// go-sh-manymanuals TODO
package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"

	"github.com/charmbracelet/bubbles/spinner"
	"github.com/charmbracelet/bubbles/textinput"
	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
	pdf "github.com/johbar/go-poppler"
	"github.com/rkoesters/xdg"
	"github.com/sahilm/fuzzy"
	"golang.org/x/term"
)

// filenameFilterMode searches by PDF file name.
const filenameFilterMode = "filename"

// contentFilterMode searches by PDF contents.
const contentFilterMode = "content"

// help is the command-line interface help output.
const help = `go-sh-manymanuals: TODO

TODO

Options:
	-h    output help
`

// minCharsUntilFilter is the minimum amount of characters that are
// required before the filtering logic commences actually filtering.
const minCharsUntilFilter = 2

// helpFlag is the help flag for the command-line interface.
var helpFlag bool

// handleCliFlags handles command-line flags.
func handleCliFlags() {
	flag.BoolVar(&helpFlag, "h", false, "output help")
	flag.Parse()
}

// readPDF reads the plain text contents of a PDF. This does not include the
// formatting. Only the content you see when you view it through a PDF reader.
// The library we're using makes use of the C bindings to the Poppler PDF
// library https://poppler.freedesktop.org which appears to offer a good mix of
// reliability and effectiveness.
func readPDF(name string) (string, error) {
	doc, err := pdf.Open(name)
	if err != nil {
		return "", err
	}
	defer doc.Close()

	var txt string
	for i := 0; i < doc.GetNPages(); i++ {
		txt += doc.GetPage(i).Text()
	}

	return txt, nil
}

// model offers the core of the state for the entire UI.
type model struct {
	input      textinput.Model // Fuzzy search interface
	filterMode string          // The filtering mode ("filename", "content")

	datasheets             []datasheet    // All datasheets under cwd
	datasheetNames         []string       // All datasheet names (caching)
	datasheetsStyle        lipgloss.Style // Style to use for listing datasheets
	filteredDatasheets     []string       // Filtered view on all datasheets
	loadDatasheetSpinner   spinner.Model  // Spinner to show while loading datasheets
	datasheetsLoaded       bool           // Whether or not the datasheets are loaded or not
	datasheetViewport      viewport.Model // Viewport for the PDF content
	datasheetViewportStyle lipgloss.Style // Style to show while showing datasheet viewport

	indexSpinner spinner.Model // Spinner to show that content indexes are being loaded
	querySpinner spinner.Model // Spinner to show that content is being queried
}

// datasheetFromName retrieves a datasheet via a name.
func (m model) datasheetFromName(name string) string {
	for _, d := range m.datasheets {
		if d.filename == name {
			return d.contents
		}
	}
	return ""
}

// toggleFilterMode toggles the filter mode.
func (m *model) toggleFilterMode() {
	if m.filterMode == filenameFilterMode {
		m.filterMode = contentFilterMode
	} else {
		m.filterMode = filenameFilterMode
	}
}

// datasheet represents a datasheet on disk.
type datasheet struct {
	filename string // The name of the file
	absPath  string // the absolute file path
	contents string // the contents of the PDF
}

// initialModel constucts an initial state for the UI.
func initialModel(width int, height int) model {
	input := textinput.New()
	input.Focus()

	datasheetViewport := viewport.New(width/2+20, height/2)
	datasheetViewportStyle := lipgloss.NewStyle().
		BorderStyle(lipgloss.NormalBorder()).
		BorderForeground(lipgloss.Color("63")).
		Padding(2)

	// NOTE: disable the default keymap, we don't want to be able to
	//       scroll on this viewport or control it in any view. it's
	//       read-only
	datasheetViewport.KeyMap = viewport.KeyMap{}

	loadDatasheetSpinner := spinner.New()
	loadDatasheetSpinner.Spinner = spinner.Dot
	loadDatasheetSpinner.Style = lipgloss.NewStyle().
		Foreground(lipgloss.Color("205"))

	datasheetsStyle := lipgloss.NewStyle().
		Width(width/2 - 30).
		Height(height/2 - 30).
		MarginRight(2).
		BorderStyle(lipgloss.NormalBorder()).
		BorderForeground(lipgloss.Color("63")).
		Padding(2)

	m := model{
		input:      input,
		filterMode: filenameFilterMode,

		datasheetsLoaded:       false,
		loadDatasheetSpinner:   loadDatasheetSpinner,
		datasheetViewport:      datasheetViewport,
		datasheetViewportStyle: datasheetViewportStyle,
		datasheetsStyle:        datasheetsStyle,
	}

	return m
}

// loadedDatasheetsMsg signals to the UI that the datasheets have been loaded.
type loadedDatasheetsMsg struct {
	datasheets     []datasheet
	datasheetNames []string
}

// loadDatasheets loads the datasheets from disk. The UI shows a spinner while
// this is happening so that nobody gets bored.
func loadDatasheets(m model) loadedDatasheetsMsg {
	var datasheets []datasheet
	var datasheetNames []string

	// TODO: have this gradually update the UI as files are walked/parsed instead
	//       of blocking until everything is done in one big go. the current loading
	//       spinner will be there for a while on actually many manuals
	// TODO: handle error in interface?
	_ = filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		name := info.Name()
		if strings.HasSuffix(name, "pdf") {
			// TODO: handle error in interface?
			// TODO: don't read them all up front while blocking?
			//       we could run this in a goroutine somewhere
			//       this currently slows down startup time
			contents, _ := readPDF(path)

			datasheet := datasheet{
				filename: name,
				absPath:  path,
				contents: contents,
			}

			datasheets = append(datasheets, datasheet)
			datasheetNames = append(datasheetNames, name)
		}

		return nil
	})

	return loadedDatasheetsMsg{
		datasheets:     datasheets,
		datasheetNames: datasheetNames,
	}
}

// Init initialises the program.
func (m model) Init() tea.Cmd {
	return tea.Batch(
		func() tea.Msg { return loadDatasheets(m) },
		textinput.Blink,
		m.loadDatasheetSpinner.Tick,
	)
}

// filterDatasheetContents filters datasheet by content from user input.
func filterDatasheetContents(m model) []string {
	// TODO: implement indexing work beforehand
	//       wait for datasheetsLoaded to go true
	//       then iterate m.datasheets and index them
	//
	//       for this function, wait until Enter is hit to fire the query,
	//       run the query, fire the spinner and block any other queries
	//       coming in. return the list hits that come back from the query
	return []string{}
}

// filterDatasheetNames filters datasheet names based on user input.
func filterDatasheetNames(m model) []string {
	search := m.input.Value()
	if !(len(search) >= minCharsUntilFilter) {
		return m.datasheetNames
	}

	var matchedDatasheets []string
	matches := fuzzy.Find(search, m.datasheetNames)
	for _, match := range matches {
		matchedDatasheets = append(matchedDatasheets, match.Str)
	}

	if len(matches) > 0 {
		return matchedDatasheets
	}

	return m.datasheetNames
}

// Update updates the program state.
func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	var (
		cmd  tea.Cmd
		cmds []tea.Cmd
	)

	m.input, cmd = m.input.Update(msg)
	cmds = append(cmds, cmd)

	m.datasheetViewport, cmd = m.datasheetViewport.Update(msg)
	cmds = append(cmds, cmd)

	m.loadDatasheetSpinner, cmd = m.loadDatasheetSpinner.Update(msg)
	cmds = append(cmds, cmd)

	if m.input.Focused() && m.datasheetsLoaded {
		if m.filterMode == filenameFilterMode {
			m.filteredDatasheets = filterDatasheetNames(m)
		} else {
			m.filteredDatasheets = filterDatasheetContents(m)
		}

		// TODO: implement cursor for scrolling up/down filtered
		//       results so we can view the PDF contents as desired
		//       it's currently just the last one (closest to input)
		lastDatasheet := m.filteredDatasheets[len(m.filteredDatasheets)-1]
		viewportText := m.datasheetFromName(lastDatasheet)
		m.datasheetViewport.SetContent(viewportText)
	}

	switch msg := msg.(type) {
	case loadedDatasheetsMsg:
		m.datasheets = msg.datasheets
		m.datasheetNames = msg.datasheetNames
		m.filteredDatasheets = msg.datasheetNames

		selectedDatasheet := msg.datasheets[len(msg.datasheets)-1]
		m.datasheetViewport.SetContent(selectedDatasheet.contents)

		m.datasheetsLoaded = true
	case tea.WindowSizeMsg:
		// TODO: handle terminal resizing
		//       resize listing / viewport
	case tea.KeyMsg:
		switch msg.String() {
		case "ctrl+c":
			return m, tea.Quit
		case "tab":
			m.toggleFilterMode()
		case "o":
			selectedDatasheet := m.datasheets[len(m.datasheets)-1]
			// TODO: handle error
			_ = xdg.Open(selectedDatasheet.absPath)
		}
	}

	return m, tea.Batch(cmds...)
}

// View outputs the program state for viewing.
func (m model) View() string {
	body := strings.Builder{}

	var sheets string
	if !m.datasheetsLoaded {
		sheets = fmt.Sprintf("%s gathering datasheets...", m.loadDatasheetSpinner.View())
	} else {
		// TODO: paginate / trim view to last 10 or something?
		sheets = strings.Join(m.filteredDatasheets, "\n")
	}

	// TODO: style further with lipgloss, e.g. borders, margins, etc.
	panes := lipgloss.JoinHorizontal(
		lipgloss.Left,
		m.datasheetsStyle.Render(sheets),
		m.datasheetViewportStyle.Render(m.datasheetViewport.View()),
	)

	body.WriteString(panes)

	body.WriteString("\n" + m.input.View())

	mode := "filter: "
	if m.filterMode == filenameFilterMode {
		mode += "filename"
	} else {
		// TODO make this mode actually work once we figure out bleve
		mode += "content (FIXME)"
	}
	body.WriteString("\n" + mode)

	help := "[ctrl-c]: quit | [tab]: filter mode | [o]: open"
	body.WriteString("\n" + help)

	return body.String()
}

// main is the command-line entrypoint.
func main() {
	handleCliFlags()

	if helpFlag {
		fmt.Printf(help)
		os.Exit(0)
	}

	f, err := tea.LogToFile("debug.log", "debug")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	width, height, err := term.GetSize(0)
	if err != nil {
		log.Fatal(err)
	}

	p := tea.NewProgram(
		initialModel(width, height),
		tea.WithAltScreen(),
		tea.WithMouseCellMotion(),
	)

	if err := p.Start(); err != nil {
		fmt.Printf("oops, something went wrong: %v", err)
		os.Exit(1)
	}
}