, "active task prevents image deletion")
			return
		}
	}
	var references int
	if err = tx.QueryRowContext(ctx, "SELECT count(*) FROM instances WHERE image_id=?", id).Scan(&references); err != nil {
		fail(w, 500, "instance reference lookup failed")
		return
	}
	if references > 0 {
		fail(w, 409, "image is referenced by an instance")
		return
	}
	var image struct {
		ID     string `json:"Id"`
		Config struct{ Labels map[string]string }
	}
	path := "/images/" + url.PathEscape(id)
	if err = a.docker.Do(ctx, http.MethodGet, path+"/json", nil, &image); err != nil {
		fail(w, 502, "image inspection failed")
		return
	}
	if image.ID != id || image.Config.Labels["dsh-mgr.role"] != "runtime" || version == "" || image.Config.Labels["dsh-mgr.version"] != version {
		fail(w, 409, "managed runtime image required")
		return
	}
	var containers []struct{ ImageID string }
	if err = a.docker.Do(ctx, http.MethodGet, "/containers/json?all=1", nil, &containers); err != nil || containers == nil {
		fail(w, 502, "container reference lookup failed")
		return
	}
	for _, container := range containers {
		if container.ImageID == "" {
			fail(w, 502, "container image identity unavailable")
			return
		}
		if container.ImageID == id {
			fail(w, 409, "image is referenced by a container")
			return
		}
	}
	if _, err = tx.ExecContext(ctx, "UPDATE images SET status='missing',usage_count=0 WHERE image_id=?", id); err == nil {
		_, err = tx.ExecContext(ctx, "UPDATE image_builds SET status='missing',error='image deleted by administrator' WHERE image_id=? AND status='success'", id)
	}
	if err == nil {
		_, err = tx.ExecContext(ctx, "INSERT INTO audit(uid,action,target,detail,at) VALUES(?,'image.delete',?,'',?)", u.ID, id, time.Now().Unix())
	}
	if err != nil {
		fail(w, 500, "image deletion recording failed")
		return
	}
	if err = a.docker.Do(ctx, http.MethodDelete, path+"?force=false", nil, nil); err != nil {
		status := http.StatusBadGateway
		var apiErr *docker.APIError
		if errors.As(err, &apiErr) && apiErr.StatusCode == http.StatusConflict {
			status = http.StatusConflict
		}
		fail(w, status, "docker image deletion failed")
		return
	}
	if err = tx.Commit(); err != nil {
		fail(w, 500, "image deleted but recording failed")
		return
	}
	writeJSON(w, map[string]string{"image_id": id, "status": "missing"})
}