package web

// What the operator does on the mail page (novox/hq ADR 0517 §1, §2, §4, §5; issue 1859): tick an item done,
// undo it, remind it tomorrow, choose a mode. Each is a post RequireFormToken has already let through (the
// session's own token, csrf.go), calling its one mail-reading verb for the signed-in operator; the page keeps
// no state of its own (ADR 0440 §4). Posted by the page's script (X-Requested-With: fetch), it answers JSON:
// done, where to go, or failed with the cause. Posted by a plain form, it goes back to the list, or shows the
// list again saying the act failed and why — never dropped silently.

import (
	"context"
	"encoding/json"
	"net/http"
	"net/url"
	"strconv"
	"time"
)

// byScript says whether the page's own script posted the form.
func byScript(r *http.Request) bool { return r.Header.Get("X-Requested-With") == "fetch" }

func answerJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

// actFailed says an act failed, with its cause: JSON to the script, the list page with the cause otherwise.
func (b *Bundle) actFailed(w http.ResponseWriter, r *http.Request, mode Mode, cause string) {
	if byScript(r) {
		answerJSON(w, http.StatusBadGateway, map[string]any{"failed": cause})
		return
	}
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()
	data := b.listDataQuiet(ctx, r, mode)
	data.Notice = cause
	renderNamed(w, http.StatusBadGateway, "list", data)
}

// actDone answers an act that succeeded: done to the script, or back to the page at back.
func actDone(w http.ResponseWriter, r *http.Request, back string) {
	if byScript(r) {
		answerJSON(w, http.StatusOK, map[string]any{"done": true})
		return
	}
	http.Redirect(w, r, back, http.StatusSeeOther)
}

// listAddress is the list page's own address for mode.
func listAddress(mode Mode) string { return "/?" + url.Values{"mode": {mode.Name}}.Encode() }

// itemHandler is POST /item (1859/AC5): act handle, unhandle or remind, on the item (a task, a promise, or
// the mail itself) of the mail entry id, in the mode the page is in.
func (b *Bundle) itemHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "post only", http.StatusMethodNotAllowed)
		return
	}
	mode := modeNamed(r.PostFormValue("mode"))
	id, err := strconv.Atoi(r.PostFormValue("id"))
	if err != nil || id <= 0 {
		http.Error(w, "an item needs its mail entry's id", http.StatusBadRequest)
		return
	}
	ask := map[string]func(context.Context, map[string]any) (json.RawMessage, error){
		"handle": b.mailHandleAsk, "unhandle": b.mailUnhandleAsk, "remind": b.mailRemindAsk,
	}[r.PostFormValue("act")]
	if ask == nil {
		http.Error(w, "the act is none of handle, unhandle, remind", http.StatusBadRequest)
		return
	}
	args := map[string]any{"id": float64(id), "mode": mode.Name}
	if item := r.PostFormValue("item"); item != "" {
		args["item"] = item
	}
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()
	if _, err := ask(ctx, args); err != nil {
		b.actFailed(w, r, mode, "That did not happen: "+err.Error())
		return
	}
	back := r.PostFormValue("back")
	if back == "" || back[0] != '/' || (len(back) > 1 && back[1] == '/') {
		back = listAddress(mode) // only an address of this page itself
	}
	actDone(w, r, back)
}

// modeHandler is POST /mode (1859/AC2, AC5): the mode chosen, recorded (ADR 0517 §4), then its list.
func (b *Bundle) modeHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "post only", http.StatusMethodNotAllowed)
		return
	}
	mode := modeNamed(r.PostFormValue("mode"))
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()
	if _, err := b.mailRecordAsk(ctx, map[string]any{"what": "mode", "mode": mode.Name}); err != nil {
		b.actFailed(w, r, mode, "The mode chosen could not be kept: "+err.Error())
		return
	}
	if byScript(r) {
		answerJSON(w, http.StatusOK, map[string]any{"done": true, "go": listAddress(mode)})
		return
	}
	http.Redirect(w, r, listAddress(mode), http.StatusSeeOther)
}