import { Injectable, Logger, OnModuleInit } from '@nestjs/common';
import { copyFileSync, existsSync, mkdirSync, readFileSync, writeFileSync } from 'fs';
import { dirname, join } from 'path';
import {
    AI_ACTOR_KEYS,
    AI_ENV_SEEDS,
    DEFAULT_AI_CONFIG,
    DEFAULT_AI_PROMPTS,
    type AiActorKey,
    type AiConfig,
    type AiPromptConfig,
    type AiProvider,
} from './ai.defaults';

const CONFIG_PATH = join(process.cwd(), 'data', 'ai.json');
const BACKUP_DIR = join(process.cwd(), 'data', 'ai-backups');

// File-backed AI config — provider, model, temperature, and per-actor
// system prompt templates. API keys stay in env. Mirrors
// TelephonyConfigService.
@Injectable()
export class AiConfigService implements OnModuleInit {
    private readonly logger = new Logger(AiConfigService.name);
    private cached: AiConfig | null = null;

    onModuleInit() {
        this.ensureReady();
    }

    getConfig(): AiConfig {
        if (this.cached) return this.cached;
        return this.load();
    }

    updateConfig(updates: Partial<AiConfig>): AiConfig {
        const current = this.getConfig();
        const merged: AiConfig = {
            ...current,
            ...updates,
            // Clamp temperature to a sane range so an admin typo can't break
            // the model — most providers reject < 0 or > 2.
            temperature:
                updates.temperature !== undefined
                    ? Math.max(0, Math.min(2, updates.temperature))
                    : current.temperature,
            version: (current.version ?? 0) + 1,
            updatedAt: new Date().toISOString(),
        };
        this.backup();
        this.writeFile(merged);
        this.cached = merged;
        this.logger.log(`AI config updated to v${merged.version}`);
        return merged;
    }

    resetConfig(): AiConfig {
        this.backup();
        const fresh = JSON.parse(JSON.stringify(DEFAULT_AI_CONFIG)) as AiConfig;
        this.writeFile(fresh);
        this.cached = fresh;
        this.logger.log('AI config reset to defaults');
        return fresh;
    }

    // Update a single actor's prompt template, preserving the audit
    // trail. Used by the wizard's edit slideout. Validates the actor
    // key so a typo from a hand-crafted PUT can't write garbage.
    updatePrompt(actor: AiActorKey, template: string, editedBy: string | null): AiConfig {
        if (!AI_ACTOR_KEYS.includes(actor)) {
            throw new Error(`Unknown AI actor: ${actor}`);
        }
        const current = this.getConfig();
        const existing = current.prompts[actor] ?? DEFAULT_AI_PROMPTS[actor];
        const updatedPrompt: AiPromptConfig = {
            ...existing,
            template,
            lastEditedAt: new Date().toISOString(),
            lastEditedBy: editedBy,
        };
        const merged: AiConfig = {
            ...current,
            prompts: { ...current.prompts, [actor]: updatedPrompt },
            version: (current.version ?? 0) + 1,
            updatedAt: new Date().toISOString(),
        };
        this.backup();
        this.writeFile(merged);
        this.cached = merged;
        this.logger.log(`AI prompt for actor '${actor}' updated to v${merged.version}`);
        return merged;
    }

    // Restore a single actor's prompt back to the SDK-shipped default.
    // Clears the audit fields so it looks "fresh" in the UI.
    resetPrompt(actor: AiActorKey): AiConfig {
        if (!AI_ACTOR_KEYS.includes(actor)) {
            throw new Error(`Unknown AI actor: ${actor}`);
        }
        const current = this.getConfig();
        const fresh: AiPromptConfig = {
            ...DEFAULT_AI_PROMPTS[actor],
            lastEditedAt: null,
            lastEditedBy: null,
        };
        const merged: AiConfig = {
            ...current,
            prompts: { ...current.prompts, [actor]: fresh },
            version: (current.version ?? 0) + 1,
            updatedAt: new Date().toISOString(),
        };
        this.backup();
        this.writeFile(merged);
        this.cached = merged;
        this.logger.log(`AI prompt for actor '${actor}' reset to default`);
        return merged;
    }

    // Render a prompt with `{{variable}}` substitution. Variables not
    // present in `vars` are left as-is so a missing fill is loud
    // (the AI sees `{{leadName}}` literally) rather than silently
    // dropping the placeholder. Falls back to DEFAULT_AI_PROMPTS if
    // the actor key is missing from the loaded config (handles old
    // ai.json files that predate this refactor).
    renderPrompt(actor: AiActorKey, vars: Record<string, string | number | null | undefined>): string {
        const cfg = this.getConfig();
        const prompt = cfg.prompts?.[actor] ?? DEFAULT_AI_PROMPTS[actor];
        const template = prompt.template;
        return template.replace(/\{\{(\w+)\}\}/g, (match, key) => {
            const value = vars[key];
            if (value === undefined || value === null) return match;
            return String(value);
        });
    }

    private ensureReady(): AiConfig {
        if (existsSync(CONFIG_PATH)) {
            return this.load();
        }
        const seeded: AiConfig = JSON.parse(JSON.stringify(DEFAULT_AI_CONFIG)) as AiConfig;
        let appliedCount = 0;
        for (const seed of AI_ENV_SEEDS) {
            const value = process.env[seed.env];
            if (value === undefined || value === '') continue;
            (seeded as any)[seed.field] = value;
            appliedCount += 1;
        }
        seeded.version = 1;
        seeded.updatedAt = new Date().toISOString();
        this.writeFile(seeded);
        this.cached = seeded;
        this.logger.log(
            `AI config seeded from env (${appliedCount} env var${appliedCount === 1 ? '' : 's'} applied)`,
        );
        return seeded;
    }

    private load(): AiConfig {
        try {
            const raw = readFileSync(CONFIG_PATH, 'utf8');
            const parsed = JSON.parse(raw);
            // Merge incoming prompts against defaults so old ai.json
            // files (written before the prompts refactor) get topped
            // up with the new actor entries instead of crashing on
            // first read. Per-actor merging keeps any admin edits
            // intact while filling in missing actors.
            const mergedPrompts: Record<AiActorKey, AiPromptConfig> = { ...DEFAULT_AI_PROMPTS };
            if (parsed.prompts && typeof parsed.prompts === 'object') {
                for (const key of AI_ACTOR_KEYS) {
                    const incoming = parsed.prompts[key];
                    if (incoming && typeof incoming === 'object') {
                        mergedPrompts[key] = {
                            ...DEFAULT_AI_PROMPTS[key],
                            ...incoming,
                            // Always pull `defaultTemplate` from the
                            // shipped defaults — never trust the
                            // file's copy, since the SDK baseline can
                            // change between releases and we want
                            // "reset to default" to always reset to
                            // the latest baseline.
                            defaultTemplate: DEFAULT_AI_PROMPTS[key].defaultTemplate,
                        };
                    }
                }
            }
            const merged: AiConfig = {
                ...DEFAULT_AI_CONFIG,
                ...parsed,
                provider: (parsed.provider ?? DEFAULT_AI_CONFIG.provider) as AiProvider,
                prompts: mergedPrompts,
            };
            this.cached = merged;
            this.logger.log('AI config loaded from file');
            return merged;
        } catch (err) {
            this.logger.warn(`Failed to load AI config, using defaults: ${err}`);
            const fresh = JSON.parse(JSON.stringify(DEFAULT_AI_CONFIG)) as AiConfig;
            this.cached = fresh;
            return fresh;
        }
    }

    private writeFile(cfg: AiConfig) {
        const dir = dirname(CONFIG_PATH);
        if (!existsSync(dir)) mkdirSync(dir, { recursive: true });
        writeFileSync(CONFIG_PATH, JSON.stringify(cfg, null, 2), 'utf8');
    }

    private backup() {
        try {
            if (!existsSync(CONFIG_PATH)) return;
            if (!existsSync(BACKUP_DIR)) mkdirSync(BACKUP_DIR, { recursive: true });
            const ts = new Date().toISOString().replace(/[:.]/g, '-');
            copyFileSync(CONFIG_PATH, join(BACKUP_DIR, `ai-${ts}.json`));
        } catch (err) {
            this.logger.warn(`AI config backup failed: ${err}`);
        }
    }
}