// go-sh-manymanuals TODO
package main

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

	"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/sahilm/fuzzy"
)

// 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

	datasheets         []datasheet // All datasheets under cwd
	datasheetNames     []string    // All datasheet names (caching)
	filteredDatasheets []string    // Filtered view on all datasheets

	datasheetViewport viewport.Model // Viewport for the PDF content

	filterMode string // The filtering mode ("filename", "content")
}

// 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() model {
	input := textinput.New()
	input.Focus()

	var datasheets []datasheet
	var datasheetNames []string

	// 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
	})

	// TODO: set width/heigh to match terminal
	viewp := viewport.New(60, 30)
	selectedDatasheet := datasheets[len(datasheets)-1].contents
	viewp.SetContent(selectedDatasheet)

	m := model{
		input:              input,
		datasheets:         datasheets,
		datasheetNames:     datasheetNames,
		filteredDatasheets: datasheetNames,
		datasheetViewport:  viewp,
		filterMode:         filenameFilterMode,
	}

	return m
}

// Init initialises the program.
func (m model) Init() tea.Cmd {
	return textinput.Blink
}

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

	if m.input.Focused() {
		var matchedDatasheets []string

		search := m.input.Value()
		if len(search) >= minCharsUntilFilter {
			matches := fuzzy.Find(search, m.datasheetNames)
			for _, match := range matches {
				matchedDatasheets = append(matchedDatasheets, match.Str)
			}

			if len(matches) > 0 {
				m.filteredDatasheets = matchedDatasheets
			} else {
				m.filteredDatasheets = m.datasheetNames
			}
		} else {
			m.filteredDatasheets = m.datasheetNames
		}

		// 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)
	}

	// TODO: handle terminal resizing
	switch msg := msg.(type) {
	case tea.KeyMsg:
		switch msg.String() {
		case "ctrl+c":
			return m, tea.Quit
		case "tab":
			m.toggleFilterMode()
		}
	}

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

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

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

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

	// 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, sheets, 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"
	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 {
		fmt.Println("fatal:", err)
		os.Exit(1)
	}
	defer f.Close()

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

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