package main

import (
	"fmt"
	"net/http"
	"slices"
	"sort"
	"strconv"
	"strings"
	"time"

	"go.sour.is/xt/internal/otel"
	"go.sour.is/xt/internal/uuid"
	"go.yarn.social/lextwt"
)

type API struct {
	app      *appState
	db       db
	hostname string
}

func (a *API) plain(w http.ResponseWriter, r *http.Request) {
	reg := lextwt.NewTwtRegistry(mkPreambleDocs(a.hostname), nil)
	reg.WriteTo(w)
}

func (a *API) conv(w http.ResponseWriter, r *http.Request) {
	ctx, span := otel.Span(r.Context())
	defer span.End()

	w.Header().Set("Content-Type", "text/plain; charset=utf-8")

	hash := r.PathValue("hash")
	// if (len(hash) < 6 || len(hash) > 8) && !notAny(hash, "abcdefghijklmnopqrstuvwxyz234567") {
	// 	w.WriteHeader(http.StatusBadRequest)
	// 	return
	// }

	limit := 100
	if v, ok := strconv.Atoi(r.URL.Query().Get("limit")); ok == nil {
		limit = v
	}

	var offset int64 = 0
	if v, ok := strconv.ParseInt(r.URL.Query().Get("offset"), 10, 64); ok == nil {
		offset = v
	}

	twts, offset, end, err := fetchConv(ctx, a.db, hash, limit, offset)
	span.RecordError(err)
	if err != nil {
		http.Error(w, "ERR", 500)
		return
	}

	preamble := mkPreamble(a.hostname, "", "/api/plain/conv/"+hash, limit, int64(len(twts)), offset, end)
	reg := lextwt.NewTwtRegistry(preamble, twts)
	reg.WriteTo(w)
}

func (a *API) mentions(w http.ResponseWriter, r *http.Request) {
	ctx, span := otel.Span(r.Context())
	defer span.End()

	w.Header().Set("Content-Type", "text/plain; charset=utf-8")

	uri := r.URL.Query().Get("uri")
	if uri == "" {
		reg := lextwt.NewTwtRegistry(mkPreambleDocs(a.hostname), nil)
		reg.WriteTo(w)

		return
	}
	mention := uuid.UrlNS.UUID5(uri)

	limit := 100
	if v, ok := strconv.Atoi(r.URL.Query().Get("limit")); ok == nil {
		limit = v
	}

	var offset int64 = 0
	if v, ok := strconv.ParseInt(r.URL.Query().Get("offset"), 10, 64); ok == nil {
		offset = v
	}

	twts, offset, end, err := fetchMentions(ctx, a.db, mention, limit, offset)
	span.RecordError(err)
	if err != nil {
		http.Error(w, "ERR", 500)
		return
	}

	preamble := mkPreamble(a.hostname, uri, "/api/plain/mentions", limit, int64(len(twts)), offset, end)
	reg := lextwt.NewTwtRegistry(preamble, twts)
	reg.WriteTo(w)
}

func (a *API) twt(w http.ResponseWriter, r *http.Request) {
	ctx, span := otel.Span(r.Context())
	defer span.End()

	w.Header().Set("Content-Type", "text/plain; charset=utf-8")

	uri := r.URL.Query().Get("uri")

	limit := 100
	if v, ok := strconv.Atoi(r.URL.Query().Get("limit")); ok == nil {
		limit = v
	}
	limit = min(100, max(1, limit))

	var offset int64 = 0
	if v, ok := strconv.ParseInt(r.URL.Query().Get("offset"), 10, 64); ok == nil {
		offset = v
	}

	twts, offset, end, err := fetchTwts(ctx, a.db, uri, limit, offset)
	span.RecordError(err)
	if err != nil {
		http.Error(w, "ERR", 500)
		return
	}

	preamble := mkPreamble(a.hostname, uri, "/api/plain/twt", limit, int64(len(twts)), offset, end)

	reg := lextwt.NewTwtRegistry(preamble, twts)
	reg.WriteTo(w)
}

func (a *API) users(w http.ResponseWriter, r *http.Request) {
	ctx, span := otel.Span(r.Context())
	defer span.End()

	w.Header().Set("Content-Type", "text/plain; charset=utf-8")

	uri := r.URL.Query().Get("uri")
	q := r.URL.Query().Get("q")

	twts, err := fetchUsers(ctx, a.db, uri, q)
	if err != nil {
		http.Error(w, "ERR", 500)
		return
	}

	reg := lextwt.NewTwtRegistry(mkPreambleDocs(a.hostname), twts)
	reg.WriteTo(w)
}

func (a *API) queue(w http.ResponseWriter, r *http.Request) {
	lis := slices.Collect(a.app.queue.Iter())
	sort.Slice(lis, func(i, j int) bool {
		return lis[i].NextScanOn.Time.Before(lis[j].LastScanOn.Time)
	})
	for _, feed := range lis {
		fmt.Fprintln(w, feed.State, feed.NextScanOn.Time.Format(time.RFC3339), feed.Nick, feed.URI)
	}
}

func notAny(s string, chars string) bool {
	for _, c := range s {
		if !strings.ContainsRune(chars, c) {
			return false
		}
	}
	return true
}

func mkqry(uri string, limit int, offset int64) string {
	qry := make([]string, 0, 3)

	if uri != "" {
		qry = append(qry, "uri="+uri)
	}

	if limit != 100 {
		qry = append(qry, fmt.Sprint("limit=", limit))
	}

	if offset != 0 {
		qry = append(qry, fmt.Sprint("offset=", offset))
	}

	if len(qry) == 0 {
		return ""
	}

	return "?" + strings.Join(qry, "&")
}

func add(preamble lextwt.Comments, text string, v ...any) lextwt.Comments {
	if len(v) > 0 {
		text = fmt.Sprintf(text, v...)
	}
	return append(preamble, lextwt.NewComment("# "+text))
}
func addKey(preamble lextwt.Comments, key, value string, v ...any) lextwt.Comments {
	if len(v) > 0 {
		value = fmt.Sprintf(value, v...)
	}
	comment := fmt.Sprintf("# %s = %s", key, value)
	return append(preamble, lextwt.NewCommentValue(comment, key, value))
}

func mkPreamble(hostname, uri, path string, limit int, length, offset, end int64) lextwt.Comments {
	preamble := addKey(mkPreambleDocs(hostname), "twt range", "1 %d", end)
	preamble = addKey(preamble, "self", "%s%s%s", hostname, path, mkqry(uri, limit, offset))
	if next := offset + length; next < end {
		preamble = addKey(preamble, "next", "%s%s%s", hostname, path, mkqry(uri, limit, next))
	}
	if prev := offset - int64(limit); prev > 0 {
		preamble = addKey(preamble, "prev", "%s%s%s", hostname, path, mkqry(uri, limit, prev))
	}
	return preamble
}

var mkPreambleDocs = func(hostname string) lextwt.Comments {
	c := add(nil, iAmTheWatcher)
	c = add(c, "")
	c = add(c, "Usage:")
	c = add(c, "    %s/api/plain/users              View list of users and latest twt date.", hostname)
	c = add(c, "    %s/api/plain/twt                View all twts.", hostname)
	c = add(c, "    %s/api/plain/mentions?uri=:uri  View all mentions for uri.", hostname)
	c = add(c, "    %s/api/plain/conv/:hash         View all twts for a conversation subject.", hostname)
	c = add(c, "")
	c = add(c, "Options:")
	c = add(c, "    uri     Filter to show a specific users twts.")
	c = add(c, "    offset  Start index for quey.")
	c = add(c, "    limit   Count of items to return (going back in time).")
	return add(c, "")
}