package iam

import (
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"

	policyengine "git.frostfs.info/TrueCloudLab/policy-engine"
)

const (
	FrostFSPrincipal = "FrostFS"

	RequestOwnerProperty = "Owner"
)

const (
	// String condition operators.
	CondStringEquals              string = "StringEquals"
	CondStringNotEquals           string = "StringNotEquals"
	CondStringEqualsIgnoreCase    string = "StringEqualsIgnoreCase"
	CondStringNotEqualsIgnoreCase string = "StringNotEqualsIgnoreCase"
	CondStringLike                string = "StringLike"
	CondStringNotLike             string = "StringNotLike"

	// Numeric condition operators.
	CondNumericEquals            string = "NumericEquals"
	CondNumericNotEquals         string = "NumericNotEquals"
	CondNumericLessThan          string = "NumericLessThan"
	CondNumericLessThanEquals    string = "NumericLessThanEquals"
	CondNumericGreaterThan       string = "NumericGreaterThan"
	CondNumericGreaterThanEquals string = "NumericGreaterThanEquals"

	// Date condition operators.
	CondDateEquals            string = "DateEquals"
	CondDateNotEquals         string = "DateNotEquals"
	CondDateLessThan          string = "DateLessThan"
	CondDateLessThanEquals    string = "DateLessThanEquals"
	CondDateGreaterThan       string = "DateGreaterThan"
	CondDateGreaterThanEquals string = "DateGreaterThanEquals"

	// Bolean condition operators.
	CondBool string = "Bool"

	// IP address condition operators.
	CondIPAddress    string = "IpAddress"
	CondNotIPAddress string = "NotIpAddress"

	// ARN condition operators.
	CondArnEquals    string = "ArnEquals"
	CondArnLike      string = "ArnLike"
	CondArnNotEquals string = "ArnNotEquals"
	CondArnNotLike   string = "ArnNotLike"
)

func (p Policy) ToChain() (*policyengine.Chain, error) {
	var chain policyengine.Chain

	for _, statement := range p.Statement {
		status := policyengine.AccessDenied
		if statement.Effect == AllowEffect {
			status = policyengine.Allow
		}

		if len(statement.Principal) != 1 {
			return nil, errors.New("currently supported exactly one principal type")
		}

		var principals []string
		var op policyengine.ConditionType
		if _, ok := statement.Principal[Wildcard]; ok {
			principals = []string{Wildcard}
			op = policyengine.CondStringLike
		} else if frostfsPrincipals, ok := statement.Principal[FrostFSPrincipal]; ok {
			principals = frostfsPrincipals
			op = policyengine.CondStringEquals
		} else {
			return nil, errors.New("currently supported only FrostFS or all (wildcard) principals")
		}

		var conditions []policyengine.Condition
		for _, principal := range principals {
			conditions = append(conditions, policyengine.Condition{
				Op:     op,
				Object: policyengine.ObjectRequest,
				Key:    RequestOwnerProperty,
				Value:  principal,
			})
		}

		conds, err := statement.Conditions.ToChainCondition()
		if err != nil {
			return nil, err
		}
		conditions = append(conditions, conds...)

		r := policyengine.Rule{
			Status:    status,
			Action:    statement.Action,
			Resource:  statement.Resource,
			Any:       true,
			Condition: conditions,
		}
		chain.Rules = append(chain.Rules, r)
	}

	return &chain, nil
}

//nolint:funlen
func (c Conditions) ToChainCondition() ([]policyengine.Condition, error) {
	var conditions []policyengine.Condition

	var convertValue convertFunction

	for op, KVs := range c {
		var condType policyengine.ConditionType

		switch {
		case strings.HasPrefix(op, "String"):
			convertValue = noConvertFunction
			switch op {
			case CondStringEquals:
				condType = policyengine.CondStringEquals
			case CondStringNotEquals:
				condType = policyengine.CondStringNotEquals
			case CondStringEqualsIgnoreCase:
				condType = policyengine.CondStringEqualsIgnoreCase
			case CondStringNotEqualsIgnoreCase:
				condType = policyengine.CondStringNotEqualsIgnoreCase
			case CondStringLike:
				condType = policyengine.CondStringLike
			case CondStringNotLike:
				condType = policyengine.CondStringNotLike
			default:
				return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
			}
		case strings.HasPrefix(op, "Arn"):
			convertValue = noConvertFunction
			switch op {
			case CondArnEquals:
				condType = policyengine.CondStringEquals
			case CondArnNotEquals:
				condType = policyengine.CondStringNotEquals
			case CondArnLike:
				condType = policyengine.CondStringLike
			case CondArnNotLike:
				condType = policyengine.CondStringNotLike
			default:
				return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
			}
		case strings.HasPrefix(op, "Numeric"):
			// TODO
		case strings.HasPrefix(op, "Date"):
			convertValue = dateConvertFunction
			switch op {
			case CondDateEquals:
				condType = policyengine.CondStringEquals
			case CondDateNotEquals:
				condType = policyengine.CondStringNotEquals
			case CondDateLessThan:
				condType = policyengine.CondStringLessThan
			case CondDateLessThanEquals:
				condType = policyengine.CondStringLessThanEquals
			case CondDateGreaterThan:
				condType = policyengine.CondStringGreaterThan
			case CondDateGreaterThanEquals:
				condType = policyengine.CondStringGreaterThanEquals
			default:
				return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
			}
		case op == CondBool:
			convertValue = noConvertFunction
			condType = policyengine.CondStringEqualsIgnoreCase
		case op == CondIPAddress:
			// todo consider using converters
			//  "203.0.113.0/24" -> "203.0.113.*",
			//  "2001:DB8:1234:5678::/64" -> "2001:DB8:1234:5678:*"
			//  or having specific condition type for IP
			convertValue = noConvertFunction
			condType = policyengine.CondStringLike
		case op == CondNotIPAddress:
			convertValue = noConvertFunction
			condType = policyengine.CondStringNotLike
		default:
			return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
		}

		for key, values := range KVs {
			for _, val := range values {
				converted, err := convertValue(val)
				if err != nil {
					return nil, err
				}

				conditions = append(conditions, policyengine.Condition{
					Op:     condType,
					Object: policyengine.ObjectRequest,
					Key:    key,
					Value:  converted,
				})
			}
		}
	}

	return conditions, nil
}

type convertFunction func(string) (string, error)

func noConvertFunction(val string) (string, error) {
	return val, nil
}

func dateConvertFunction(val string) (string, error) {
	if _, err := strconv.ParseInt(val, 10, 64); err == nil {
		return val, nil
	}

	parsed, err := time.Parse(time.RFC3339, val)
	if err != nil {
		return "", err
	}

	return strconv.FormatInt(parsed.UTC().Unix(), 10), nil
}