// Copyright (c) 2012-present The upper.io/db authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

package postgresql

import (
	"fmt"
	"net"
	"net/url"
	"sort"
	"strings"
	"time"
	"unicode"
)

// scanner implements a tokenizer for libpq-style option strings.
type scanner struct {
	s []rune
	i int
}

// Next returns the next rune.  It returns 0, false if the end of the text has
// been reached.
func (s *scanner) Next() (rune, bool) {
	if s.i >= len(s.s) {
		return 0, false
	}
	r := s.s[s.i]
	s.i++
	return r, true
}

// SkipSpaces returns the next non-whitespace rune.  It returns 0, false if the
// end of the text has been reached.
func (s *scanner) SkipSpaces() (rune, bool) {
	r, ok := s.Next()
	for unicode.IsSpace(r) && ok {
		r, ok = s.Next()
	}
	return r, ok
}

type values map[string]string

func (vs values) Set(k, v string) {
	vs[k] = v
}

func (vs values) Get(k string) (v string) {
	return vs[k]
}

func (vs values) Isset(k string) bool {
	_, ok := vs[k]
	return ok
}

// ConnectionURL represents a parsed PostgreSQL connection URL.
//
// You can use a ConnectionURL struct as an argument for Open:
//
//   var settings = postgresql.ConnectionURL{
//     Host:       "localhost",          // PostgreSQL server IP or name.
//     Database:   "peanuts",            // Database name.
//     User:       "cbrown",             // Optional user name.
//     Password:   "snoopy",             // Optional user password.
//   }
//
//   sess, err = postgresql.Open(settings)
//
// If you already have a valid DSN, you can use ParseURL to convert it into
// a ConnectionURL before passing it to Open.
type ConnectionURL struct {
	User     string
	Password string
	Host     string
	Socket   string
	Database string
	Options  map[string]string

	timezone *time.Location
}

var escaper = strings.NewReplacer(` `, `\ `, `'`, `\'`, `\`, `\\`)

// ParseURL parses the given DSN into a ConnectionURL struct.
// A typical PostgreSQL connection URL looks like:
//
//   postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=verify-full
func ParseURL(s string) (u *ConnectionURL, err error) {
	o := make(values)

	if strings.HasPrefix(s, "postgres://") || strings.HasPrefix(s, "postgresql://") {
		s, err = parseURL(s)
		if err != nil {
			return u, err
		}
	}

	if err := parseOpts(s, o); err != nil {
		return u, err
	}
	u = &ConnectionURL{}

	u.User = o.Get("user")
	u.Password = o.Get("password")

	h := o.Get("host")
	p := o.Get("port")

	if strings.HasPrefix(h, "/") {
		u.Socket = h
	} else {
		if p == "" {
			u.Host = h
		} else {
			u.Host = fmt.Sprintf("%s:%s", h, p)
		}
	}

	u.Database = o.Get("dbname")

	u.Options = make(map[string]string)

	for k := range o {
		switch k {
		case "user", "password", "host", "port", "dbname":
			// Skip
		default:
			u.Options[k] = o[k]
		}
	}

	if timezone, ok := u.Options["timezone"]; ok {
		u.timezone, _ = time.LoadLocation(timezone)
	}

	return u, err
}

// parseOpts parses the options from name and adds them to the values.
//
// The parsing code is based on conninfo_parse from libpq's fe-connect.c
func parseOpts(name string, o values) error {
	s := newScanner(name)

	for {
		var (
			keyRunes, valRunes []rune
			r                  rune
			ok                 bool
		)

		if r, ok = s.SkipSpaces(); !ok {
			break
		}

		// Scan the key
		for !unicode.IsSpace(r) && r != '=' {
			keyRunes = append(keyRunes, r)
			if r, ok = s.Next(); !ok {
				break
			}
		}

		// Skip any whitespace if we're not at the = yet
		if r != '=' {
			r, ok = s.SkipSpaces()
		}

		// The current character should be =
		if r != '=' || !ok {
			return fmt.Errorf(`missing "=" after %q in connection info string"`, string(keyRunes))
		}

		// Skip any whitespace after the =
		if r, ok = s.SkipSpaces(); !ok {
			// If we reach the end here, the last value is just an empty string as per libpq.
			o.Set(string(keyRunes), "")
			break
		}

		if r != '\'' {
			for !unicode.IsSpace(r) {
				if r == '\\' {
					if r, ok = s.Next(); !ok {
						return fmt.Errorf(`missing character after backslash`)
					}
				}
				valRunes = append(valRunes, r)

				if r, ok = s.Next(); !ok {
					break
				}
			}
		} else {
		quote:
			for {
				if r, ok = s.Next(); !ok {
					return fmt.Errorf(`unterminated quoted string literal in connection string`)
				}
				switch r {
				case '\'':
					break quote
				case '\\':
					r, _ = s.Next()
					fallthrough
				default:
					valRunes = append(valRunes, r)
				}
			}
		}

		o.Set(string(keyRunes), string(valRunes))
	}

	return nil
}

// newScanner returns a new scanner initialized with the option string s.
func newScanner(s string) *scanner {
	return &scanner{[]rune(s), 0}
}

// ParseURL no longer needs to be used by clients of this library since supplying a URL as a
// connection string to sql.Open() is now supported:
//
//	sql.Open("postgres", "postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=verify-full")
//
// It remains exported here for backwards-compatibility.
//
// ParseURL converts a url to a connection string for driver.Open.
// Example:
//
//	"postgres://bob:secret@1.2.3.4:5432/mydb?sslmode=verify-full"
//
// converts to:
//
//	"user=bob password=secret host=1.2.3.4 port=5432 dbname=mydb sslmode=verify-full"
//
// A minimal example:
//
//	"postgres://"
//
// This will be blank, causing driver.Open to use all of the defaults
//
// NOTE: vendored/copied from github.com/lib/pq
func parseURL(uri string) (string, error) {
	u, err := url.Parse(uri)
	if err != nil {
		return "", err
	}

	if u.Scheme != "postgres" && u.Scheme != "postgresql" {
		return "", fmt.Errorf("invalid connection protocol: %s", u.Scheme)
	}

	var kvs []string
	escaper := strings.NewReplacer(` `, `\ `, `'`, `\'`, `\`, `\\`)
	accrue := func(k, v string) {
		if v != "" {
			kvs = append(kvs, k+"="+escaper.Replace(v))
		}
	}

	if u.User != nil {
		v := u.User.Username()
		accrue("user", v)

		v, _ = u.User.Password()
		accrue("password", v)
	}

	if host, port, err := net.SplitHostPort(u.Host); err != nil {
		accrue("host", u.Host)
	} else {
		accrue("host", host)
		accrue("port", port)
	}

	if u.Path != "" {
		accrue("dbname", u.Path[1:])
	}

	q := u.Query()
	for k := range q {
		accrue(k, q.Get(k))
	}

	sort.Strings(kvs) // Makes testing easier (not a performance concern)
	return strings.Join(kvs, " "), nil
}