// Package query provides tools for searching over structured keys.
//
// One example of such a structured key is a Trace id. A key is simply a
// string, but with a very specific format.  The parameters are serialized so
// that the parameter names appear in alphabetical order, and each name=value
// pair is delimited by a comma. For example, this map:
//
//  a := map[string]string{"d": "w", "a": "b", "c": "d"}
//
// Would be serialized as this key:
//
//   ,a=b,c=d,d=w,
//
// Structured keys are a serialization of a map[string]string, so duplicate
// parameter names are not allowed.
//
// Structured key parameter names and values are restricted to the following
// chars:
//
//   [a-zA-Z0-9._-]
//
package query

import (
	"errors"
	"fmt"
	"net/url"
	"regexp"
	"sort"
	"strconv"
	"strings"

	"go.skia.org/infra/go/paramtools"
	"go.skia.org/infra/go/skerr"
	"go.skia.org/infra/go/util"
)

var (
	invalidChar = regexp.MustCompile("([^a-zA-Z0-9._\\-])")
	keyRe       = regexp.MustCompile("^,([a-zA-Z0-9._\\-]+=[a-zA-Z0-9._\\-]+,)+$")
	paramRe     = regexp.MustCompile("^[a-zA-Z0-9._\\-]+$")

	QueryWillNeverMatch = errors.New("Query will never match.")
)

func clean(s string) string {
	return invalidChar.ReplaceAllLiteralString(s, "_")
}

// ForceValid ensures that the resulting map will make a valid structured key.
func ForceValid(m map[string]string) map[string]string {
	ret := make(map[string]string, len(m))
	for key, value := range m {
		ret[clean(key)] = clean(value)
	}

	return ret
}

// ValidateParamSet validates that all the keys and values in a ParamSet are
// restricted to the right subset of characters.
func ValidateParamSet(ps paramtools.ParamSet) error {
	for key, values := range ps {
		if !paramRe.MatchString(key) {
			return skerr.Fmt("Invalid key in ParamSet: %q", key)
		}
		for _, value := range values {
			if !paramRe.MatchString(value) {
				return skerr.Fmt("Invalid value in ParamSet: %q", value)
			}
		}
	}
	return nil
}

// ValidateKey returns true if a key is valid, i.e. if the parameter names are
// in alphabetical order and if the param names and values are restricted to
// valid values.
func ValidateKey(key string) bool {
	if !keyRe.MatchString(key) {
		return false
	}
	parts := strings.Split(key, ",")
	if len(parts) < 3 {
		return true
	}
	parts = parts[1 : len(parts)-1]
	if !sort.IsSorted(sort.StringSlice(parts)) {
		return false
	}
	lastName := ""
	for _, s := range parts {
		pair := strings.Split(s, "=")
		if len(pair) != 2 {
			return false
		}
		if lastName == pair[0] {
			return false
		}
		lastName = pair[0]
	}
	return true
}

// MakeKey returns a structured key from the given map[string]string, or a
// non-nil error if the parameter names or values violate the structured key
// restrictions.
func MakeKey(m map[string]string) (string, error) {
	if len(m) == 0 {
		return "", fmt.Errorf("Map must have at least one entry.")
	}
	keys := make([]string, 0, len(m))
	for k := range m {
		if !paramRe.MatchString(k) {
			return "", fmt.Errorf("Key contains invalid characters: %q", k)
		}
		keys = append(keys, k)
	}
	sort.Strings(keys)
	ret := ","
	for _, k := range keys {
		if !paramRe.MatchString(m[k]) {
			return "", fmt.Errorf("Value contains invalid characters: %q", m[k])
		}
		ret += fmt.Sprintf("%s=%s,", k, m[k])
	}
	return ret, nil
}

// MakeKeyFast returns a structured key from the given map[string]string. It
// does no validation on names or values. This is important if you are making
// keys from a large number of go routines, as regexp doesn't handle that case
// very well. See https://github.com/golang/go/issues/8232.
func MakeKeyFast(m map[string]string) (string, error) {
	if len(m) == 0 {
		return "", skerr.Fmt("Map must have at least one entry.")
	}
	ret := strings.Builder{}
	// Give a heuristic for the size based on the number of entries
	// most real-world entries are tens of bytes long, but this is a good
	// starting point.
	ret.Grow(len(m) * 20)
	ret.WriteRune(',')
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	for _, k := range keys {
		ret.WriteString(k)
		ret.WriteRune('=')
		ret.WriteString(m[k])
		ret.WriteRune(',')
	}
	return ret.String(), nil
}

// ParseKey parses the structured key, and if valid, returns the parsed values
// as a map[string]string, otherwise is returns a non-nil error.
func ParseKey(key string) (map[string]string, error) {
	if !keyRe.MatchString(key) {
		return nil, fmt.Errorf("Key is not valid, fails to match regex: %s", key)
	}
	ret := map[string]string{}
	parts := strings.Split(key, ",")
	if len(parts) < 3 {
		// Maybe should be an error?
		return map[string]string{}, nil
	}
	parts = parts[1 : len(parts)-1]
	if !sort.IsSorted(sort.StringSlice(parts)) {
		return nil, fmt.Errorf("Key is not valid, params are unsorted: %v", parts)
	}
	lastName := ""
	for _, s := range parts {
		pair := strings.Split(s, "=")
		if len(pair) != 2 {
			return nil, fmt.Errorf("Invalid key=value pair: %s", s)
		}
		if lastName == pair[0] {
			return nil, fmt.Errorf("Duplicate key: %s", s)
		}
		ret[pair[0]] = pair[1]
		lastName = pair[0]
	}
	return ret, nil
}

// ParseKeyFast is like ParseKey but omits much of the validation portions
func ParseKeyFast(key string) (map[string]string, error) {
	ret := map[string]string{}
	parts := strings.Split(key, ",")
	if len(parts) < 3 {
		return map[string]string{}, nil
	}
	parts = parts[1 : len(parts)-1]

	for _, s := range parts {
		pair := strings.SplitN(s, "=", 2)
		if len(pair) != 2 {
			return nil, fmt.Errorf("Invalid key=value pair: %s", s)
		}
		ret[pair[0]] = pair[1]
	}
	return ret, nil
}

// queryParam represents a query on a particular parameter in a key.
type queryParam struct {
	keyMatch    string         // The param key, including the leading "," and trailing "=".
	keyMatchLen int            // The length of keyMatch.
	isWildCard  bool           // True if this is a wildcard value match.
	isRegex     bool           // True if this is a regex value match.
	isNegative  bool           // True if this is a negative value match.
	values      []string       // The potential matches for the value.
	reg         *regexp.Regexp // The regexp to match against, if a regexp search.
}

// Query represents a query against a key, i.e. Query.Matches can return true
// or false if a given key matches the query. For example, this query will find all
// keys that have a value of 565 for 'config' and true for 'debug':
//
//		q := New(url.Values{"config": []string{"565"}, "debug": []string{"true"}})
//
// This will find all keys that have a value of '565' or '8888':
//
//		q := New(url.Values{"config": []string{"565", "8888"}})
//
// If the first parameter value is preceeded with an '!' then the match is negated,
// i.e. this query will match all keys that have a 'config' param, but whose value
// is not '565'.
//
//		q := New(url.Values{"config": []string{"!565"}})
//
// If the parameter value is '*' then the match will match all keys that have
// that parameter name. I.e. this will match all keys that have a parameter
// named 'config', regardless of the value:
//
//		q := New(url.Values{"config": []string{"*"}})
//
// If the parameter value begins with '~' then the rest of the value is interpreted
// as a regular expression. I.e. this will match all keys that have a parameter
// named 'arch' that begin with 'x':
//
//		q := New(url.Values{"arch": []string{"~^x"}})
//
//
// Here is more complex example that matches all tests that have the 'name'
// parameter with a value of 'desk_nytimes.skp', a 'config' param that does not
// equal '565' or '8888', and has an 'extra_config' parameter of any value.
//
//	  q := New(url.Values{
//        "name": "desk_nytimes.skp",
//        "config": []string{"!565", "8888"},
//        "extra_config": []string{"*"}})
//
type Query struct {
	// These are in alphabetical order of parameter name.
	params []queryParam
}

// String returns a minimal string representation of the Query.
func (q *Query) String() string {
	ret := []string{}
	for _, p := range q.params {
		ret = append(ret, p.values...)
		ret = append(ret, " ")
	}
	return strings.Join(ret, "")
}

// NewFromString creates a Query from the given string, which is formatted as a URL query.
func NewFromString(s string) (*Query, error) {
	values, err := url.ParseQuery(s)
	if err != nil {
		return nil, err
	}
	return New(values)
}

// New creates a Query from the given url.Values. It represents a query to be
// used against keys.
func New(q url.Values) (*Query, error) {
	keys := make([]string, 0, len(q))
	for k := range q {
		keys = append(keys, k)
	}
	sort.Strings(keys)

	params := make([]queryParam, 0, len(q))
	for _, key := range keys {
		keyMatch := "," + key + "="
		isWildCard := false
		isRegex := false
		isNegative := false
		values := q[key]
		var reg *regexp.Regexp
		var err error
		// Is this param query a wildcard?
		if len(q[key]) == 1 {
			if q[key][0] == "" {
				return nil, fmt.Errorf("Invalid query")
			}
			if q[key][0] == "*" {
				isWildCard = true
			}
			if q[key][0][:1] == "~" {
				isRegex = true
				reg, err = regexp.Compile(q[key][0][1:])
				if err != nil {
					return nil, fmt.Errorf("Error compiling regexp %q: %s", q[key][0][1:], err)
				}
			}
		}
		// Is this param query a negative match?
		if len(q[key]) >= 1 {
			if strings.HasPrefix(q[key][0], "!") {
				isNegative = true
				values = []string{}
				for _, v := range q[key] {
					if strings.HasPrefix(v, "!") {
						values = append(values, v[1:])
					} else {
						values = append(values, v)
					}
				}
			}
		}
		params = append(params, queryParam{
			keyMatch:    keyMatch,
			keyMatchLen: len(keyMatch),
			isWildCard:  isWildCard,
			isRegex:     isRegex,
			isNegative:  isNegative,
			values:      values,
			reg:         reg,
		})
	}

	return &Query{params: params}, nil
}

// Empty returns true of the Query is empty, i.e. it will match any trace.
func (q *Query) Empty() bool {
	return len(q.params) == 0
}

// Matches returns true if the given structured key matches the query.
func (q *Query) Matches(s string) bool {
	// Search forward in the given structured key. Since q.params are in
	// alphabetical order and structured keys have their params in alphabetical
	// order we can always search forward in the structured key, i.e. once
	// we've matched to a certain index in the string we can shorten the string
	// and only search the remaining chars.
	for _, part := range q.params {
		//  First find the key.
		keyIndex := strings.Index(s, part.keyMatch)
		if keyIndex == -1 {
			return false
		}
		// Truncate to the key.
		s = s[keyIndex+part.keyMatchLen:]
		if part.isWildCard {
			continue
		}
		// Extract the value string.
		valueIndex := strings.Index(s, ",")
		value := s[:valueIndex]
		if part.isRegex {
			if !part.reg.MatchString(value) {
				return false
			}
		} else if part.isNegative == util.In(value, part.values) {
			return false
		}
		// Truncate to the value.
		s = s[valueIndex:]
	}
	return true
}

// appendRegexForFilter will attach a regex to 'ret' for every value in
// 'values' that matches the given 'filter'.
func appendRegexForFilter(keyIndex string, values []string, part queryParam, ret *[]string, filter func(string) bool) error {
	toBeORd := []string{}
	for index, value := range values {
		if filter(value) {
			toBeORd = append(toBeORd, fmt.Sprintf(`(,%s=%s\b)`, keyIndex, strconv.Itoa(index)))
		}
	}
	if len(toBeORd) == 0 {
		return QueryWillNeverMatch
	}
	*ret = append(*ret, "(", strings.Join(toBeORd, "|"), ").*")
	return nil
}

// appendValueForFilter will return the values that matches the given 'filter'.
func appendValueForFilter(key string, values []string, part queryParam, ret *paramtools.ParamSet, filter func(string) bool) error {
	toBeORd := []string{}
	for _, value := range values {
		if filter(value) {
			toBeORd = append(toBeORd, value)
		}
	}
	if len(toBeORd) == 0 {
		return QueryWillNeverMatch
	}
	(*ret)[key] = toBeORd
	return nil
}

// QueryPlan returns a paramtools.ParamSet that can be used run a query using
// trace indices.
//
// That is, if you have a Params:
//
//    Params{"config":"8888", "arch":"x86"}
//
// And a ParamSet:
//
//    ps := &paramtools.ParamSet{
//    	ParamSet: paramtools.ParamSet{
//    	  "config": []string{"565", "8888", "gpu"},
//    	  "arch":   []string{"x86", "arm", "riscv"},
//        "foo":    []string{"bar"},
//    	},
//    }
//
// It would return the ParamSet:
//
//    ParamSet{
//      "config": ["8888"],
//      "arch":   ["x86"],
//    }
//
// Then a query of the form:
//
//    url.Values{"arch": []string{"x86", "risc-v"}, "config": []string{"*"}}
//
// Would return:
//
//    ParamSet{
//      "arch": ["x86", "risc-v"],
//      "config": ["8888", "565", "gpu"],
//    }
//
func (q *Query) QueryPlan(ps paramtools.ReadOnlyParamSet) (paramtools.ParamSet, error) {
	ret := paramtools.NewParamSet()
	// Loop over KeyOrder, we don't care about the q.params order.
	for key := range ps {
		for _, part := range q.params {
			// Strip the , and = from part.keyMatch.
			partKey := part.keyMatch[1 : len(part.keyMatch)-1]
			if partKey == key {
				// WildCard, Regex and Negative are all mutually exclusive.
				values := ps[key]
				var err error = nil
				if part.isWildCard {
					ret[key] = append([]string{}, ps[key]...)
				} else if part.isRegex {
					err = appendValueForFilter(key, values, part, &ret, func(value string) bool {
						return part.reg.MatchString(value)
					})
				} else if part.isNegative {
					err = appendValueForFilter(key, values, part, &ret, func(value string) bool {
						return !util.In(value, part.values)
					})
				} else {
					err = appendValueForFilter(key, values, part, &ret, func(value string) bool {
						return util.In(value, part.values)
					})
				}
				if err != nil {
					return nil, err
				}
				continue
			}
		}
	}
	return ret, nil
}