// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
// SPDX-License-Identifier: Apache-2.0

package template // import "miniflux.app/v2/internal/template"

import (
	"errors"
	"fmt"
	"html/template"
	"math"
	"net/mail"
	"net/url"
	"slices"
	"strconv"
	"strings"
	"time"

	"miniflux.app/v2/internal/config"
	"miniflux.app/v2/internal/crypto"
	"miniflux.app/v2/internal/locale"
	"miniflux.app/v2/internal/mediaproxy"
	"miniflux.app/v2/internal/model"
	"miniflux.app/v2/internal/reader/sanitizer"
	"miniflux.app/v2/internal/timezone"
	"miniflux.app/v2/internal/ui/static"
	"miniflux.app/v2/internal/urllib"
)

type funcMap struct {
	basePath  string
	iconPaths map[string]string
}

// Map returns a map of template functions that are compiled during template parsing.
func (f *funcMap) Map() template.FuncMap {
	// Pre-compute every icon URL once, as iconPath is called a lot during pages rendering.
	f.iconPaths = make(map[string]string, len(static.BinaryBundles))
	for filename, bundle := range static.BinaryBundles {
		f.iconPaths[filename] = f.basePath + "/icon/" + bundle.Checksum + "/" + filename
	}
	return template.FuncMap{
		"contains":         strings.Contains,
		"csp":              csp,
		"startsWith":       strings.HasPrefix,
		"formatFileSize":   formatFileSize,
		"dict":             dict,
		"truncate":         truncate,
		"isEmail":          isEmail,
		"baseURL":          config.Opts.BaseURL,
		"apiEnabled":       config.Opts.HasAPI,
		"rootURL":          config.Opts.RootURL,
		"disableLocalAuth": config.Opts.DisableLocalAuth,
		"oidcProviderName": config.Opts.OAuth2OIDCProviderName,
		"hasOAuth2Provider": func(provider string) bool {
			return config.Opts.OAuth2Provider() == provider
		},
		"hasAuthProxy": func() bool {
			return config.Opts.AuthProxyHeader() != ""
		},
		"routePath": func(format string, args ...any) string {
			if len(args) > 0 {
				return f.basePath + fmt.Sprintf(format, args...)
			}
			return f.basePath + format
		},
		"untrustedURL": untrustedURL,
		"safeCSS": func(str string) template.CSS {
			return template.CSS(str)
		},
		"safeJS": func(str string) template.JS {
			return template.JS(str)
		},
		"safeHTML": func(str string) template.HTML {
			return template.HTML(str)
		},
		"proxyFilter": mediaproxy.RewriteDocumentWithRelativeProxyURL,
		"proxyURL": func(link string) string {
			mediaProxyMode := config.Opts.MediaProxyMode()

			if mediaProxyMode == "all" || (mediaProxyMode != "none" && !urllib.IsHTTPS(link)) {
				return mediaproxy.ProxifyRelativeURL(link)
			}

			return link
		},
		"mustBeProxyfied": func(mediaType string) bool {
			return slices.Contains(config.Opts.MediaProxyResourceTypes(), mediaType)
		},
		"domain": urllib.Domain,
		"replace": func(str, old, new string) string {
			return strings.Replace(str, old, new, 1)
		},
		"isodate": func(ts time.Time) string {
			return ts.Format("2006-01-02 15:04:05")
		},
		"theme_color": model.ThemeColor,
		"iconPath":    f.iconPath,
		"icon":        f.iconFunc(),
		"nonce": func() string {
			return crypto.GenerateRandomStringHex(16)
		},
		"deRef":     func(i *int) int { return *i },
		"duration":  duration,
		"urlEncode": url.PathEscape,
		"subtract": func(a, b int) int {
			return a - b
		},
		"queryString": func(params map[string]any) string {
			if len(params) == 0 {
				return ""
			}

			values := url.Values{}
			for key, value := range params {
				switch v := value.(type) {
				case string:
					if v != "" {
						values.Set(key, v)
					}
				case int:
					if v != 0 {
						values.Set(key, strconv.Itoa(v))
					}
				case int64:
					if v != 0 {
						values.Set(key, strconv.FormatInt(v, 10))
					}
				case bool:
					if v {
						values.Set(key, "1")
					}
				default:
					if value != nil {
						str := fmt.Sprint(value)
						if str != "" {
							values.Set(key, str)
						}
					}
				}
			}

			encoded := values.Encode()
			if encoded == "" {
				return ""
			}

			return "?" + encoded
		},

		// These functions are overridden at runtime after parsing.
		"elapsed": func(timezone string, t time.Time) string {
			return ""
		},
		"t": func(key any, args ...any) string {
			return ""
		},
		"plural": func(key string, n int, args ...any) string {
			return ""
		},
	}
}

func (f *funcMap) iconPath(filename string) string {
	return f.iconPaths[filename]
}

func (f *funcMap) iconFunc() func(string) template.HTML {
	// Concatenation is used instead of fmt.Sprintf,
	// as it's much faster, and this function is called
	// a bunch of times per feed item on the main page.
	prefix := `<svg class="icon" aria-hidden="true"><use href="` + f.iconPath("sprite.svg") + `#icon-`
	const suffix = `"/></svg>`
	return func(iconName string) template.HTML {
		return template.HTML(prefix + iconName + suffix)
	}
}

func csp(user *model.User, nonce string) string {
	policies := map[string]string{
		"default-src":               "'none'",
		"frame-src":                 "*",
		"img-src":                   "* data:",
		"manifest-src":              "'self'",
		"media-src":                 "*",
		"require-trusted-types-for": "'script'",
		"script-src":                "'nonce-" + nonce + "' 'strict-dynamic'",
		"style-src":                 "'nonce-" + nonce + "'",
		"trusted-types":             "html url",
		"connect-src":               "'self'",
	}

	if user != nil {
		if user.ExternalFontHosts != "" {
			policies["font-src"] = user.ExternalFontHosts
			if user.Stylesheet != "" {
				policies["style-src"] += " " + user.ExternalFontHosts
			}
		}
	}

	var policy strings.Builder
	policy.Grow(350)
	for key, value := range policies {
		policy.WriteString(key)
		policy.WriteString(" ")
		policy.WriteString(value)
		policy.WriteString("; ")
	}

	return `<meta http-equiv="Content-Security-Policy" content="` + policy.String() + `">`
}

func dict(values ...any) (map[string]any, error) {
	if len(values)%2 != 0 {
		return nil, errors.New("dict expects an even number of arguments")
	}
	dict := make(map[string]any, len(values)/2)
	for i := 0; i < len(values); i += 2 {
		key, ok := values[i].(string)
		if !ok {
			return nil, errors.New("dict keys must be strings")
		}
		dict[key] = values[i+1]
	}
	return dict, nil
}

func truncate(str string, max int) string {
	if max <= 0 {
		panic("truncate: max must be greater than zero")
	}

	// Template callers pass feed titles from remote content. Scanning and
	// allocating the entire untrusted input just to truncate it could create a
	// denial-of-service risk, so stop as soon as we reach the requested limit.
	runeCount := 0
	for i := range str {
		if runeCount == max {
			return str[:i] + "…"
		}
		runeCount++
	}

	return str
}

func isEmail(str string) bool {
	_, err := mail.ParseAddress(str)
	return err == nil
}

// untrustedURL validates a feed-supplied URL against the sanitizer's scheme
// allowlist before exposing it to html/template. Returns "#" for unsafe URLs
// (e.g. javascript:, data:) so anchors render as inert links.
//
// Go's built-in html/template URL filter only allows http(s), mailto, and
// relative URLs — too narrow for feeds which legitimately use schemes like
// magnet:, feed:, webcal:, and tel:.
func untrustedURL(rawURL string) template.URL {
	if !sanitizer.HasValidURIScheme(rawURL) {
		return template.URL("#")
	}
	return template.URL(rawURL)
}

// Returns the duration in human readable format (hours and minutes).
func duration(t time.Time) string {
	return durationImpl(t, time.Now())
}

// Accepts now argument for easy testing
func durationImpl(t time.Time, now time.Time) string {
	if t.IsZero() {
		return ""
	}

	if diff := t.Sub(now); diff >= 0 {
		// Round to nearest second to get e.g. "14m56s" rather than "14m56.245483933s"
		return diff.Round(time.Second).String()
	}
	return ""
}

func elapsedTime(printer *locale.Printer, tz string, t time.Time) string {
	if t.IsZero() {
		return printer.Print("time_elapsed.not_yet")
	}

	now := timezone.Now(tz)
	t = timezone.Convert(tz, t)
	if now.Before(t) {
		return printer.Print("time_elapsed.not_yet")
	}

	diff := now.Sub(t)
	// Duration in seconds
	s := diff.Seconds()
	// Duration in days
	d := int(s / 86400)
	switch {
	case s < 60:
		return printer.Print("time_elapsed.now")
	case s < 3600:
		minutes := int(diff.Minutes())
		return printer.Plural("time_elapsed.minutes", minutes, minutes)
	case s < 86400:
		hours := int(diff.Hours())
		return printer.Plural("time_elapsed.hours", hours, hours)
	case d == 1:
		return printer.Print("time_elapsed.yesterday")
	case d < 21:
		return printer.Plural("time_elapsed.days", d, d)
	case d < 31:
		weeks := int(math.Round(float64(d) / 7))
		return printer.Plural("time_elapsed.weeks", weeks, weeks)
	case d < 365:
		months := int(math.Round(float64(d) / 30))
		return printer.Plural("time_elapsed.months", months, months)
	default:
		years := int(math.Round(float64(d) / 365))
		return printer.Plural("time_elapsed.years", years, years)
	}
}

func formatFileSize(b int64) string {
	const unit = 1024
	if b < unit {
		return fmt.Sprintf("%d B", b)
	}
	base := math.Log(float64(b)) / math.Log(unit)
	number := math.Pow(unit, base-math.Floor(base))
	return fmt.Sprintf("%.1f %ciB", number, "KMGTPE"[int64(base)-1])
}
