package api

// The home-charger scheduler: the user's own list of charging tasks.
//
// The charger's own cloud schedule can say one thing — "charge between these
// hours" — and it says it inside one charger. This is a list, and each entry is
// a whole flow: start at 23:00, cap to 10 A at 01:00, stop at 06:30, on these
// chargers, on these days. One named thing, switched on and off as one.
//
//	GET    /api/charging-tasks                     — the caller's tasks, earliest first
//	POST   /api/charging-tasks                     — write one
//	PATCH  /api/charging-tasks/{id}                — edit one (any subset of its fields)
//	DELETE /api/charging-tasks/{id}                — forget one
//	POST   /api/charging-tasks/{id}/steps/{n}/run  — fire one step now
//
// A task belongs to the person, like the chargers it acts on, so there is no
// sharing here: everyone sees their own list only. Firing one is the business of
// chargingtasks_run.go, which is also what the ticker calls.

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"sort"
	"strconv"
	"strings"

	"drivervault/apiserver/internal/models"
)

// The actions a step may carry. Each is a control command the charger already
// understands; the scheduler adds no verbs of its own, so a task can only ask
// for something the buttons on the Charging page can ask for by hand.
var taskActions = map[string]bool{
	"start": true,
	"stop":  true,
	"limit": true,
	"boost": true,
}

// maxTaskSteps bounds one task's flow. Well past any real schedule — a night
// rate is two or three steps — and it keeps a client from parking an unbounded
// blob on the record, which the sweep then reads every thirty seconds.
const maxTaskSteps = 24

// chargingTaskRecord is the PocketBase-facing shape of a task.
type chargingTaskRecord struct {
	ID         string                `json:"id"`
	Name       string                `json:"name"`
	Chargers   []string              `json:"chargers"`
	Steps      []models.ChargingStep `json:"steps"`
	Zone       string                `json:"zone"`
	Days       []int                 `json:"days"`
	Enabled    bool                  `json:"enabled"`
	LastRun    string                `json:"last_run"`
	LastResult string                `json:"last_result"`
	Owner      string                `json:"owner"`
	Created    string                `json:"created"`
}

func (rec chargingTaskRecord) toModel() models.ChargingTask {
	// The lists are never null on the wire: the page iterates them, and a null
	// would make "every charger" and "every day" read as an error there.
	chargers := rec.Chargers
	if chargers == nil {
		chargers = []string{}
	}
	days := rec.Days
	if days == nil {
		days = []int{}
	}
	steps := rec.Steps
	if steps == nil {
		steps = []models.ChargingStep{}
	}
	return models.ChargingTask{
		ID:         rec.ID,
		Name:       rec.Name,
		Chargers:   chargers,
		Steps:      steps,
		Zone:       rec.Zone,
		Days:       days,
		Enabled:    rec.Enabled,
		LastRun:    rec.LastRun,
		LastResult: rec.LastResult,
		Created:    rec.Created,
	}
}

// firstStepTime is the time of day a task begins — its first step's, which is
// what the list is ordered by, so the evening's task sits below the morning's. A
// task with no steps cannot exist, but the ordering must not depend on that.
func (rec chargingTaskRecord) firstStepTime() string {
	if len(rec.Steps) == 0 {
		return "99:99"
	}
	return rec.Steps[0].Time
}

// chargingTaskBody is the write shape. Every field is a pointer so a PATCH can
// name one of them without the rest being read as "clear these" — a task
// switched off from the list must not lose its flow on the way.
type chargingTaskBody struct {
	Name     *string                `json:"name"`
	Chargers *[]string              `json:"chargers"`
	Steps    *[]models.ChargingStep `json:"steps"`
	Zone     *string                `json:"zone"`
	Days     *[]int                 `json:"days"`
	Enabled  *bool                  `json:"enabled"`
}

// parseHHMM splits a 24-hour clock time into its two numbers. "H:MM" is accepted
// as well as "HH:MM"; anything else is not a time of day.
func parseHHMM(raw string) (int, int, bool) {
	hh, mm, found := strings.Cut(strings.TrimSpace(raw), ":")
	if !found || len(hh) == 0 || len(hh) > 2 || len(mm) != 2 {
		return 0, 0, false
	}
	h, err := strconv.Atoi(hh)
	if err != nil {
		return 0, 0, false
	}
	m, err := strconv.Atoi(mm)
	if err != nil {
		return 0, 0, false
	}
	if h < 0 || h > 23 || m < 0 || m > 59 {
		return 0, 0, false
	}
	return h, m, true
}

// normalizeTaskTime returns the padded 24-hour form of a time of day, or "" for
// anything that is not one.
func normalizeTaskTime(raw string) string {
	h, m, ok := parseHHMM(raw)
	if !ok {
		return ""
	}
	return fmt.Sprintf("%02d:%02d", h, m)
}

// normalizeDays drops anything that is not a weekday number and sorts what is
// left, so the stored list reads the same however the client sent it. Empty
// stays empty, which means every day.
func normalizeDays(days []int) []int {
	seen := [7]bool{}
	for _, d := range days {
		if d >= 0 && d <= 6 {
			seen[d] = true
		}
	}
	out := []int{}
	for d, ok := range seen {
		if ok {
			out = append(out, d)
		}
	}
	return out
}

// normalizeSteps validates a flow, keeping the steps in the order they were
// written.
//
// Not sorted by time: a night crosses midnight, and clock order would file
// "start at 23:00" last, behind the stop that closes it. Nothing about firing
// depends on the order — every step is timed on its own — so the order is free
// to be the one that reads as the intention it is.
func normalizeSteps(steps []models.ChargingStep) ([]models.ChargingStep, error) {
	if len(steps) == 0 {
		return nil, fmt.Errorf("a task needs at least one step")
	}
	if len(steps) > maxTaskSteps {
		return nil, fmt.Errorf("a task can hold at most %d steps", maxTaskSteps)
	}
	out := make([]models.ChargingStep, 0, len(steps))
	for i, step := range steps {
		action := strings.TrimSpace(step.Action)
		if !taskActions[action] {
			return nil, fmt.Errorf("step %d: unknown action: %s", i+1, action)
		}
		at := normalizeTaskTime(step.Time)
		if at == "" {
			return nil, fmt.Errorf("step %d: time must be a 24-hour clock time, e.g. 23:00", i+1)
		}
		// The ceiling only means anything to "limit", but it is kept whatever the
		// action is: switching a step to "limit" and back should not lose the amps
		// that were typed. 6 A is the charger's own floor — below it the box pauses
		// rather than charging slowly — and its ratings top out at 32 A.
		if step.Amps != 0 && (step.Amps < 6 || step.Amps > 32) {
			return nil, fmt.Errorf("step %d: the current limit must be between 6 and 32 A", i+1)
		}
		// A limit step with no ceiling would fire and ask the charger for 0 A.
		if action == "limit" && step.Amps <= 0 {
			return nil, fmt.Errorf("step %d: a limit step needs the amps to limit to", i+1)
		}
		out = append(out, models.ChargingStep{Action: action, Amps: step.Amps, Time: at})
	}
	return out, nil
}

// taskPayload turns a write body into the PocketBase fields it names, validating
// as it goes. `full` demands the fields a task cannot exist without, so a POST is
// checked as a whole and a PATCH only where it speaks.
func taskPayload(body chargingTaskBody, full bool) (map[string]any, error) {
	payload := map[string]any{}

	if body.Name != nil {
		name := strings.TrimSpace(*body.Name)
		if name == "" {
			return nil, fmt.Errorf("name is required")
		}
		payload["name"] = name
	} else if full {
		return nil, fmt.Errorf("name is required")
	}

	if body.Steps != nil {
		steps, err := normalizeSteps(*body.Steps)
		if err != nil {
			return nil, err
		}
		payload["steps"] = steps
	} else if full {
		return nil, fmt.Errorf("a task needs at least one step")
	}

	if body.Chargers != nil {
		ids := []string{}
		for _, id := range *body.Chargers {
			if id = strings.TrimSpace(id); id != "" {
				ids = append(ids, id)
			}
		}
		payload["chargers"] = ids
	}
	if body.Days != nil {
		payload["days"] = normalizeDays(*body.Days)
	}
	if body.Zone != nil {
		payload["zone"] = strings.TrimSpace(*body.Zone)
	}
	if body.Enabled != nil {
		payload["enabled"] = *body.Enabled
	} else if full {
		// A task written without saying otherwise is on: nobody fills in a
		// schedule in order to leave it switched off.
		payload["enabled"] = true
	}
	return payload, nil
}

// listChargingTasks returns the caller's own tasks, the one that starts earliest
// first — the order the day runs them in, which is the order a schedule is read
// in. Ordered here rather than by PocketBase because the time a task starts is
// now inside its flow, which is not a column to sort on.
func (s *Server) listChargingTasks(w http.ResponseWriter, r *http.Request) {
	me := s.currentUserID(r)
	if me == "" {
		writeError(w, http.StatusUnauthorized, "not authenticated")
		return
	}
	res, err := s.pb.List(r.Context(), colChargingTasks, url.Values{
		"filter":  {fmt.Sprintf("owner='%s'", me)},
		"perPage": {"200"},
	})
	if err != nil {
		writePBError(w, err)
		return
	}
	var recs []chargingTaskRecord
	if err := json.Unmarshal(res.Items, &recs); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	sort.SliceStable(recs, func(i, j int) bool {
		return recs[i].firstStepTime() < recs[j].firstStepTime()
	})
	out := make([]models.ChargingTask, 0, len(recs))
	for _, rec := range recs {
		out = append(out, rec.toModel())
	}
	writeJSON(w, http.StatusOK, map[string]any{"tasks": out})
}

// ownedChargingTask fetches one task and checks it is the caller's. It writes the
// error response itself and returns ok=false when it is not.
func (s *Server) ownedChargingTask(w http.ResponseWriter, r *http.Request) (chargingTaskRecord, bool) {
	var rec chargingTaskRecord
	id := strings.TrimSpace(r.PathValue("id"))
	if id == "" {
		writeError(w, http.StatusBadRequest, "task id is required")
		return rec, false
	}
	if err := s.pb.GetOne(r.Context(), colChargingTasks, id, &rec); err != nil {
		writePBError(w, err)
		return rec, false
	}
	// Someone else's task is not found rather than forbidden, as a charger is:
	// whether a record exists is not this caller's business either.
	if rec.Owner != s.currentUserID(r) {
		writeError(w, http.StatusNotFound, "task not found")
		return rec, false
	}
	return rec, true
}

func (s *Server) createChargingTask(w http.ResponseWriter, r *http.Request) {
	me := s.currentUserID(r)
	if me == "" {
		writeError(w, http.StatusUnauthorized, "not authenticated")
		return
	}
	var body chargingTaskBody
	if err := decodeJSON(r, &body); err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	payload, err := taskPayload(body, true)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	payload["owner"] = me
	var rec chargingTaskRecord
	if err := s.pb.Create(r.Context(), colChargingTasks, payload, &rec); err != nil {
		writePBError(w, err)
		return
	}
	writeJSON(w, http.StatusCreated, map[string]any{"task": rec.toModel()})
}

func (s *Server) updateChargingTask(w http.ResponseWriter, r *http.Request) {
	rec, ok := s.ownedChargingTask(w, r)
	if !ok {
		return
	}
	var body chargingTaskBody
	if err := decodeJSON(r, &body); err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	payload, err := taskPayload(body, false)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	if len(payload) == 0 {
		writeJSON(w, http.StatusOK, map[string]any{"task": rec.toModel()})
		return
	}
	var updated chargingTaskRecord
	if err := s.pb.Update(r.Context(), colChargingTasks, rec.ID, payload, &updated); err != nil {
		writePBError(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"task": updated.toModel()})
}

func (s *Server) deleteChargingTask(w http.ResponseWriter, r *http.Request) {
	rec, ok := s.ownedChargingTask(w, r)
	if !ok {
		return
	}
	if err := s.pb.Delete(r.Context(), colChargingTasks, rec.ID); err != nil {
		writePBError(w, err)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// runChargingStepNow fires one step of a task on demand — the "Run now" beside
// it. One step rather than the whole flow, because a flow is not a thing that
// can happen at once: running a start and the stop that closes it back to back
// would leave the charger where it began and prove nothing.
//
// It takes the same path the ticker does, so what comes back is exactly what
// that step will do at its own time, errors included. A switched-off task still
// runs from here: the switch says whether the clock fires it, not whether the
// button does.
func (s *Server) runChargingStepNow(w http.ResponseWriter, r *http.Request) {
	rec, ok := s.ownedChargingTask(w, r)
	if !ok {
		return
	}
	n, err := strconv.Atoi(strings.TrimSpace(r.PathValue("step")))
	if err != nil || n < 0 || n >= len(rec.Steps) {
		writeError(w, http.StatusNotFound, "this task has no such step")
		return
	}
	who := caller(r)
	if who == nil {
		writeError(w, http.StatusUnauthorized, "not authenticated")
		return
	}
	step := rec.Steps[n]
	results := s.fireChargingSteps(r.Context(), who, rec, []models.ChargingStep{step})
	s.recordTaskRun(r.Context(), rec, step, results)
	// The same line that was just stored, so the row the caller updates from this
	// answer reads identically to the one a page reload would fetch.
	writeJSON(w, http.StatusOK, map[string]any{
		"results": results,
		"summary": taskRunLine(step, results),
	})
}