package glamour

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"os"

	"github.com/muesli/termenv"
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/extension"
	"github.com/yuin/goldmark/parser"
	"github.com/yuin/goldmark/renderer"
	"github.com/yuin/goldmark/util"

	"github.com/charmbracelet/glamour/ansi"
)

// A TermRendererOption sets an option on a TermRenderer.
type TermRendererOption func(*TermRenderer) error

// TermRenderer can be used to render markdown content, posing a depth of
// customization and styles to fit your needs.
type TermRenderer struct {
	md          goldmark.Markdown
	ansiOptions ansi.Options
	buf         bytes.Buffer
	renderBuf   bytes.Buffer
}

// Render initializes a new TermRenderer and renders a markdown with a specific
// style.
func Render(in string, stylePath string) (string, error) {
	b, err := RenderBytes([]byte(in), stylePath)
	return string(b), err
}

// RenderWithEnvironmentConfig initializes a new TermRenderer and renders a
// markdown with a specific style defined by the GLAMOUR_STYLE environment variable.
func RenderWithEnvironmentConfig(in string) (string, error) {
	b, err := RenderBytes([]byte(in), getEnvironmentStyle())
	return string(b), err
}

// RenderBytes initializes a new TermRenderer and renders a markdown with a
// specific style.
func RenderBytes(in []byte, stylePath string) ([]byte, error) {
	r, err := NewTermRenderer(
		WithStylePath(stylePath),
	)
	if err != nil {
		return nil, err
	}
	return r.RenderBytes(in)
}

// NewTermRenderer returns a new TermRenderer the given options.
func NewTermRenderer(options ...TermRendererOption) (*TermRenderer, error) {
	tr := &TermRenderer{
		md: goldmark.New(
			goldmark.WithExtensions(
				extension.GFM,
				extension.DefinitionList,
			),
			goldmark.WithParserOptions(
				parser.WithAutoHeadingID(),
			),
		),
		ansiOptions: ansi.Options{
			WordWrap:     80,
			ColorProfile: termenv.TrueColor,
		},
	}
	for _, o := range options {
		if err := o(tr); err != nil {
			return nil, err
		}
	}
	ar := ansi.NewRenderer(tr.ansiOptions)
	tr.md.SetRenderer(
		renderer.NewRenderer(
			renderer.WithNodeRenderers(
				util.Prioritized(ar, 1000),
			),
		),
	)
	return tr, nil
}

// WithBaseURL sets a TermRenderer's base URL.
func WithBaseURL(baseURL string) TermRendererOption {
	return func(tr *TermRenderer) error {
		tr.ansiOptions.BaseURL = baseURL
		return nil
	}
}

// WithColorProfile sets the TermRenderer's color profile
// (TrueColor / ANSI256 / ANSI).
func WithColorProfile(profile termenv.Profile) TermRendererOption {
	return func(tr *TermRenderer) error {
		tr.ansiOptions.ColorProfile = profile
		return nil
	}
}

// WithStandardStyle sets a TermRenderer's styles with a standard (builtin)
// style.
func WithStandardStyle(style string) TermRendererOption {
	return func(tr *TermRenderer) error {
		styles, err := getDefaultStyle(style)
		if err != nil {
			return err
		}
		tr.ansiOptions.Styles = *styles
		return nil
	}
}

// WithAutoStyle sets a TermRenderer's styles with either the standard dark
// or light style, depending on the terminal's background color at run-time.
func WithAutoStyle() TermRendererOption {
	return WithStandardStyle("auto")
}

// WithEnvironmentConfig sets a TermRenderer's styles based on the
// GLAMOUR_STYLE environment variable.
func WithEnvironmentConfig() TermRendererOption {
	return WithStylePath(getEnvironmentStyle())
}

// WithStylePath sets a TermRenderer's style from stylePath. stylePath is first
// interpreted as a filename. If no such file exists, it is re-interpreted as a
// standard style.
func WithStylePath(stylePath string) TermRendererOption {
	return func(tr *TermRenderer) error {
		jsonBytes, err := ioutil.ReadFile(stylePath)
		switch {
		case err == nil:
			return json.Unmarshal(jsonBytes, &tr.ansiOptions.Styles)
		case os.IsNotExist(err):
			styles, err := getDefaultStyle(stylePath)
			if err != nil {
				return err
			}
			tr.ansiOptions.Styles = *styles
			return nil
		default:
			return err
		}
	}
}

// WithStyles sets a TermRenderer's styles.
func WithStyles(styles ansi.StyleConfig) TermRendererOption {
	return func(tr *TermRenderer) error {
		tr.ansiOptions.Styles = styles
		return nil
	}
}

// WithStylesFromJSONBytes sets a TermRenderer's styles by parsing styles from
// jsonBytes.
func WithStylesFromJSONBytes(jsonBytes []byte) TermRendererOption {
	return func(tr *TermRenderer) error {
		return json.Unmarshal(jsonBytes, &tr.ansiOptions.Styles)
	}
}

// WithStylesFromJSONFile sets a TermRenderer's styles from a JSON file.
func WithStylesFromJSONFile(filename string) TermRendererOption {
	return func(tr *TermRenderer) error {
		jsonBytes, err := ioutil.ReadFile(filename)
		if err != nil {
			return err
		}
		return json.Unmarshal(jsonBytes, &tr.ansiOptions.Styles)
	}
}

// WithWordWrap sets a TermRenderer's word wrap.
func WithWordWrap(wordWrap int) TermRendererOption {
	return func(tr *TermRenderer) error {
		tr.ansiOptions.WordWrap = wordWrap
		return nil
	}
}

func (tr *TermRenderer) Read(b []byte) (int, error) {
	return tr.renderBuf.Read(b)
}

func (tr *TermRenderer) Write(b []byte) (int, error) {
	return tr.buf.Write(b)
}

// Close must be called after writing to TermRenderer. You can then retrieve
// the rendered markdown by calling Read.
func (tr *TermRenderer) Close() error {
	err := tr.md.Convert(tr.buf.Bytes(), &tr.renderBuf)
	if err != nil {
		return err
	}

	tr.buf.Reset()
	return nil
}

// Render returns the markdown rendered into a string.
func (tr *TermRenderer) Render(in string) (string, error) {
	b, err := tr.RenderBytes([]byte(in))
	return string(b), err
}

// RenderBytes returns the markdown rendered into a byte slice.
func (tr *TermRenderer) RenderBytes(in []byte) ([]byte, error) {
	var buf bytes.Buffer
	err := tr.md.Convert(in, &buf)
	return buf.Bytes(), err
}

func getEnvironmentStyle() string {
	glamourStyle := os.Getenv("GLAMOUR_STYLE")
	if len(glamourStyle) == 0 {
		glamourStyle = "auto"
	}

	return glamourStyle
}

func getDefaultStyle(style string) (*ansi.StyleConfig, error) {
	if style == "auto" {
		if termenv.HasDarkBackground() {
			return &DarkStyleConfig, nil
		}
		return &LightStyleConfig, nil
	}

	styles, ok := DefaultStyles[style]
	if !ok {
		return nil, fmt.Errorf("%s: style not found", style)
	}
	return styles, nil
}