package gotext

import (
	"fmt"
	"io/ioutil"
	"os"
	"strconv"
	"strings"
	"sync"
)

type translation struct {
	id       string
	pluralId string
	trs      map[int]string
}

func newTranslation() *translation {
	tr := new(translation)
	tr.trs = make(map[int]string)

	return tr
}

func (t *translation) get() string {
	// Look for translation index 0
	if _, ok := t.trs[0]; ok {
		return t.trs[0]
	}

	// Return unstranlated id by default
	return t.id
}

func (t *translation) getN(n int) string {
	// Look for translation index
	if _, ok := t.trs[n]; ok {
		return t.trs[n]
	}

	// Return unstranlated plural by default
	return t.pluralId
}

/*
Po parses the content of any PO file and provides all the translation functions needed.
It's the base object used by all packafe methods. 
And it's safe for concurrent use by multiple goroutines by using the sync package for write locking. 

Example:

    import "github.com/leonelquinteros/gotext"

    func main() {
        // Create po object
        po := new(gotext.Po)

        // Parse .po file
        po.ParseFile("/path/to/po/file/translations.po")

        // Get translation
        println(po.Get("Translate this"))
    }

*/
type Po struct {
	// Storage
	translations map[string]*translation

	// Sync Mutex
	sync.RWMutex
}

// ParseFile tries to read the file by its provided path (f) and parse its content as a .po file.
func (po *Po) ParseFile(f string) {
	// Check if file exists
	info, err := os.Stat(f)
	if err != nil {
		return
	}

	// Check that isn't a directory
	if info.IsDir() {
		return
	}

	// Parse file content
	data, err := ioutil.ReadFile(f)
	if err != nil {
		return
	}

	po.Parse(string(data))
}

// Parse loads the translations specified in the provided string (str)
func (po *Po) Parse(str string) {
	if po.translations == nil {
		po.Lock()
		po.translations = make(map[string]*translation)
		po.Unlock()
	}

	lines := strings.Split(str, "\n")

	tr := newTranslation()

	for _, l := range lines {
		// Trim spaces
		l = strings.TrimSpace(l)

		// Skip empty lines
		if l == "" {
			continue
		}

		// Skip invalid lines
		if !strings.HasPrefix(l, "msgid") && !strings.HasPrefix(l, "msgid_plural") && !strings.HasPrefix(l, "msgstr") {
			continue
		}

		// Buffer msgid and continue
		if strings.HasPrefix(l, "msgid") && !strings.HasPrefix(l, "msgid_plural") {
			// Save current translation buffer.
			po.Lock()
			po.translations[tr.id] = tr
			po.Unlock()

			// Flush buffer
			tr = newTranslation()

			// Set id
			tr.id, _ = strconv.Unquote(strings.TrimSpace(strings.TrimPrefix(l, "msgid")))

			// Loop
			continue
		}

		// Check for plural form
		if strings.HasPrefix(l, "msgid_plural") {
			tr.pluralId, _ = strconv.Unquote(strings.TrimSpace(strings.TrimPrefix(l, "msgid_plural")))

			// Loop
			continue
		}

		// Save translation
		if strings.HasPrefix(l, "msgstr") {
			l = strings.TrimSpace(strings.TrimPrefix(l, "msgstr"))

			// Check for indexed translation forms
			if strings.HasPrefix(l, "[") {
				in := strings.Index(l, "]")
				if in == -1 {
					// Skip wrong index formatting
					continue
				}

				// Parse index
				i, err := strconv.Atoi(l[1:in])
				if err != nil {
					// Skip wrong index formatting
					continue
				}

				// Parse translation string
				tr.trs[i], _ = strconv.Unquote(strings.TrimSpace(l[in+1:]))

				// Loop
				continue
			}

			// Save single translation form under 0 index
			tr.trs[0], _ = strconv.Unquote(l)
		}
	}

	// Save last translation buffer.
	if tr.id != "" {
		po.Lock()
		po.translations[tr.id] = tr
		po.Unlock()
	}
}

// Get retrieves the corresponding translation for the given string.
// Supports optional parameters (vars... interface{}) to be inserted on the formatted string using the fmt.Printf syntax.
func (po *Po) Get(str string, vars ...interface{}) string {
	if po.translations != nil {
		if _, ok := po.translations[str]; ok {
			return fmt.Sprintf(po.translations[str].get(), vars...)
		}
	}

	// Return the same we received by default
	return fmt.Sprintf(str, vars...)
}

// GetN retrieves the (N)th plural form translation for the given string.
// If n == 0, usually the singular form of the string is returned as defined in the PO file.
// Supports optional parameters (vars... interface{}) to be inserted on the formatted string using the fmt.Printf syntax.
func (po *Po) GetN(str, plural string, n int, vars ...interface{}) string {
	if po.translations != nil {
		if _, ok := po.translations[str]; ok {
			return fmt.Sprintf(po.translations[str].getN(n), vars...)
		}
	}

	// Return the plural string we received by default
	return fmt.Sprintf(plural, vars...)
}