/* Copyright Azareal 2016 - 2019 */
package common

import (
	"bytes"
	"crypto/sha256"
	"database/sql"
	"encoding/base64"
	"encoding/hex"
	"errors"
	htmpl "html/template"
	"io"
	"io/ioutil"
	"log"
	"mime"
	"net/http"
	"os"
	"path/filepath"
	"reflect"
	"strconv"
	"strings"
	"text/template"

	p "git.tuxpa.in/a/gosora/common/phrases"
)

var ErrNoDefaultTheme = errors.New("The default theme isn't registered in the system")
var ErrBadDefaultTemplate = errors.New("The template you tried to load doesn't exist in the interpreted pool.")

type Theme struct {
    Path string // Redirect this file to another folder

    Name           string
    FriendlyName   string
    Version        string
    Creator        string
    FullImage      string
    MobileFriendly bool
    Disabled       bool
    HideFromThemes bool
    BgAvatars      bool // For profiles, at the moment
    GridLists      bool // User Manager
    ForkOf         string
    Tag            string
    URL            string
    Docks          []string // Allowed Values: leftSidebar, rightSidebar, footer
    DocksID        []int    // Integer versions of Docks to try to get a speed boost in BuildWidget()
    Settings       map[string]ThemeSetting
    IntTmplHandle  *htmpl.Template
    // TODO: Do we really need both OverridenTemplates AND OverridenMap?
    OverridenTemplates []string
    OverridenMap       map[string]bool
    Templates          []TemplateMapping
    TemplatesMap       map[string]string
    TmplPtr            map[string]interface{}
    Resources          []ThemeResource
    ResourceTemplates  *template.Template

    // Dock intercepters
    // TODO: Implement this
    MapTmplToDock map[string]ThemeMapTmplToDock // map[dockName]data
    RunOnDock     func(string) string           //(dock string) (sbody string)
    RunOnDockID   func(int) string              //(dock int) (sbody string)

    // This variable should only be set and unset by the system, not the theme meta file
    // TODO: Should we phase out Active and make the default theme store the primary source of truth?
    Active bool
}

type ThemeSetting struct {
    FriendlyName string
    Options      []string
}

type TemplateMapping struct {
    Name   string
    Source string
    //When string
}

const (
    ResTypeUnknown = iota
    ResTypeSheet
    ResTypeScript
)
const (
    LocUnknown = iota
    LocGlobal
    LocFront
    LocPanel
)

type ThemeResource struct {
    Name     string
    Type     int // 0 = unknown, 1 = sheet, 2 = script
    Location string
    LocID    int
    Loggedin bool // Only serve this resource to logged in users
    Async    bool
}

type ThemeMapTmplToDock struct {
    //Name string
    File string
}

// TODO: It might be unsafe to call the template parsing functions with fsnotify, do something more concurrent
func (t *Theme) LoadStaticFiles() error {
    t.ResourceTemplates = template.New("")
    fmap := make(map[string]interface{})
    fmap["lang"] = func(phraseNameInt, tmplInt interface{}) interface{} {
        phraseName, ok := phraseNameInt.(string)
        if !ok {
            panic("phraseNameInt is not a string")
        }
        tmpl, ok := tmplInt.(CSSData)
        if !ok {
            panic("tmplInt is not a CSSData")
        }
        phrase, ok := tmpl.Phrases[phraseName]
        if !ok {
            // TODO: XSS? Only server admins should have access to theme files anyway, but think about it
            return "{lang." + phraseName + "}"
        }
        return phrase
    }
    fmap["toArr"] = func(args ...interface{}) []interface{} {
        return args
    }
    fmap["concat"] = func(args ...interface{}) interface{} {
        var out string
        for _, arg := range args {
            out += arg.(string)
        }
        return out
    }
    t.ResourceTemplates.Funcs(fmap)
    // TODO: Minify these
    //template.Must(t.ResourceTemplates.ParseGlob("./themes/" + t.Name + "/public/*.css"))
    fnames, err := filepath.Glob("./themes/" + t.Name + "/public/*.css")
    if err != nil {
        return err
    }
    for _, fname := range fnames {
        b, err := ioutil.ReadFile(fname)
        if err != nil {
            return err
        }
        //b := []byte("trolololol")
        //b = bytes.ReplaceAll(b, []byte{10}, []byte(""))
        //b = bytes.Replace(b, []byte("\n\n"), []byte(""), -1)
        //b = bytes.Replace(b, []byte("}\n."), []byte("}."), -1)
        //b = bytes.Replace(b, []byte("}\n:"), []byte("}:"), -1)
        s := func() string {
            s := string(b)
            rep := func(from, to string) {
                s = strings.Replace(s, from, to, -1)
            }
            rep("\r", "")
            rep("}\n", "}")
            rep("\n{", "{")
            rep("\n", "")
            rep(`
`, "")
            rep(": {{", ":{{")
            rep("display: ", "display:")
            rep("float: ", "float:")
            rep("-left: ", "-left:")
            rep("-right: ", "-right:")
            rep("-top: ", "-top:")
            rep("-bottom: ", "-bottom:")
            rep("border: ", "border:")
            rep("radius: ", "radius:")
            rep("content: ", "content:")
            rep("width: ", "width:")
            rep("padding: ", "padding:")
            rep("-size: ", "-size:")
            return s
        }()
        name := filepath.Base(fname)
        t := t.ResourceTemplates
        var tmpl *template.Template
        /*if name == t.Name() {
            tmpl = t
        } else {*/
        tmpl = t.New(name)
        //}
        _, err = tmpl.Parse(s)
        if err != nil {
            return err
        }
    }

    // It should be safe for us to load the files for all the themes in memory, as-long as the admin hasn't setup a ridiculous number of themes
    return t.AddThemeStaticFiles()
}

func (t *Theme) AddThemeStaticFiles() error {
    phraseMap := p.GetTmplPhrases()
    // TODO: Use a function instead of a closure to make this more testable? What about a function call inside the closure to take the theme variable into account?
    return filepath.Walk("./themes/"+t.Name+"/public", func(path string, f os.FileInfo, err error) error {
        DebugLog("Attempting to add static file '" + path + "' for default theme '" + t.Name + "'")
        if err != nil {
            return err
        }
        if f.IsDir() {
            return nil
        }

        path = strings.Replace(path, "\\", "/", -1)
        data, err := ioutil.ReadFile(path)
        if err != nil {
            return err
        }

        ext := filepath.Ext(path)
        if ext == ".js" {
            data = bytes.Replace(data, []byte("\r"), []byte(""), -1)
        }
        if ext == ".css" && len(data) != 0 {
            var b bytes.Buffer
            pieces := strings.Split(path, "/")
            filename := pieces[len(pieces)-1]
            // TODO: Prepare resource templates for each loaded langpack?
            err = t.ResourceTemplates.ExecuteTemplate(&b, filename, CSSData{Phrases: phraseMap})
            if err != nil {
                log.Print("Failed in adding static file '" + path + "' for default theme '" + t.Name + "'")
                return err
            }
            data = b.Bytes()
            rep := func(from, to string) {
                data = bytes.Replace(data, []byte(from), []byte(to), -1)
            }
            rep("\t", "")
            //rep("\n\n", "")
            rep("\n", "")
            rep("\n", "")
            rep(`
`, "")
            rep("}\n.", "}.")
            rep("}\n:", "}:")
            rep(": #", ":#")
            rep(" {", "{")
            rep("{\n", "{")
            rep(",\n", ",")
            rep(";\n", ";")
            rep(";\n}", ";}")
            rep(": 0px;", ":0;")
            rep("; }", ";}")
            rep(", #", ",#")
        }

        path = strings.TrimPrefix(path, "themes/"+t.Name+"/public")

        brData, err := CompressBytesBrotli(data)
        if err != nil {
            return err
        }
        // Don't use Brotli if we get meagre gains from it as it takes longer to process the responses
        if len(brData) >= (len(data) + 130) {
            brData = nil
        } else {
            diff := len(data) - len(brData)
            if diff <= len(data)/100 {
                brData = nil
            }
        }

        gzipData, err := CompressBytesGzip(data)
        if err != nil {
            return err
        }
        // Don't use Gzip if we get meagre gains from it as it takes longer to process the responses
        if len(gzipData) >= (len(data) + 150) {
            gzipData = nil
        } else {
            diff := len(data) - len(gzipData)
            if diff <= len(data)/100 {
                gzipData = nil
            }
        }

        // Get a checksum for CSPs and cache busting
        hasher := sha256.New()
        hasher.Write(data)
        sum := hasher.Sum(nil)
        checksum := hex.EncodeToString(sum)
        integrity := base64.StdEncoding.EncodeToString(sum)

        StaticFiles.Set(StaticFiles.Prefix+t.Name+path, &SFile{data, gzipData, brData, checksum, integrity, StaticFiles.Prefix + t.Name + path + "?h=" + checksum, 0, int64(len(data)), strconv.Itoa(len(data)), int64(len(gzipData)), strconv.Itoa(len(gzipData)), int64(len(brData)), strconv.Itoa(len(brData)), mime.TypeByExtension(ext), f, f.ModTime().UTC().Format(http.TimeFormat)})

        DebugLog("Added the '/" + t.Name + path + "' static file for theme " + t.Name + ".")
        return nil
    })
}

func (t *Theme) MapTemplates() {
    if t.Templates != nil {
        for _, themeTmpl := range t.Templates {
            if themeTmpl.Name == "" {
                LogError(errors.New("Invalid destination template name"))
            }
            if themeTmpl.Source == "" {
                LogError(errors.New("Invalid source template name"))
            }

            // `go generate` is one possibility for letting plugins inject custom page structs, but it would simply add another step of compilation. It might be simpler than the current build process from the perspective of the administrator?

            destTmplPtr, ok := TmplPtrMap[themeTmpl.Name]
            if !ok {
                return
            }
            sourceTmplPtr, ok := TmplPtrMap[themeTmpl.Source]
            if !ok {
                LogError(errors.New("The source template doesn't exist!"))
            }

            dTmplPtr, ok := destTmplPtr.(*func(interface{}, io.Writer) error)
            if !ok {
                log.Print("themeTmpl.Name: ", themeTmpl.Name)
                log.Print("themeTmpl.Source: ", themeTmpl.Source)
                LogError(errors.New("Unknown destination template type!"))
                return
            }

            sTmplPtr, ok := sourceTmplPtr.(*func(interface{}, io.Writer) error)
            if !ok {
                LogError(errors.New("The source and destination templates are incompatible"))
                return
            }

            overridenTemplates[themeTmpl.Name] = true
            *dTmplPtr = *sTmplPtr
        }
    }
}

func (t *Theme) setActive(active bool) error {
    var sink bool
    err := themeStmts.isDefault.QueryRow(t.Name).Scan(&sink)
    if err != nil && err != sql.ErrNoRows {
        return err
    }

    hasTheme := err != sql.ErrNoRows
    if hasTheme {
        _, err = themeStmts.update.Exec(active, t.Name)
    } else {
        _, err = themeStmts.add.Exec(t.Name, active)
    }
    if err != nil {
        return err
    }

    // TODO: Think about what we want to do for multi-server configurations
    log.Printf("Setting theme '%s' as the default theme", t.Name)
    t.Active = active
    return nil
}

func UpdateDefaultTheme(t *Theme) error {
    ChangeDefaultThemeMutex.Lock()
    defer ChangeDefaultThemeMutex.Unlock()

    err := t.setActive(true)
    if err != nil {
        return err
    }

    defaultTheme := DefaultThemeBox.Load().(string)
    dtheme, ok := Themes[defaultTheme]
    if !ok {
        return ErrNoDefaultTheme
    }
    err = dtheme.setActive(false)
    if err != nil {
        return err
    }

    DefaultThemeBox.Store(t.Name)
    ResetTemplateOverrides()
    t.MapTemplates()

    return nil
}

func (t Theme) HasDock(name string) bool {
    for _, dock := range t.Docks {
        if dock == name {
            return true
        }
    }
    return false
}

func (t Theme) BuildDock(dock string) (sbody string) {
    runOnDock := t.RunOnDock
    if runOnDock != nil {
        return runOnDock(dock)
    }
    return ""
}

func (t Theme) HasDockByID(id int) bool {
    for _, dock := range t.DocksID {
        if dock == id {
            return true
        }
    }
    return false
}

func (t Theme) BuildDockByID(id int) (sbody string) {
    runOnDock := t.RunOnDockID
    if runOnDock != nil {
        return runOnDock(id)
    }
    return ""
}

type GzipResponseWriter struct {
    io.Writer
    http.ResponseWriter
}

func (w GzipResponseWriter) Write(b []byte) (int, error) {
    return w.Writer.Write(b)
}

// NEW method of doing theme templates to allow one user to have a different theme to another. Under construction.
// TODO: Generate the type switch instead of writing it by hand
// TODO: Cut the number of types in half
func (t *Theme) RunTmpl(template string, pi interface{}, w io.Writer) error {
    // Unpack this to avoid an indirect call
    if gzw, ok := w.(GzipResponseWriter); ok {
        w = gzw.Writer
        gzw.Header().Set("Content-Type", "text/html;charset=utf-8")
    }

    getTmpl := t.GetTmpl(template)
    switch tmplO := getTmpl.(type) {
    case *func(interface{}, io.Writer) error:
        var tmpl = *tmplO
        return tmpl(pi, w)
    case func(interface{}, io.Writer) error:
        return tmplO(pi, w)
    case nil, string:
        //fmt.Println("falling back to interpreted for " + template)
        mapping, ok := t.TemplatesMap[template]
        if !ok {
            mapping = template
        }
        if t.IntTmplHandle.Lookup(mapping+".html") == nil {
            return ErrBadDefaultTemplate
        }
        return t.IntTmplHandle.ExecuteTemplate(w, mapping+".html", pi)
    default:
        log.Print("theme ", t)
        log.Print("template ", template)
        log.Print("pi ", pi)
        log.Print("tmplO ", tmplO)
        log.Print("getTmpl ", getTmpl)

        valueOf := reflect.ValueOf(tmplO)
        log.Print("initial valueOf.Type()", valueOf.Type())
        for valueOf.Kind() == reflect.Interface || valueOf.Kind() == reflect.Ptr {
            valueOf = valueOf.Elem()
            log.Print("valueOf.Elem().Type() ", valueOf.Type())
        }
        log.Print("deferenced valueOf.Type() ", valueOf.Type())
        log.Print("valueOf.Kind() ", valueOf.Kind())

        return errors.New("Unknown template type")
    }
}

// GetTmpl attempts to get the template for a specific theme, otherwise it falls back on the default template pointer, which if absent will fallback onto the template interpreter
func (t *Theme) GetTmpl(template string) interface{} {
    // TODO: Figure out why we're getting a nil pointer here when transpiled templates are disabled, I would have assumed that we would just fall back to !ok on this
    // Might have something to do with it being the theme's TmplPtr map, investigate.
    tmpl, ok := t.TmplPtr[template]
    if ok {
        return tmpl
    }
    tmpl, ok = TmplPtrMap[template+"_"+t.Name]
    if ok {
        return tmpl
    }
    tmpl, ok = TmplPtrMap[template]
    if ok {
        return tmpl
    }
    return template
}