// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package tools

import (
	"encoding/json"
	"fmt"

	"github.com/googleapis/genai-toolbox/internal/util"
)

const (
	typeString = "string"
	typeInt    = "integer"
	typeFloat  = "float"
	typeBool   = "boolean"
	typeArray  = "array"
)

// ParamValues is an ordered list of ParamValue
type ParamValues []ParamValue

// ParamValue represents the parameter's name and value.
type ParamValue struct {
	Name  string
	Value any
}

// AsSlice returns a slice of the Param's values (in order).
func (p ParamValues) AsSlice() []any {
	params := []any{}

	for _, p := range p {
		params = append(params, p.Value)
	}
	return params
}

// AsMap returns a map of ParamValue's names to values.
func (p ParamValues) AsMap() map[string]interface{} {
	params := make(map[string]interface{})
	for _, p := range p {
		params[p.Name] = p.Value
	}
	return params
}

// AsReversedMap returns a map of ParamValue's values to names.
func (p ParamValues) AsReversedMap() map[any]string {
	params := make(map[any]string)
	for _, p := range p {
		params[p.Value] = p.Name
	}
	return params
}

// AsMapByOrderedKeys returns a map of a key's position to it's value, as neccesary for Spanner PSQL.
// Example { $1 -> "value1", $2 -> "value2" }
func (p ParamValues) AsMapByOrderedKeys() map[string]interface{} {
	params := make(map[string]interface{})

	for i, p := range p {
		key := fmt.Sprintf("p%d", i+1)
		params[key] = p.Value
	}
	return params
}

func parseFromAuthSource(paramAuthSources []ParamAuthSource, claimsMap map[string]map[string]any) (any, error) {
	// parse a parameter from claims using its specified auth sources
	for _, a := range paramAuthSources {
		claims, ok := claimsMap[a.Name]
		if !ok {
			// not validated for this authsource, skip to the next one
			continue
		}
		v, ok := claims[a.Field]
		if !ok {
			// claims do not contain specified field
			return nil, fmt.Errorf("no field named %s in claims", a.Field)
		}
		return v, nil
	}
	return nil, fmt.Errorf("missing or invalid authentication header")
}

// ParseParams is a helper function for parsing Parameters from an arbitraryJSON object.
func ParseParams(ps Parameters, data map[string]any, claimsMap map[string]map[string]any) (ParamValues, error) {
	params := make([]ParamValue, 0, len(ps))
	for _, p := range ps {
		var v any
		paramAuthSources := p.GetAuthSources()
		name := p.GetName()
		if paramAuthSources == nil {
			// parse non auth-required parameter
			var ok bool
			v, ok = data[name]
			if !ok {
				return nil, fmt.Errorf("parameter %q is required", name)
			}
		} else {
			// parse authenticated parameter
			var err error
			v, err = parseFromAuthSource(paramAuthSources, claimsMap)
			if err != nil {
				return nil, fmt.Errorf("error parsing authenticated parameter %q: %w", name, err)
			}
		}
		newV, err := p.Parse(v)
		if err != nil {
			return nil, fmt.Errorf("unable to parse value for %q: %w", name, err)
		}
		params = append(params, ParamValue{Name: name, Value: newV})
	}
	return params, nil
}

type Parameter interface {
	// Note: It's typically not idiomatic to include "Get" in the function name,
	// but this is done to differentiate it from the fields in CommonParameter.
	GetName() string
	GetType() string
	GetAuthSources() []ParamAuthSource
	Parse(any) (any, error)
	Manifest() ParameterManifest
}

// Parameters is a type used to allow unmarshal a list of parameters
type Parameters []Parameter

func (c *Parameters) UnmarshalYAML(unmarshal func(interface{}) error) error {
	*c = make(Parameters, 0)
	// Parse the 'kind' fields for each source
	var rawList []util.DelayedUnmarshaler
	if err := unmarshal(&rawList); err != nil {
		return err
	}
	for _, u := range rawList {
		p, err := parseParamFromDelayedUnmarshaler(&u)
		if err != nil {
			return err
		}
		(*c) = append((*c), p)
	}
	return nil
}

// parseParamFromDelayedUnmarshaler is a helper function that is required to parse
// parameters because there are multiple different types
func parseParamFromDelayedUnmarshaler(u *util.DelayedUnmarshaler) (Parameter, error) {
	var p CommonParameter
	err := u.Unmarshal(&p)
	if err != nil {
		return nil, fmt.Errorf("parameter missing required fields: %w", err)
	}
	switch p.Type {
	case typeString:
		a := &StringParameter{}
		if err := u.Unmarshal(a); err != nil {
			return nil, fmt.Errorf("unable to parse as %q: %w", p.Type, err)
		}
		return a, nil
	case typeInt:
		a := &IntParameter{}
		if err := u.Unmarshal(a); err != nil {
			return nil, fmt.Errorf("unable to parse as %q: %w", p.Type, err)
		}
		return a, nil
	case typeFloat:
		a := &FloatParameter{}
		if err := u.Unmarshal(a); err != nil {
			return nil, fmt.Errorf("unable to parse as %q: %w", p.Type, err)
		}
		return a, nil
	case typeBool:
		a := &BooleanParameter{}
		if err := u.Unmarshal(a); err != nil {
			return nil, fmt.Errorf("unable to parse as %q: %w", p.Type, err)
		}
		return a, nil
	case typeArray:
		a := &ArrayParameter{}
		if err := u.Unmarshal(a); err != nil {
			return nil, fmt.Errorf("unable to parse as %q: %w", p.Type, err)
		}
		return a, nil
	}
	return nil, fmt.Errorf("%q is not valid type for a parameter!", p.Type)
}

func (ps Parameters) Manifest() []ParameterManifest {
	rtn := make([]ParameterManifest, 0, len(ps))
	for _, p := range ps {
		rtn = append(rtn, p.Manifest())
	}
	return rtn
}

// ParameterManifest represents parameters when served as part of a ToolManifest.
type ParameterManifest struct {
	Name        string   `json:"name"`
	Type        string   `json:"type"`
	Description string   `json:"description"`
	AuthSources []string `json:"authSources"`
	// Parameter   *ParameterManifest `json:"parameter,omitempty"`
}

// CommonParameter are default fields that are emebdding in most Parameter implementations. Embedding this stuct will give the object Name() and Type() functions.
type CommonParameter struct {
	Name        string            `yaml:"name"`
	Type        string            `yaml:"type"`
	Desc        string            `yaml:"description"`
	AuthSources []ParamAuthSource `yaml:"authSources"`
}

// GetName returns the name specified for the Parameter.
func (p *CommonParameter) GetName() string {
	return p.Name
}

// GetType returns the type specified for the Parameter.
func (p *CommonParameter) GetType() string {
	return p.Type
}

// GetType returns the type specified for the Parameter.
func (p *CommonParameter) Manifest() ParameterManifest {
	// only list ParamAuthSource names (without fields) in manifest
	authNames := make([]string, len(p.AuthSources))
	for i, a := range p.AuthSources {
		authNames[i] = a.Name
	}
	return ParameterManifest{
		Name:        p.Name,
		Type:        p.Type,
		Description: p.Desc,
		AuthSources: authNames,
	}
}

// ParseTypeError is a custom error for incorrectly typed Parameters.
type ParseTypeError struct {
	Name  string
	Type  string
	Value any
}

func (e ParseTypeError) Error() string {
	return fmt.Sprintf("%q not type %q", e.Value, e.Type)
}

type ParamAuthSource struct {
	Name  string `yaml:"name"`
	Field string `yaml:"field"`
}

// NewStringParameter is a convenience function for initializing a StringParameter.
func NewStringParameter(name, desc string) *StringParameter {
	return &StringParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeString,
			Desc:        desc,
			AuthSources: nil,
		},
	}
}

// NewStringParameterWithAuth is a convenience function for initializing a StringParameter with a list of ParamAuthSource.
func NewStringParameterWithAuth(name, desc string, authSources []ParamAuthSource) *StringParameter {
	return &StringParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeString,
			Desc:        desc,
			AuthSources: authSources,
		},
	}
}

var _ Parameter = &StringParameter{}

// StringParameter is a parameter representing the "string" type.
type StringParameter struct {
	CommonParameter `yaml:",inline"`
}

// Parse casts the value "v" as a "string".
func (p *StringParameter) Parse(v any) (any, error) {
	newV, ok := v.(string)
	if !ok {
		return nil, &ParseTypeError{p.Name, p.Type, v}
	}
	return newV, nil
}
func (p *StringParameter) GetAuthSources() []ParamAuthSource {
	return p.AuthSources
}

// NewIntParameter is a convenience function for initializing a IntParameter.
func NewIntParameter(name, desc string) *IntParameter {
	return &IntParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeInt,
			Desc:        desc,
			AuthSources: nil,
		},
	}
}

// NewIntParameterWithAuth is a convenience function for initializing a IntParameter with a list of ParamAuthSource.
func NewIntParameterWithAuth(name, desc string, authSources []ParamAuthSource) *IntParameter {
	return &IntParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeInt,
			Desc:        desc,
			AuthSources: authSources,
		},
	}
}

var _ Parameter = &IntParameter{}

// IntParameter is a parameter representing the "int" type.
type IntParameter struct {
	CommonParameter `yaml:",inline"`
}

func (p *IntParameter) Parse(v any) (any, error) {
	var out int
	switch newV := v.(type) {
	default:
		return nil, &ParseTypeError{p.Name, p.Type, v}
	case int:
		out = int(newV)
	case int32:
		out = int(newV)
	case int64:
		out = int(newV)
	case json.Number:
		newI, err := newV.Int64()
		if err != nil {
			return nil, &ParseTypeError{p.Name, p.Type, v}
		}
		out = int(newI)
	}
	return out, nil
}

func (p *IntParameter) GetAuthSources() []ParamAuthSource {
	return p.AuthSources
}

// NewFloatParameter is a convenience function for initializing a FloatParameter.
func NewFloatParameter(name, desc string) *FloatParameter {
	return &FloatParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeFloat,
			Desc:        desc,
			AuthSources: nil,
		},
	}
}

// NewFloatParameterWithAuth is a convenience function for initializing a FloatParameter with a list of ParamAuthSource.
func NewFloatParameterWithAuth(name, desc string, authSources []ParamAuthSource) *FloatParameter {
	return &FloatParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeFloat,
			Desc:        desc,
			AuthSources: authSources,
		},
	}
}

var _ Parameter = &FloatParameter{}

// FloatParameter is a parameter representing the "float" type.
type FloatParameter struct {
	CommonParameter `yaml:",inline"`
}

func (p *FloatParameter) Parse(v any) (any, error) {
	var out float64
	switch newV := v.(type) {
	default:
		return nil, &ParseTypeError{p.Name, p.Type, v}
	case float32:
		out = float64(newV)
	case float64:
		out = newV
	case json.Number:
		newI, err := newV.Float64()
		if err != nil {
			return nil, &ParseTypeError{p.Name, p.Type, v}
		}
		out = float64(newI)
	}
	return out, nil
}

func (p *FloatParameter) GetAuthSources() []ParamAuthSource {
	return p.AuthSources
}

// NewBooleanParameter is a convenience function for initializing a BooleanParameter.
func NewBooleanParameter(name, desc string) *BooleanParameter {
	return &BooleanParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeBool,
			Desc:        desc,
			AuthSources: nil,
		},
	}
}

// NewBooleanParameterWithAuth is a convenience function for initializing a BooleanParameter with a list of ParamAuthSource.
func NewBooleanParameterWithAuth(name, desc string, authSources []ParamAuthSource) *BooleanParameter {
	return &BooleanParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeBool,
			Desc:        desc,
			AuthSources: authSources,
		},
	}
}

var _ Parameter = &BooleanParameter{}

// BooleanParameter is a parameter representing the "boolean" type.
type BooleanParameter struct {
	CommonParameter `yaml:",inline"`
}

func (p *BooleanParameter) Parse(v any) (any, error) {
	newV, ok := v.(bool)
	if !ok {
		return nil, &ParseTypeError{p.Name, p.Type, v}
	}
	return newV, nil
}

func (p *BooleanParameter) GetAuthSources() []ParamAuthSource {
	return p.AuthSources
}

// NewArrayParameter is a convenience function for initializing a ArrayParameter.
func NewArrayParameter(name, desc string, items Parameter) *ArrayParameter {
	return &ArrayParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeArray,
			Desc:        desc,
			AuthSources: nil,
		},
		Items: items,
	}
}

// NewArrayParameterWithAuth is a convenience function for initializing a ArrayParameter with a list of ParamAuthSource.
func NewArrayParameterWithAuth(name, desc string, items Parameter, authSources []ParamAuthSource) *ArrayParameter {
	return &ArrayParameter{
		CommonParameter: CommonParameter{
			Name:        name,
			Type:        typeArray,
			Desc:        desc,
			AuthSources: authSources,
		},
		Items: items,
	}
}

var _ Parameter = &ArrayParameter{}

// ArrayParameter is a parameter representing the "array" type.
type ArrayParameter struct {
	CommonParameter `yaml:",inline"`
	Items           Parameter `yaml:"items"`
}

func (p *ArrayParameter) UnmarshalYAML(unmarshal func(interface{}) error) error {
	if err := unmarshal(&p.CommonParameter); err != nil {
		return err
	}
	var rawItem struct {
		Items util.DelayedUnmarshaler `yaml:"items"`
	}
	if err := unmarshal(&rawItem); err != nil {
		return err
	}
	i, err := parseParamFromDelayedUnmarshaler(&rawItem.Items)
	if err != nil {
		return fmt.Errorf("unable to parse 'items' field: %w", err)
	}
	if i.GetAuthSources() != nil {
		return fmt.Errorf("nested items should not have auth sources.")
	}
	p.Items = i

	return nil
}

func (p *ArrayParameter) Parse(v any) (any, error) {
	arrVal, ok := v.([]any)
	if !ok {
		return nil, &ParseTypeError{p.Name, p.Type, arrVal}
	}
	rtn := make([]any, 0, len(arrVal))
	for idx, val := range arrVal {
		val, err := p.Items.Parse(val)
		if err != nil {
			return nil, fmt.Errorf("unable to parse element #%d: %w", idx, err)
		}
		rtn = append(rtn, val)
	}
	return rtn, nil
}

func (p *ArrayParameter) GetAuthSources() []ParamAuthSource {
	return p.AuthSources
}