package fic

import (
	"bytes"
	"errors"
	"fmt"
	"regexp"
	"time"

	"golang.org/x/crypto/blake2b"
)

// FlagKey represents a flag's challenge, stored as hash.
type FlagKey struct {
	Id              int64   `json:"id"`
	// IdExercice is the identifier of the underlying challenge
	IdExercice      int64   `json:"idExercice"`
	// Label is the title of the flag as displayed to players
	Label           string  `json:"label"`
	// Help is a small piece of text that aims to add useful information like flag format, ...
	Help            string  `json:"help"`
	// IgnoreCase indicates if the case is sensitive to case or not
	IgnoreCase      bool    `json:"ignorecase"`
	// ValidatorRegexp extracts a subset of the player's answer, that will be checked.
	ValidatorRegexp *string `json:"validator_regexp"`
	// Checksum is the expected hashed flag
	Checksum        []byte  `json:"value"`
	// ChoicesCost is the number of points lost to display choices.
	ChoicesCost     int64   `json:"choices_cost"`
}

// GetFlagKeys returns a list of key's flags comming with the challenge.
func (e Exercice) GetFlagKeys() ([]FlagKey, error) {
	if rows, err := DBQuery("SELECT id_flag, id_exercice, type, help, ignorecase, validator_regexp, cksum, choices_cost FROM exercice_flags WHERE id_exercice = ?", e.Id); err != nil {
		return nil, err
	} else {
		defer rows.Close()

		var flags = make([]FlagKey, 0)
		for rows.Next() {
			var k FlagKey
			k.IdExercice = e.Id

			if err := rows.Scan(&k.Id, &k.IdExercice, &k.Label, &k.Help, &k.IgnoreCase, &k.ValidatorRegexp, &k.Checksum, &k.ChoicesCost); err != nil {
				return nil, err
			}

			flags = append(flags, k)
		}
		if err := rows.Err(); err != nil {
			return nil, err
		}

		return flags, nil
	}
}

// GetFlagKey returns a list of flags comming with the challenge.
func GetFlagKey(id int64) (k FlagKey, err error) {
	err = DBQueryRow("SELECT id_flag, id_exercice, type, help, ignorecase, validator_regexp, cksum, choices_cost FROM exercice_flags WHERE id_flag = ?", id).Scan(&k.Id, &k.IdExercice, &k.Label, &k.Help, &k.IgnoreCase, &k.ValidatorRegexp, &k.Checksum, &k.ChoicesCost)
	return
}

// GetFlagKeyByLabel returns a flag matching the given label.
func (e Exercice) GetFlagKeyByLabel(label string) (k FlagKey, err error) {
	err = DBQueryRow("SELECT id_flag, id_exercice, type, help, ignorecase, validator_regexp, cksum, choices_cost FROM exercice_flags WHERE type LIKE ? AND id_exercice = ?", label, e.Id).Scan(&k.Id, &k.IdExercice, &k.Label, &k.Help, &k.IgnoreCase, &k.ValidatorRegexp, &k.Checksum, &k.ChoicesCost)
	return
}

// getHashedFlag calculates the expected checksum for the given raw_value.
func getHashedFlag(raw_value []byte) [blake2b.Size]byte {
	hash := blake2b.Sum512(raw_value)
	return hash
}

func ExecValidatorRegexp(vre string, val []byte) ([]byte, error) {
	if re, err := regexp.Compile(vre); err != nil {
		return val, err
	} else if res := re.FindSubmatch(val); res == nil {
		return val, errors.New("Expected flag doesn't pass through the validator_regexp")
	} else {
		return bytes.Join(res[1:], []byte("+")), nil
	}
}

// AddRawFlagKey creates and fills a new struct FlagKey, from a non-hashed flag, and registers it into the database.
func (e Exercice) AddRawFlagKey(name string, help string, ignorecase bool, validator_regexp *string, raw_value []byte, choicescost int64) (FlagKey, error) {
	if ignorecase {
		raw_value = bytes.ToLower(raw_value)
	}

	// Check that raw value passes through the regexp
	if validator_regexp != nil {
		var err error
		if raw_value, err = ExecValidatorRegexp(*validator_regexp, raw_value); err != nil {
			return FlagKey{}, err
		}
	}

	hash := getHashedFlag(raw_value)
	return e.AddFlagKey(name, help, ignorecase, validator_regexp, hash[:], choicescost)
}

// AddFlagKey creates and fills a new struct Flag, from a hashed flag, and registers it into the database.
func (e Exercice) AddFlagKey(name string, help string, ignorecase bool, validator_regexp *string, checksum []byte, choicescost int64) (FlagKey, error) {
	// Check the regexp compile
	if validator_regexp != nil {
		if _, err := regexp.Compile(*validator_regexp); err != nil {
			return FlagKey{}, err
		}
	}

	if res, err := DBExec("INSERT INTO exercice_flags (id_exercice, type, help, ignorecase, validator_regexp, cksum, choices_cost) VALUES (?, ?, ?, ?, ?, ?, ?)", e.Id, name, help, ignorecase, validator_regexp, checksum, choicescost); err != nil {
		return FlagKey{}, err
	} else if kid, err := res.LastInsertId(); err != nil {
		return FlagKey{}, err
	} else {
		return FlagKey{kid, e.Id, name, help, ignorecase, validator_regexp, checksum, choicescost}, nil
	}
}

// Update applies modifications back to the database.
func (k FlagKey) Update() (int64, error) {
	if k.ValidatorRegexp != nil {
		if _, err := regexp.Compile(*k.ValidatorRegexp); err != nil {
			return 0, err
		}
	}

	if res, err := DBExec("UPDATE exercice_flags SET id_exercice = ?, type = ?, help = ?, ignorecase = ?, validator_regexp = ?, cksum = ?, choices_cost = ? WHERE id_flag = ?", k.IdExercice, k.Label, k.Help, k.IgnoreCase, k.ValidatorRegexp, k.Checksum, k.ChoicesCost, k.Id); err != nil {
		return 0, err
	} else if nb, err := res.RowsAffected(); err != nil {
		return 0, err
	} else {
		return nb, err
	}
}

// Delete the flag from the database.
func (k FlagKey) Delete() (int64, error) {
	if _, err := DBExec("DELETE FROM exercice_files_deps WHERE id_flag = ?", k.Id); err != nil {
		return 0, err
	} else if _, err := DBExec("DELETE FROM exercice_mcq_okey_deps WHERE id_flag_dep = ?", k.Id); err != nil {
		return 0, err
	} else if _, err := DBExec("DELETE FROM exercice_flags_omcq_deps WHERE id_flag = ?", k.Id); err != nil {
		return 0, err
	} else if _, err := DBExec("DELETE FROM exercice_flags_deps WHERE id_flag = ? OR id_flag_dep = ?", k.Id, k.Id); err != nil {
		return 0, err
	} else if _, err := DBExec("DELETE FROM flag_choices WHERE id_flag = ?", k.Id); err != nil {
		return 0, err
	} else if res, err := DBExec("DELETE FROM exercice_flags WHERE id_flag = ?", k.Id); err != nil {
		return 0, err
	} else if nb, err := res.RowsAffected(); err != nil {
		return 0, err
	} else {
		return nb, err
	}
}

// AddDepend insert a new dependency to a given flag.
func (k FlagKey) AddDepend(j Flag) (err error) {
	if d, ok := j.(FlagKey); ok {
		_, err = DBExec("INSERT INTO exercice_flags_deps (id_flag, id_flag_dep) VALUES (?, ?)", k.Id, d.Id)
	} else if d, ok := j.(MCQ); ok {
		_, err = DBExec("INSERT INTO exercice_flags_omcq_deps (id_flag, id_mcq_dep) VALUES (?, ?)", k.Id, d.Id)
	} else {
		err = errors.New(fmt.Sprintf("Dependancy type for key (%T) not implemented for this flag.", j))
	}
	return
}

// GetDepends retrieve the flag's dependency list.
func (k FlagKey) GetDepends() ([]Flag, error) {
	var deps = make([]Flag, 0)

	if rows, err := DBQuery("SELECT id_flag_dep FROM exercice_flags_deps WHERE id_flag = ?", k.Id); err != nil {
		return nil, err
	} else {
		defer rows.Close()

		for rows.Next() {
			var d int64
			if err := rows.Scan(&d); err != nil {
				return nil, err
			}
			deps = append(deps, FlagKey{Id: d, IdExercice: k.IdExercice})
		}
		if err := rows.Err(); err != nil {
			return nil, err
		}
	}

	if rows, err := DBQuery("SELECT id_mcq_dep FROM exercice_flags_omcq_deps WHERE id_flag = ?", k.Id); err != nil {
		return nil, err
	} else {
		defer rows.Close()

		for rows.Next() {
			var d int64
			if err := rows.Scan(&d); err != nil {
				return nil, err
			}
			deps = append(deps, MCQ{Id: d, IdExercice: k.IdExercice})
		}
		if err := rows.Err(); err != nil {
			return nil, err
		}
	}

	return deps, nil
}

// Check if the given val is the expected one for this flag.
func (k FlagKey) Check(v interface{}) int {
	var val []byte

	if va, ok := v.([]byte); !ok {
		return -1
	} else {
		val = va
	}

	if k.IgnoreCase {
		val = bytes.ToLower(val)
	}

	// Check that raw value passes through the regexp
	if k.ValidatorRegexp != nil {
		val, _ = ExecValidatorRegexp(*k.ValidatorRegexp, val)
	}

	// Check that the value is not empty
	if len(val) == 0 {
		return 1
	}

	hash := getHashedFlag(val)
	if len(k.Checksum) != len(hash) {
		return 1
	}

	for i := range hash {
		if k.Checksum[i] != hash[i] {
			return 1
		}
	}

	return 0
}

// FoundBy registers in the database that the given Team solved the flag.
func (k FlagKey) FoundBy(t Team) {
	DBExec("INSERT INTO flag_found (id_flag, id_team, time) VALUES (?, ?, ?)", k.Id, t.Id, time.Now())
}