package api

import (
	"fmt"
	"net/http"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/appbackup"
	"gitea.dooplex.hu/admin/felhom-controller/internal/backup"
	"gitea.dooplex.hu/admin/felhom-controller/internal/stacks"
)

// keptChoiceData is what the install page needs to ask the household (`09` §3 decision 36). The
// sentences come rendered in the request's language; the page shows them as they are.
type keptChoiceData struct {
	Code       string `json:"code"` // "kept_data_choice"
	Title      string `json:"title"`
	Body       string `json:"body"`
	UseLabel   string `json:"use_label"`
	UseDesc    string `json:"use_desc"`    // "" when use is off
	UseOff     string `json:"use_off"`     // "" when use is offered
	UseOffered bool   `json:"use_offered"` // a database copy exists for these files
	FreshLabel string `json:"fresh_label"`
	FreshDesc  string `json:"fresh_desc"`
	NotBacked  string `json:"not_backed_up"`
}

// keptDataAtInstall answers the install when the app's private drive folder already holds data:
//
//   - no choice → 409 kept_data_choice with the sentences (nothing moved, nothing installed);
//   - "use"     → a LOAD from the newest usable copy (backup.KeptBestCopy: own unit, second drive, or —
//     R-691 (2) — the off-site copy, downloaded unit-only at load time), then the app's after_load; 202.
//     The page names the copy and its date. Refused 409 with use_off when no copy exists;
//   - "fresh"   → not handled here: DeployStack moves the old data aside and installs.
//
// Returns true when it wrote the response.
func (r *Router) keptDataAtInstall(w http.ResponseWriter, req *http.Request, name, hdd, choice string) bool {
	old := r.stackMgr.OldAppData(name, hdd)
	if len(old) == 0 || choice == stacks.KeptChoiceFresh {
		return false
	}
	display := name
	if st, ok := r.stackMgr.GetStack(name); ok && st.Meta.DisplayName != "" {
		display = st.Meta.DisplayName
	}
	var size int64
	var newest time.Time
	for _, p := range old {
		size += stacks.DirSizeBytes(p)
		if t := stacks.DirModTime(p); t.After(newest) {
			newest = t
		}
	}
	var cp struct {
		ok bool
		c  backup.KeptCopy
	}
	if r.backupMgr != nil {
		cp.c, cp.ok = r.backupMgr.KeptBestCopy(req.Context(), name, hdd)
	}
	lang := r.langFor(req)
	data := keptChoiceData{
		Code:       "kept_data_choice",
		Title:      r.msgLang(lang, "kept.choice.title"),
		Body:       r.msgLang(lang, "kept.choice.body", display, appbackup.HumanizeBytes(size), localDay(newest)),
		UseLabel:   r.msgLang(lang, "kept.choice.use.label"),
		UseOffered: cp.ok,
		FreshLabel: r.msgLang(lang, "kept.choice.fresh.label"),
		FreshDesc:  r.msgLang(lang, "kept.choice.fresh.desc"),
		NotBacked:  r.msgLang(lang, "kept.not_backed_up"),
	}
	if cp.ok {
		data.UseDesc = r.msgLang(lang, "kept.choice.use.desc_from", r.keptCopyName(lang, cp.c))
	} else {
		data.UseOff = r.msgLang(lang, "kept.choice.use_off")
	}

	switch choice {
	case "":
		r.logger.Printf("[INFO] [api] Deploy %s: the drive already holds its old data %v (%d bytes) — asking the household (use offered: %v)", name, old, size, cp.ok)
		writeJSON(w, http.StatusConflict, apiResponse{OK: false, Error: data.Title, Data: data})
		return true
	case stacks.KeptChoiceUse:
		if !cp.ok {
			r.logger.Printf("[WARN] [api] Deploy %s: use my kept data REFUSED — no database copy for %s", name, hdd)
			writeJSON(w, http.StatusConflict, apiResponse{OK: false, Error: data.UseOff, Data: data})
			return true
		}
		if st := r.backupMgr.RestoreStatus(); st.Running || r.backupMgr.IsRunning() {
			writeJSON(w, http.StatusConflict, apiResponse{OK: false, Error: r.msgLang(lang, "api.kept.busy")})
			return true
		}
		src := cp.c.UnitDir
		if cp.c.Tier == backup.KeptTierOffsite {
			src = "off-site snapshot " + cp.c.SnapshotID
		}
		r.logger.Printf("[INFO] [api] Deploy %s: USE MY KEPT DATA — loading from %s (tier %d, %s) under the kept files %v", name, src, cp.c.Tier, cp.c.Time.UTC().Format(time.RFC3339), old)
		r.dropLeftoverHold(name, "use-kept-data") // R-704: this is a new install of an app that is not installed
		r.startKeptLoad(name, hdd, cp.c, lang, nil)
		writeJSON(w, http.StatusAccepted, apiResponse{OK: true, Message: r.msgLang(lang, "kept.load.started", display)})
		return true
	default:
		writeJSON(w, http.StatusBadRequest, apiResponse{OK: false, Error: fmt.Sprintf("kept_data %q is not a choice", choice)})
		return true
	}
}

// keptCopyName names a copy for the household: which copy and its date („saját mentés, 2026-09-28 04:15").
func (r *Router) keptCopyName(lang string, c backup.KeptCopy) string {
	return r.msgLang(lang, backup.KeptCopyKey(c.Tier), localMinute(c.Time))
}

// startKeptLoad runs the load and, when it succeeded, the app's after_load. then(ok) runs last. The
// off-site copy goes through LoadKeptOffsite (download the unit alone, judge it, then the same restore).
func (r *Router) startKeptLoad(name, drive string, c backup.KeptCopy, lang string, then func(ok bool)) {
	display := name
	if st, ok := r.stackMgr.GetStack(name); ok && st.Meta.DisplayName != "" {
		display = st.Meta.DisplayName
	}
	okMsg := func(error) string { return r.msgLang(lang, "kept.load.done", display) }
	failMsg := func(err error) string { return r.msgLang(lang, "kept.load.failed", display, err) }
	if c.Tier == backup.KeptTierOffsite {
		r.backupMgr.LoadKeptOffsite(name, drive, c, nil, okMsg, failMsg, r.keptAfterLoad(name, then))
		return
	}
	r.backupMgr.LoadKeptApp(name, c.UnitDir, okMsg, failMsg, r.keptAfterLoad(name, then))
}

// keptAfterLoad runs the app's after_load when the load succeeded, then then(ok).
func (r *Router) keptAfterLoad(name string, then func(ok bool)) func(ok bool) {
	return func(ok bool) {
		if ok {
			if ran, err := r.stackMgr.RunAfterLoad(name, 10*time.Minute); ran && err != nil {
				r.logger.Printf("[WARN] [api] kept load %s: after_load failed: %v", name, err)
			}
		}
		if then != nil {
			then(ok)
		}
	}
}

func localDay(t time.Time) string {
	if t.IsZero() {
		return "?"
	}
	return t.In(budapest()).Format("2006-01-02")
}

// localMinute is localDay with the time of day — the kept list's format, so both pages print one date.
func localMinute(t time.Time) string {
	if t.IsZero() {
		return "?"
	}
	return t.In(budapest()).Format("2006-01-02 15:04")
}

func budapest() *time.Location {
	loc, err := time.LoadLocation("Europe/Budapest")
	if err != nil {
		return time.UTC
	}
	return loc
}