package web

import (
	"bytes"
	"encoding/json"
	"net/url"
	"regexp"
	"strings"
	"text/template"
	"time"

	"github.com/google/uuid"
)

// Theme is the structured, form-editable look of a blog. Stored as jsonb.
type Theme struct {
	BgColor string `json:"bg_color"`
	BgImage string `json:"bg_image"` // image uuid or ""
	BgMode  string `json:"bg_mode"`  // cover | tile | fixed

	ContentBg      string `json:"content_bg"`
	TextColor      string `json:"text_color"`
	LinkColor      string `json:"link_color"`
	LinkHover      string `json:"link_hover"`      // "" = same as LinkColor
	LinkUnderline  string `json:"link_underline"`  // always | hover | never
	ContentWidth   string `json:"content_width"`   // narrow | medium | wide
	ContentStyle   string `json:"content_style"`   // card | flat
	ContentPadding string `json:"content_padding"` // normal | compact | roomy
	Font           string `json:"font"`            // sans | serif | mono
	HeadingFont    string `json:"heading_font"`    // same | sans | serif | mono
	FontSize       string `json:"font_size"`       // small | normal | large

	HeaderShowTitle   bool   `json:"header_show_title"`
	HeaderImage       string `json:"header_image"`
	HeaderImageHeight string `json:"header_image_height"` // short | medium | tall
	HeaderAlign       string `json:"header_align"`        // left | center
	HeaderBg          string `json:"header_bg"`
	HeaderText        string `json:"header_text"`

	NavPosition     string `json:"nav_position"`      // below-header | top-bar | left-sidebar
	NavAlign        string `json:"nav_align"`         // left | center | right (horizontal menus)
	NavSidebarWidth string `json:"nav_sidebar_width"` // narrow | normal | wide (sidebar only)
	NavStyle        string `json:"nav_style"`         // normal | uppercase
	NavBg           string `json:"nav_bg"`
	NavText         string `json:"nav_text"`
	NavHover        string `json:"nav_hover"` // "" = same as NavText
	NavShowHome     bool   `json:"nav_show_home"`

	ShowDates  bool   `json:"show_dates"`
	DateFormat string `json:"date_format"` // long | short | iso

	FooterText    string `json:"footer_text"`
	FooterBg      string `json:"footer_bg"`
	FooterColor   string `json:"footer_color"`
	FooterShowRSS bool   `json:"footer_show_rss"`

	Favicon string `json:"favicon"` // image uuid or "" for the Blogspace default
}

func DefaultTheme() Theme {
	return Theme{
		BgColor: "#e9e6df", BgMode: "cover",
		ContentBg: "#ffffff", TextColor: "#222222", LinkColor: "#1a5fb4", LinkUnderline: "always",
		ContentWidth: "medium", ContentStyle: "card", ContentPadding: "normal",
		Font: "sans", HeadingFont: "same", FontSize: "normal",
		HeaderShowTitle: true, HeaderImageHeight: "medium", HeaderAlign: "left", HeaderBg: "#2f3a4a", HeaderText: "#ffffff",
		NavPosition: "below-header", NavAlign: "left", NavSidebarWidth: "normal", NavStyle: "normal", NavBg: "#ffffff", NavText: "#222222", NavShowHome: true,
		ShowDates: true, DateFormat: "long",
		FooterText: "", FooterBg: "#2f3a4a", FooterColor: "#d0d5dc", FooterShowRSS: true,
	}
}

// ParseTheme decodes stored JSON on top of the defaults so new fields get sane values.
func ParseTheme(raw json.RawMessage) Theme {
	t := DefaultTheme()
	if len(raw) > 0 {
		_ = json.Unmarshal(raw, &t)
	}
	t.normalize()
	return t
}

var hexColor = regexp.MustCompile(`^#[0-9a-fA-F]{6}$`)

func pick(v string, allowed ...string) string {
	for _, a := range allowed {
		if v == a {
			return v
		}
	}
	return allowed[0]
}

func color(v, def string) string {
	v = strings.TrimSpace(v)
	if hexColor.MatchString(v) {
		return strings.ToLower(v)
	}
	return def
}

// optColor is for colours that may be unset ("" = inherit).
func optColor(v string) string { return color(v, "") }

func imageID(v string) string {
	if _, err := uuid.Parse(v); err != nil {
		return ""
	}
	return v
}

// normalize clamps every field to an allowed value so the CSS template can trust them.
func (t *Theme) normalize() {
	d := DefaultTheme()
	t.BgColor = color(t.BgColor, d.BgColor)
	t.BgImage = imageID(t.BgImage)
	t.BgMode = pick(t.BgMode, "cover", "tile", "fixed")
	t.ContentBg = color(t.ContentBg, d.ContentBg)
	t.TextColor = color(t.TextColor, d.TextColor)
	t.LinkColor = color(t.LinkColor, d.LinkColor)
	t.LinkHover = optColor(t.LinkHover)
	t.LinkUnderline = pick(t.LinkUnderline, "always", "hover", "never")
	t.ContentWidth = pick(t.ContentWidth, "medium", "narrow", "wide")
	t.ContentStyle = pick(t.ContentStyle, "card", "flat")
	t.ContentPadding = pick(t.ContentPadding, "normal", "compact", "roomy")
	t.Font = pick(t.Font, "sans", "serif", "mono")
	t.HeadingFont = pick(t.HeadingFont, "same", "sans", "serif", "mono")
	t.FontSize = pick(t.FontSize, "normal", "small", "large")
	t.HeaderImage = imageID(t.HeaderImage)
	t.HeaderImageHeight = pick(t.HeaderImageHeight, "medium", "short", "tall")
	t.HeaderAlign = pick(t.HeaderAlign, "left", "center")
	t.HeaderBg = color(t.HeaderBg, d.HeaderBg)
	t.HeaderText = color(t.HeaderText, d.HeaderText)
	t.NavPosition = pick(t.NavPosition, "below-header", "top-bar", "left-sidebar")
	t.NavAlign = pick(t.NavAlign, "left", "center", "right")
	t.NavSidebarWidth = pick(t.NavSidebarWidth, "normal", "narrow", "wide")
	t.NavStyle = pick(t.NavStyle, "normal", "uppercase")
	t.NavBg = color(t.NavBg, d.NavBg)
	t.NavText = color(t.NavText, d.NavText)
	t.NavHover = optColor(t.NavHover)
	t.DateFormat = pick(t.DateFormat, "long", "short", "iso")
	t.FooterBg = color(t.FooterBg, d.FooterBg)
	t.FooterColor = color(t.FooterColor, d.FooterColor)
	if len(t.FooterText) > 2000 {
		t.FooterText = t.FooterText[:2000]
	}
	t.Favicon = imageID(t.Favicon)
}

// ThemeFromForm reads the design form on top of the current theme.
func ThemeFromForm(cur Theme, f url.Values) Theme {
	t := cur
	get := func(k string) string { return strings.TrimSpace(f.Get(k)) }
	on := func(k string) bool { return f.Get(k) == "on" }
	// Hover colours only apply when their checkbox is ticked; otherwise "inherit".
	hover := func(k string) string {
		if on(k + "_custom") {
			return get(k)
		}
		return ""
	}
	t.BgColor = get("bg_color")
	t.BgMode = get("bg_mode")
	t.ContentBg = get("content_bg")
	t.TextColor = get("text_color")
	t.LinkColor = get("link_color")
	t.LinkHover = hover("link_hover")
	t.LinkUnderline = get("link_underline")
	t.ContentWidth = get("content_width")
	t.ContentStyle = get("content_style")
	t.ContentPadding = get("content_padding")
	t.Font = get("font")
	t.HeadingFont = get("heading_font")
	t.FontSize = get("font_size")
	t.HeaderShowTitle = on("header_show_title")
	t.HeaderImageHeight = get("header_image_height")
	t.HeaderAlign = get("header_align")
	t.HeaderBg = get("header_bg")
	t.HeaderText = get("header_text")
	t.NavPosition = get("nav_position")
	t.NavAlign = get("nav_align")
	t.NavSidebarWidth = get("nav_sidebar_width")
	t.NavStyle = get("nav_style")
	t.NavBg = get("nav_bg")
	t.NavText = get("nav_text")
	t.NavHover = hover("nav_hover")
	t.NavShowHome = on("nav_show_home")
	t.ShowDates = on("show_dates")
	t.DateFormat = get("date_format")
	t.FooterText = get("footer_text")
	t.FooterBg = get("footer_bg")
	t.FooterColor = get("footer_color")
	t.FooterShowRSS = on("footer_show_rss")
	t.BgImage = pickImage(t.BgImage, get("bg_image"))
	t.HeaderImage = pickImage(t.HeaderImage, get("header_image"))
	t.Favicon = pickImage(t.Favicon, get("favicon"))
	t.normalize()
	return t
}

// pickImage applies an imagepick radio: "none" clears, an id selects, and an
// empty value (no radio in the form) keeps what was there.
func pickImage(cur, v string) string {
	switch v {
	case "":
		return cur
	case "none":
		return ""
	}
	return v
}

func (t Theme) JSON() json.RawMessage {
	b, _ := json.Marshal(t)
	return b
}

// FormatDate renders post dates in the blogger's chosen style.
func (t Theme) FormatDate(at time.Time) string {
	switch t.DateFormat {
	case "short":
		return at.Format("2 Jan 2006")
	case "iso":
		return at.Format("2006-01-02")
	}
	return at.Format("2 January 2006")
}

// ---- presets ----------------------------------------------------------------

// Preset is a named colour scheme; applying one touches only colours.
type Preset struct {
	Key, Name                            string
	Bg, ContentBg, Text, Link            string
	HeaderBg, HeaderText, NavBg, NavText string
	FooterBg, FooterText                 string
}

var presets = []Preset{
	{Key: "paper", Name: "Paper", Bg: "#e9e6df", ContentBg: "#ffffff", Text: "#222222", Link: "#1a5fb4",
		HeaderBg: "#2f3a4a", HeaderText: "#ffffff", NavBg: "#ffffff", NavText: "#222222", FooterBg: "#2f3a4a", FooterText: "#d0d5dc"},
	{Key: "night", Name: "Night", Bg: "#15171c", ContentBg: "#1f2229", Text: "#e6e6e6", Link: "#8ab4f8",
		HeaderBg: "#0d0f13", HeaderText: "#f2f2f2", NavBg: "#1a1d23", NavText: "#dcdcdc", FooterBg: "#0d0f13", FooterText: "#9a9a9a"},
	{Key: "ocean", Name: "Ocean", Bg: "#dfeef4", ContentBg: "#ffffff", Text: "#1b2b34", Link: "#0e7490",
		HeaderBg: "#0f4c5c", HeaderText: "#e6f7fb", NavBg: "#e6f4f8", NavText: "#0f4c5c", FooterBg: "#0f4c5c", FooterText: "#bfe3ec"},
	{Key: "forest", Name: "Forest", Bg: "#e4e9df", ContentBg: "#fbfcf8", Text: "#1f2a1f", Link: "#2f6b3a",
		HeaderBg: "#243d2a", HeaderText: "#eef5ea", NavBg: "#eef3e8", NavText: "#243d2a", FooterBg: "#243d2a", FooterText: "#bccfb8"},
	{Key: "slate", Name: "Slate", Bg: "#f0f0f0", ContentBg: "#ffffff", Text: "#2a2a2a", Link: "#4a4a4a",
		HeaderBg: "#ffffff", HeaderText: "#111111", NavBg: "#f7f7f7", NavText: "#333333", FooterBg: "#e5e5e5", FooterText: "#555555"},
	{Key: "rose", Name: "Rose", Bg: "#f7e9e6", ContentBg: "#fffaf8", Text: "#3a2426", Link: "#b03a48",
		HeaderBg: "#7a2e3a", HeaderText: "#fdf1f2", NavBg: "#fbe4e4", NavText: "#7a2e3a", FooterBg: "#7a2e3a", FooterText: "#e9c3c8"},
}

func Presets() []Preset { return presets }

func PresetByKey(key string) (Preset, bool) {
	for _, p := range presets {
		if p.Key == key {
			return p, true
		}
	}
	return Preset{}, false
}

// WithPreset swaps in a scheme's colours and drops custom hover colours; images
// and layout choices are untouched.
func (t Theme) WithPreset(p Preset) Theme {
	t.BgColor, t.ContentBg, t.TextColor, t.LinkColor = p.Bg, p.ContentBg, p.Text, p.Link
	t.HeaderBg, t.HeaderText, t.NavBg, t.NavText = p.HeaderBg, p.HeaderText, p.NavBg, p.NavText
	t.FooterBg, t.FooterColor = p.FooterBg, p.FooterText
	t.LinkHover, t.NavHover = "", ""
	t.normalize()
	return t
}

// ---- css --------------------------------------------------------------------

func fontStack(name string) string {
	switch name {
	case "serif":
		return `Georgia, "Times New Roman", Times, serif`
	case "mono":
		return `"Courier New", Courier, monospace`
	}
	return `"Helvetica Neue", Helvetica, Arial, sans-serif`
}

// Helpers used by the CSS template.
func (t Theme) FontFamily() string { return fontStack(t.Font) }

func (t Theme) HeadingFontFamily() string { return fontStack(t.HeadingFont) }

func (t Theme) FontSizePx() string {
	switch t.FontSize {
	case "small":
		return "15px"
	case "large":
		return "19px"
	}
	return "17px"
}

func (t Theme) MaxWidth() string {
	switch t.ContentWidth {
	case "narrow":
		return "640px"
	case "wide":
		return "1100px"
	}
	return "840px"
}

// ContentPaddingCSS returns desktop and phone paddings; "normal" is left to blog.css.
func (t Theme) ContentPaddingCSS() (desktop, phone string) {
	switch t.ContentPadding {
	case "compact":
		return "1em 1.2em", "0.7em"
	case "roomy":
		return "2.2em 3em", "1.4em"
	}
	return "", ""
}

func (t Theme) PaddingDesktop() string { d, _ := t.ContentPaddingCSS(); return d }
func (t Theme) PaddingPhone() string   { _, p := t.ContentPaddingCSS(); return p }

// SidebarWidthPx is the sidebar width when it differs from blog.css's 180px, else "".
func (t Theme) SidebarWidthPx() string {
	if t.NavPosition != "left-sidebar" {
		return ""
	}
	switch t.NavSidebarWidth {
	case "narrow":
		return "140px"
	case "wide":
		return "240px"
	}
	return ""
}

// SidebarContentMargin leaves the same 20px gutter blog.css uses.
func (t Theme) SidebarContentMargin() string {
	switch t.NavSidebarWidth {
	case "narrow":
		return "160px"
	case "wide":
		return "260px"
	}
	return ""
}

func (t Theme) HeaderImageMaxHeight() string {
	switch t.HeaderImageHeight {
	case "short":
		return "180px"
	case "tall":
		return "520px"
	}
	return "320px"
}

var themeCSS = template.Must(template.New("theme").Parse(`
body { margin:0; background-color:{{.BgColor}}; color:{{.TextColor}}; font-family:{{.FontFamily}}; font-size:{{.FontSizePx}}; line-height:1.55;
{{- if .BgImage}} background-image:url(/media/{{.BgImage}});
  {{- if eq .BgMode "cover"}} background-size:cover; background-position:center top; background-repeat:no-repeat;
  {{- else if eq .BgMode "fixed"}} background-size:cover; background-position:center; background-attachment:fixed; background-repeat:no-repeat;
  {{- else}} background-repeat:repeat;{{end}}
{{- end}} }
{{- if ne .HeadingFont "same"}}
h1, h2, h3, h4, h5, h6 { font-family:{{.HeadingFontFamily}}; }
{{- end}}
a { color:{{.LinkColor}};{{if eq .LinkUnderline "always"}} text-decoration:underline;{{else}} text-decoration:none;{{end}} }
{{- if or .LinkHover (eq .LinkUnderline "hover")}}
a:hover {{"{"}}{{if .LinkHover}} color:{{.LinkHover}};{{end}}{{if eq .LinkUnderline "hover"}} text-decoration:underline;{{end}} }
{{- end}}
.wrap { max-width:{{.MaxWidth}}; margin:0 auto; }
.site-header { background:{{.HeaderBg}}; color:{{.HeaderText}}; text-align:{{.HeaderAlign}}; }
.site-header a { color:{{.HeaderText}}; }
.header-image img { max-height:{{.HeaderImageMaxHeight}}; }
.site-nav { background:{{.NavBg}}; }
.nav-inner { text-align:{{.NavAlign}}; }
.site-nav a { color:{{.NavText}};{{if eq .NavStyle "uppercase"}} text-transform:uppercase; letter-spacing:0.05em; font-size:0.9em;{{end}} }
{{- if .NavHover}}
.site-nav a:hover { color:{{.NavHover}}; }
{{- end}}
{{- with .SidebarWidthPx}}
.nav-left-sidebar .body-wrap .site-nav, .nav-left-sidebar .body-wrap .sidebar-notices { width:{{.}}; }
.nav-left-sidebar .body-wrap .content { margin-left:{{$.SidebarContentMargin}}; }
@media (max-width: 700px) { .nav-left-sidebar .body-wrap .site-nav, .nav-left-sidebar .body-wrap .sidebar-notices { width:auto; } .nav-left-sidebar .body-wrap .content { margin-left:0; } }
{{- end}}
.content { background:{{.ContentBg}};{{with .PaddingDesktop}} padding:{{.}};{{end}}{{if eq .ContentStyle "flat"}} border-radius:0; box-shadow:none;{{end}} }
{{- with .PaddingPhone}}
@media (max-width: 700px) { .content { padding:{{.}}; } }
{{- end}}
.site-footer { background:{{.FooterBg}}; color:{{.FooterColor}}; }
.site-footer a { color:{{.FooterColor}}; }
`))

// CSS renders the per-blog stylesheet; all values were normalized so it is safe to inline.
func (t Theme) CSS() string {
	var b bytes.Buffer
	_ = themeCSS.Execute(&b, t)
	return b.String()
}