package main

import (
    "fmt"
    "strings"

    "github.com/mattermost/mattermost/server/public/model"
    "github.com/mattermost/mattermost/server/public/plugin"
)

const botUsername = "matty"
const botDisplayName = "Matty AI"
const botDescription = "AI chat agent powered by Ollama."

// OnActivate is invoked when the plugin is activated.
func (p *Plugin) OnActivate() error {
    // Register the /ai slash command.
    if err := p.API.RegisterCommand(&model.Command{
        Trigger:          "ai",
        DisplayName:      "Matty",
        Description:      "AI chat powered by Ollama. @matty",
        AutoComplete:     true,
        AutoCompleteDesc: "Chat with the AI. Usage: /ai <prompt>",
        AutoCompleteHint: "<prompt>",
    }); err != nil {
        return fmt.Errorf("register command: %w", err)
    }



    // Ensure the bot account exists — create or re-use.
    var err error
    p.botUserID, err = p.ensureBot()
    if err != nil {
        return fmt.Errorf("bot setup: %w", err)
    }

    // Initialise components.
    cfg := p.getConfiguration()
    if cfg == nil {
        // Load configuration first.
        if err := p.OnConfigurationChange(); err != nil {
            return fmt.Errorf("initial configuration: %w", err)
        }
        cfg = p.getConfiguration()
    }

    p.ollamaClient = NewOllamaClient(cfg.OllamaURL, p.API.LogInfo)
    p.conversationStore = NewConversationStore(p.API)
    p.rateLimiter = NewRateLimiter(cfg.RateLimitPerMinute)
    p.engagementEngine = NewEngagementEngine()

    return nil
}

// ensureBot finds or creates the bot account and returns its user ID.
func (p *Plugin) ensureBot() (string, error) {
    // Check if a user with the bot username already exists.
    user, appErr := p.API.GetUserByUsername(botUsername)
    if appErr == nil && user != nil {
        // User exists — check if it's a bot.
        if _, botErr := p.API.GetBot(user.Id, true); botErr == nil {
            return user.Id, nil
        }
        // User exists but is not a bot — create the bot association.
        createdBot, createErr := p.API.CreateBot(&model.Bot{
            Username:    botUsername,
            DisplayName: botDisplayName,
            Description: botDescription,
        })
        if createErr != nil {
            return "", fmt.Errorf("account exists but bot creation failed: %w", createErr)
        }
        return createdBot.UserId, nil
    }

    // No existing user — create bot fresh.
    createdBot, appErr := p.API.CreateBot(&model.Bot{
        Username:    botUsername,
        DisplayName: botDisplayName,
        Description: botDescription,
    })
    if appErr != nil {
        return "", fmt.Errorf("create bot: %w", appErr)
    }
    return createdBot.UserId, nil
}

// OnDeactivate is invoked when the plugin is deactivated.
func (p *Plugin) OnDeactivate() error {
    // The bot account persists across restarts — it will be re-used
    // on next OnActivate. No explicit cleanup needed.
    return nil
}

// Implemented returns the list of hooks this plugin handles.
func (p *Plugin) Implemented() ([]string, error) {
    return []string{
        "OnActivate",
        "OnDeactivate",
        "OnConfigurationChange",
        "ExecuteCommand",
        "MessageHasBeenPosted",
    }, nil
}

// MessageHasBeenPosted is the primary entry point for @-mention interaction.
func (p *Plugin) MessageHasBeenPosted(c *plugin.Context, post *model.Post) {
    // Never respond to our own posts.
    if post.UserId == p.botUserID {
        return
    }

    // Never respond to other bots.
    if post.IsFromOAuthBot() {
        return
    }

    cfg := p.getConfiguration()

    // Check if the bot is @-mentioned in the message.
    mentioned := strings.Contains(
        strings.ToLower(post.Message),
        "@"+botUsername,
    )

    isActive := p.engagementEngine.IsActive(post.UserId, post.ChannelId)

    // If not mentioned and not in an active conversation, ignore.
    if !mentioned && !isActive {
        return
    }

    // Build the prompt.
    prompt := post.Message
    if mentioned {
        prompt = strings.TrimSpace(strings.Replace(
            strings.ToLower(prompt),
            "@"+botUsername,
            "",
            1,
        ))
    }

    // Handle stop words before sending to Ollama.
    if stopWordMatch(prompt, cfg.stopWordSet()) {
        p.engagementEngine.Sleep(post.UserId, post.ChannelId)
        p.postReply(post, "Goodbye! _Matty_ signing off. :wave:")
        return
    }

    // Authorisation check.
    if users := cfg.allowedUsers(); users != nil && !users[post.UserId] {
        p.postReply(post, "You are not authorised to use this bot.")
        return
    }

    // Rate limit check.
    if !p.rateLimiter.Allow(post.UserId) {
        p.postReply(post, "Rate limit exceeded. Please wait before sending another request.")
        return
    }

    // Wake or refresh the engagement session.
    // Fresh @-mention resets conversation history so old context doesn't bleed.
    if mentioned {
        _ = p.conversationStore.Reset(post.UserId, post.ChannelId)
        p.engagementEngine.Wake(post.UserId, post.ChannelId)
    }

    // Build conversation context.
    messages, err := p.conversationStore.BuildMessages(post.UserId, post.ChannelId, prompt)
    if err != nil {
        p.postReply(post, "Failed to build conversation context.")
        return
    }

    // Limit conversation history based on brevity — fewer sentences = less context
    // to prevent the model re-addressing old messages.
    if cfg.Brevity != "" && cfg.Brevity != "0" {
        brevity := 0
        fmt.Sscanf(cfg.Brevity, "%d", &brevity)
        if brevity > 0 && len(messages) > 2 {
            // Keep: system prompt (added later) + (brevity * 2) lines of history + current prompt
            keep := brevity * 2
            if keep < 2 {
                keep = 2 // always keep at least the current exchange
            }
            if keep < len(messages) {
                messages = messages[len(messages)-keep:]
            }
        }
    }

    // Prepend the persona system prompt to set the bot's character.
    // Priority: KV override > dropdown selection
    //   If dropdown = "custom" → use CustomPersona textarea field
    //   Otherwise → resolve from personaLibrary
    persona := p.GetPersonaOverride(post.UserId, post.ChannelId)
    persona = resolvePersona(persona)
    if persona == "" {
        if cfg.Persona == "custom" {
            persona = cfg.CustomPersona
        } else {
            persona = resolvePersona(cfg.Persona)
            // If resolvePersona returned empty but a value was set, use it as-is (legacy fallback).
            if persona == "" && cfg.Persona != "" {
                persona = cfg.Persona
            }
        }
    }
    systemPrompt := ""
    if persona != "" {
        systemPrompt = "You are " + persona + ". Respond in character. Only respond to the latest message — do not re-address earlier messages. Vary your openings and phrasing each time."
        if cfg.Brevity != "" && cfg.Brevity != "0" {
            systemPrompt += " Reply in " + cfg.Brevity + " sentences or fewer."
        }
        messages = append([]ChatMessage{{
            Role:    "system",
            Content: systemPrompt,
        }}, messages...)
    }

    // Calculate the resolved token cap.
    maxTokens := cfg.MaxTokens
    if cfg.Brevity != "" && cfg.Brevity != "0" {
        brevity := 0
        fmt.Sscanf(cfg.Brevity, "%d", &brevity)
        if brevity > 0 {
            suggested := 100 + brevity*75
            if maxTokens == 0 || suggested < maxTokens {
                maxTokens = suggested
            }
        }
    }

    if cfg.DebugLogging {
        p.API.LogInfo("Chat request",
            "model", cfg.DefaultModel,
            "ollama_url", cfg.OllamaURL,
            "persona", cfg.Persona,
            "custom_persona", cfg.CustomPersona,
            "brevity", cfg.Brevity,
            "max_tokens_config", cfg.MaxTokens,
            "max_tokens_resolved", maxTokens,
            "repeat", cfg.RepeatPenalty,
            "freq", cfg.FrequencyPenalty,
            "rate_limit", cfg.RateLimitPerMinute,
            "allowed_users", cfg.AllowedUserIDs,
            "stop_words", cfg.StopWords,
            "system", systemPrompt)
    }

    // Stream the full response from Ollama, then post once.
    opts := map[string]any{}
    if maxTokens > 0 {
        opts["num_predict"] = maxTokens
    }
    if cfg.RepeatPenalty > 0 {
        opts["repeat_penalty"] = float64(cfg.RepeatPenalty) / 10.0
    }
    if cfg.FrequencyPenalty > 0 {
        opts["frequency_penalty"] = float64(cfg.FrequencyPenalty) / 10.0
    }
    stream, err := p.ollamaClient.ChatCompletionStream(&ChatRequest{
        Model:    cfg.DefaultModel,
        Messages: messages,
        Options:  opts,
    })
    if err != nil {
        p.postReply(post, "Matty is asleep. @matty when you need me.")
        return
    }

    var fullResponse strings.Builder
    for event := range stream {
        if event.Error != nil {
            p.API.LogError("Stream error", "error", event.Error.Error())
            fullResponse.WriteString("\n\n(Matty is asleep. @matty when you need me.)")
            break
        }
        fullResponse.WriteString(event.Token)
        if event.Done {
            break
        }
    }

    p.postReply(post, fullResponse.String())
}

// postReply creates a direct channel post.
func (p *Plugin) postReply(replyTo *model.Post, text string) {
    replyPost := &model.Post{
        UserId:    p.botUserID,
        ChannelId: replyTo.ChannelId,
        Message:   text,
    }

    if _, appErr := p.API.CreatePost(replyPost); appErr != nil {
        // Log the failure but don't crash.
        p.API.LogError("Failed to create reply post", "error", appErr.Error())
    }
}