// Copyright (C) 2025 wangyusong
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

package rewrite

import (
	"context"
	"html/template"
	"regexp"
	"strings"
	"unicode/utf8"

	"github.com/pkg/errors"
	"k8s.io/utils/ptr"

	"github.com/glidea/zenfeed/pkg/component"
	"github.com/glidea/zenfeed/pkg/config"
	"github.com/glidea/zenfeed/pkg/llm"
	"github.com/glidea/zenfeed/pkg/llm/prompt"
	"github.com/glidea/zenfeed/pkg/model"
	"github.com/glidea/zenfeed/pkg/telemetry"
	telemetrymodel "github.com/glidea/zenfeed/pkg/telemetry/model"
	"github.com/glidea/zenfeed/pkg/util/buffer"
	"github.com/glidea/zenfeed/pkg/util/crawl"
)

// --- Interface code block ---
type Rewriter interface {
	component.Component
	config.Watcher

	// Labels applies rewrite rules to the given labels and returns the modified labels.
	// Note: this method modifies the input labels in place.
	// If a rule's action is ActionDropFeed, it returns nil to indicate the item should be dropped.
	Labels(ctx context.Context, labels model.Labels) (model.Labels, error)
}

type Config []Rule

func (c *Config) Validate() error {
	for i := range *c {
		if err := (*c)[i].Validate(); err != nil {
			return errors.Wrapf(err, "validate and adjust rewrite config")
		}
	}

	return nil
}

func (c *Config) From(app *config.App) {
	for _, r := range app.Storage.Feed.Rewrites {
		var rc Rule
		rc.From(&r)
		*c = append(*c, rc)
	}
}

type Dependencies struct {
	LLMFactory llm.Factory
}

type Rule struct {
	// If is the condition to check before applying the rule.
	// If not set, the rule will be applied.
	If  []string
	if_ model.LabelFilters

	// SourceLabel specifies which label's value to use as source text.
	// Default is model.LabelContent.
	SourceLabel string

	// SkipTooShortThreshold is the threshold of the source text length.
	// If the source text is shorter than this threshold, it will be skipped.
	SkipTooShortThreshold *int

	// Transform used to transform the source text.
	// If not set, transform to original source text.
	Transform *Transform

	// Match used to match the text after transform.
	// If not set, match all.
	Match   string
	matchRE *regexp.Regexp

	// Action determines what to do if matchs.
	Action Action

	// Label is the label to create or update.
	Label string
}

func (r *Rule) Validate() error { //nolint:cyclop,gocognit,funlen
	// If.
	if len(r.If) > 0 {
		if_, err := model.NewLabelFilters(r.If)
		if err != nil {
			return errors.Wrapf(err, "invalid if %q", r.If)
		}
		r.if_ = if_
	}

	// Source label.
	if r.SourceLabel == "" {
		r.SourceLabel = model.LabelContent
	}
	if r.SkipTooShortThreshold == nil {
		r.SkipTooShortThreshold = ptr.To(0)
	}

	// Transform.
	if r.Transform != nil {
		if r.Transform.ToText == nil {
			return errors.New("to_text is required when transform is set")
		}

		switch r.Transform.ToText.Type {
		case ToTextTypePrompt:
			if r.Transform.ToText.Prompt == "" {
				return errors.New("to text prompt is required for prompt type")
			}
			tmpl, err := template.New("").Parse(r.Transform.ToText.Prompt)
			if err != nil {
				return errors.Wrapf(err, "parse prompt template %s", r.Transform.ToText.Prompt)
			}

			buf := buffer.Get()
			defer buffer.Put(buf)
			if err := tmpl.Execute(buf, prompt.Builtin); err != nil {
				return errors.Wrapf(err, "execute prompt template %s", r.Transform.ToText.Prompt)
			}
			r.Transform.ToText.promptRendered = buf.String()

		case ToTextTypeCrawl, ToTextTypeCrawlByJina:
			// No specific validation for crawl type here, as the source text itself is the URL.
		default:
			return errors.Errorf("unknown transform type: %s", r.Transform.ToText.Type)
		}
	}

	// Match.
	if r.Match == "" {
		r.Match = ".*"
	}
	re, err := regexp.Compile(r.Match)
	if err != nil {
		return errors.Wrapf(err, "compile match regex %s", r.Match)
	}
	r.matchRE = re

	// Action.
	switch r.Action {
	case "":
		r.Action = ActionCreateOrUpdateLabel
	case ActionCreateOrUpdateLabel:
		if r.Label == "" {
			return errors.New("label is required for create or update label action")
		}
	case ActionDropFeed:
	default:
		return errors.Errorf("invalid action: %s", r.Action)
	}

	return nil
}

func (r *Rule) From(c *config.RewriteRule) {
	r.If = c.If
	r.SourceLabel = c.SourceLabel
	r.SkipTooShortThreshold = c.SkipTooShortThreshold
	if c.Transform != nil {
		t := &Transform{}
		if c.Transform.ToText != nil {
			toText := &ToText{
				LLM:    c.Transform.ToText.LLM,
				Prompt: c.Transform.ToText.Prompt,
			}
			toText.Type = ToTextType(c.Transform.ToText.Type)
			if toText.Type == "" {
				toText.Type = ToTextTypePrompt // Default to prompt if not specified.
			}
			t.ToText = toText
		}
		r.Transform = t
	}
	r.Match = c.Match
	if r.Match == "" {
		r.Match = c.MatchRE
	}
	r.Action = Action(c.Action)
	r.Label = c.Label
}

type Transform struct {
	ToText *ToText
}

type ToText struct {
	Type ToTextType

	// LLM is the name of the LLM to use.
	// Only used when Type is ToTextTypePrompt.
	LLM string

	// Prompt is the prompt for LLM completion.
	// The source text will automatically be injected into the prompt.
	// Only used when Type is ToTextTypePrompt.
	Prompt         string
	promptRendered string
}

type ToTextType string

const (
	ToTextTypePrompt      ToTextType = "prompt"
	ToTextTypeCrawl       ToTextType = "crawl"
	ToTextTypeCrawlByJina ToTextType = "crawl_by_jina"
)

type Action string

const (
	ActionDropFeed            Action = "drop_feed"
	ActionCreateOrUpdateLabel Action = "create_or_update_label"
)

// --- Factory code block ---
type Factory component.Factory[Rewriter, config.App, Dependencies]

func NewFactory(mockOn ...component.MockOption) Factory {
	if len(mockOn) > 0 {
		return component.FactoryFunc[Rewriter, config.App, Dependencies](func(instance string, app *config.App, dependencies Dependencies) (Rewriter, error) {
			m := &mockRewriter{}
			component.MockOptions(mockOn).Apply(&m.Mock)

			return m, nil
		})
	}

	return component.FactoryFunc[Rewriter, config.App, Dependencies](new)
}

func new(instance string, app *config.App, dependencies Dependencies) (Rewriter, error) {
	c := &Config{}
	c.From(app)
	if err := c.Validate(); err != nil {
		return nil, errors.Wrap(err, "validate and adjust rewrite config")
	}

	return &rewriter{
		Base: component.New(&component.BaseConfig[Config, Dependencies]{
			Name:         "Rewriter",
			Instance:     instance,
			Config:       c,
			Dependencies: dependencies,
		}),
		crawler:     crawl.NewLocal(),
		jinaCrawler: crawl.NewJina(app.Jina.Token),
	}, nil
}

// --- Implementation code block ---

type rewriter struct {
	*component.Base[Config, Dependencies]

	crawler     crawl.Crawler
	jinaCrawler crawl.Crawler
}

func (r *rewriter) Reload(app *config.App) error {
	newConfig := &Config{}
	newConfig.From(app)
	if err := newConfig.Validate(); err != nil {
		return errors.Wrap(err, "validate and adjust rewrite config")
	}
	r.SetConfig(newConfig)

	r.jinaCrawler = crawl.NewJina(app.Jina.Token)

	return nil
}

func (r *rewriter) Labels(ctx context.Context, labels model.Labels) (rewritten model.Labels, err error) {
	ctx = telemetry.StartWith(ctx, append(r.TelemetryLabels(), telemetrymodel.KeyOperation, "Labels")...)
	defer func() { telemetry.End(ctx, err) }()

	rules := *r.Config()
	for _, rule := range rules {
		// If.
		if !rule.if_.Match(labels) {
			continue
		}

		// Get source text based on source label.
		sourceText := labels.Get(rule.SourceLabel)
		if utf8.RuneCountInString(sourceText) < *rule.SkipTooShortThreshold {
			continue
		}

		// Transform text if configured.
		text := sourceText
		if rule.Transform != nil && rule.Transform.ToText != nil {
			transformed, err := r.transformText(ctx, rule.Transform, sourceText)
			if err != nil {
				return nil, errors.Wrap(err, "transform text")
			}
			text = transformed
		}

		// Check if text matches the rule.
		if !rule.matchRE.MatchString(text) {
			continue
		}

		// Handle actions.
		switch rule.Action {
		case ActionDropFeed:
			return nil, nil
		case ActionCreateOrUpdateLabel:
			labels.Put(rule.Label, text, false)
		}
	}

	labels.EnsureSorted()

	return labels, nil
}

// transformText transforms text using configured LLM or by crawling a URL.
func (r *rewriter) transformText(ctx context.Context, transform *Transform, text string) (string, error) {
	switch transform.ToText.Type {
	case ToTextTypeCrawl:
		return r.transformTextCrawl(ctx, r.crawler, text)
	case ToTextTypeCrawlByJina:
		return r.transformTextCrawl(ctx, r.jinaCrawler, text)

	case ToTextTypePrompt:
		return r.transformTextPrompt(ctx, transform, text)
	default:
		return r.transformTextPrompt(ctx, transform, text)
	}
}

func (r *rewriter) transformTextCrawl(ctx context.Context, crawler crawl.Crawler, url string) (string, error) {
	mdBytes, err := crawler.Markdown(ctx, url)
	if err != nil {
		return "", errors.Wrapf(err, "crawl %s", url)
	}

	return string(mdBytes), nil
}

// transformTextPrompt transforms text using configured LLM.
func (r *rewriter) transformTextPrompt(ctx context.Context, transform *Transform, text string) (string, error) {
	// Get LLM instance.
	llm := r.Dependencies().LLMFactory.Get(transform.ToText.LLM)

	// Call completion.
	result, err := llm.String(ctx, []string{
		transform.ToText.promptRendered,
		text, // TODO: may place to first line to hit the model cache in different rewrite rules.
	})
	if err != nil {
		return "", errors.Wrap(err, "llm completion")
	}

	return r.transformTextHack(result), nil
}

func (r *rewriter) transformTextHack(text string) string {
	// TODO: optimize this.
	text = strings.ReplaceAll(text, "```html", "")
	text = strings.ReplaceAll(text, "```markdown", "")
	text = strings.ReplaceAll(text, "```", "")

	return text
}

type mockRewriter struct {
	component.Mock
}

func (r *mockRewriter) Reload(app *config.App) error {
	args := r.Called(app)

	return args.Error(0)
}

func (r *mockRewriter) Labels(ctx context.Context, labels model.Labels) (model.Labels, error) {
	args := r.Called(ctx, labels)
	if args.Get(0) == nil {
		return nil, args.Error(1)
	}

	return args.Get(0).(model.Labels), args.Error(1)
}