package gotext

import (
	"bufio"
	"fmt"
	"github.com/leonelquinteros/anko/vm"
	"io/ioutil"
	"net/textproto"
	"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 package methods.
And it's safe for concurrent use by multiple goroutines by using the sync package for 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 {
	// Headers
	RawHeaders string

	// Language header
	Language string

	// Plural-Forms header
	PluralForms string

	// Parsed Plural-Forms header values
	nplurals int
	plural   string

	// Storage
	translations map[string]*translation
	contexts     map[string]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) {
	// Lock while parsing
	po.Lock()
	defer po.Unlock()

	// Init storage
	if po.translations == nil {
		po.translations = make(map[string]*translation)
		po.contexts = make(map[string]map[string]*translation)
	}

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

	// Translation buffer
	tr := newTranslation()

	// Context buffer
	ctx := ""

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

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

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

		// Buffer context and continue
		if strings.HasPrefix(l, "msgctxt") {
			// Save current translation buffer.
			// No context
			if ctx == "" {
				po.translations[tr.id] = tr
			} else {
				// Save context
				if _, ok := po.contexts[ctx]; !ok {
					po.contexts[ctx] = make(map[string]*translation)
				}
				po.contexts[ctx][tr.id] = tr
			}

			// Flush buffer
			tr = newTranslation()
			ctx = ""

			// Buffer context
			ctx, _ = strconv.Unquote(strings.TrimSpace(strings.TrimPrefix(l, "msgctxt")))

			// Loop
			continue
		}

		// Buffer msgid and continue
		if strings.HasPrefix(l, "msgid") && !strings.HasPrefix(l, "msgid_plural") {
			// Save current translation buffer if not inside a context.
			if ctx == "" {
				po.translations[tr.id] = tr

				// Flush buffer
				tr = newTranslation()
				ctx = ""
			} else if ctx != "" && tr.id != "" {
				// Save current translation buffer inside a context
				if _, ok := po.contexts[ctx]; !ok {
					po.contexts[ctx] = make(map[string]*translation)
				}
				po.contexts[ctx][tr.id] = tr

				// Flush buffer
				tr = newTranslation()
				ctx = ""
			}

			// 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, "[") {
				idx := strings.Index(l, "]")
				if idx == -1 {
					// Skip wrong index formatting
					continue
				}

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

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

				// Loop
				continue
			}

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

			// Loop
			continue
		}

		// Multi line strings and headers
		if strings.HasPrefix(l, "\"") && strings.HasSuffix(l, "\"") {
			// Check for multiline from previously set msgid
			if tr.id != "" {
				// Append to last translation found
				uq, _ := strconv.Unquote(l)
				tr.trs[len(tr.trs)-1] += uq

				// Loop
				continue
			}

			// Otherwise is a header
			h, err := strconv.Unquote(strings.TrimSpace(l))
			if err != nil {
				continue
			}

			po.RawHeaders += h
			continue
		}
	}

	// Save last translation buffer.
	if tr.id != "" {
		if ctx == "" {
			po.translations[tr.id] = tr
		} else {
			// Save context
			if _, ok := po.contexts[ctx]; !ok {
				po.contexts[ctx] = make(map[string]*translation)
			}
			po.contexts[ctx][tr.id] = tr
		}
	}

	// Parse headers
	po.RawHeaders += "\n\n"

	reader := bufio.NewReader(strings.NewReader(po.RawHeaders))
	tp := textproto.NewReader(reader)

	mimeHeader, err := tp.ReadMIMEHeader()
	if err != nil {
		return
	}

	// Get/save needed headers
	po.Language = mimeHeader.Get("Language")
	po.PluralForms = mimeHeader.Get("Plural-Forms")

	// Parse Plural-Forms formula
	if po.PluralForms == "" {
		return
	}

	// Split plural form header value
	pfs := strings.Split(po.PluralForms, ";")

	// Parse values
	for _, i := range pfs {
		vs := strings.SplitN(i, "=", 2)
		if len(vs) != 2 {
			continue
		}

		switch strings.TrimSpace(vs[0]) {
		case "nplurals":
			po.nplurals, _ = strconv.Atoi(vs[1])

		case "plural":
			po.plural = vs[1]
		}
	}
}

// pluralForm calculates the plural form index corresponding to n.
// Returns 0 on error
func (po *Po) pluralForm(n int) int {
	po.RLock()
	defer po.RUnlock()

	// Failsafe
	if po.nplurals < 1 {
		return 0
	}
	if po.plural == "" {
		return 0
	}

	// Init compiler
	env := vm.NewEnv()
	env.Define("n", n)

	plural, err := env.Execute(po.plural)
	if err != nil {
		return 0
	}
	if plural.Type().Name() == "bool" {
		if plural.Bool() {
			return 1
		} else {
			return 0
		}
	}

	if int(plural.Int()) > po.nplurals {
		return 0
	}

	return int(plural.Int())
}

// 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 {
	// Sync read
	po.RLock()
	defer po.RUnlock()

	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 of 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) GetN(str, plural string, n int, vars ...interface{}) string {
	// Sync read
	po.RLock()
	defer po.RUnlock()

	if po.translations != nil {
		if _, ok := po.translations[str]; ok {
			return fmt.Sprintf(po.translations[str].getN(po.pluralForm(n)), vars...)
		}
	}

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

// GetC retrieves the corresponding translation for a given string in the given context.
// Supports optional parameters (vars... interface{}) to be inserted on the formatted string using the fmt.Printf syntax.
func (po *Po) GetC(str, ctx string, vars ...interface{}) string {
	// Sync read
	po.RLock()
	defer po.RUnlock()

	if po.contexts != nil {
		if _, ok := po.contexts[ctx]; ok {
			if po.contexts[ctx] != nil {
				if _, ok := po.contexts[ctx][str]; ok {
					return fmt.Sprintf(po.contexts[ctx][str].get(), vars...)
				}
			}
		}
	}

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

// GetNC retrieves the (N)th plural form of translation for the given string in the given context.
// Supports optional parameters (vars... interface{}) to be inserted on the formatted string using the fmt.Printf syntax.
func (po *Po) GetNC(str, plural string, n int, ctx string, vars ...interface{}) string {
	// Sync read
	po.RLock()
	defer po.RUnlock()

	if po.contexts != nil {
		if _, ok := po.contexts[ctx]; ok {
			if po.contexts[ctx] != nil {
				if _, ok := po.contexts[ctx][str]; ok {
					return fmt.Sprintf(po.contexts[ctx][str].getN(po.pluralForm(n)), vars...)
				}
			}
		}
	}

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