import { createCerebras } from "@ai-sdk/cerebras"

import type { StageConfig } from "../config"
import type { ChangedFile, GitClient } from "../git"
import { buildDominantTokenRetryHint, selectBestCommitSubject } from "./candidate-ranking"
import { buildCommitContext, type CommitContextStats } from "./context-builder"
import { generateCommitDraft } from "./draft"
import { resolveTokenizer } from "./tokenizer"

type GenerateAiCommitSummaryParams = {
  git: GitClient
  files: ChangedFile[]
  selectedPaths: string[]
  aiConfig: StageConfig["ai"]
  onContextBuilt?: (stats: CommitContextStats) => void
}

export async function generateAiCommitSummary({
  git,
  files,
  selectedPaths,
  aiConfig,
  onContextBuilt,
}: GenerateAiCommitSummaryParams): Promise<string> {
  if (!aiConfig.enabled) {
    throw new Error("AI commit generation is disabled in config.")
  }
  if (aiConfig.provider !== "cerebras") {
    throw new Error(`Unsupported AI provider: ${aiConfig.provider}`)
  }
  if (!aiConfig.apiKey.trim()) {
    throw new Error("AI commit generation requires ai.api_key.")
  }

  const selected = selectedPaths.map((path) => path.trim()).filter(Boolean)
  if (selected.length === 0) {
    throw new Error("No files selected for AI commit.")
  }

  const tokenizer = resolveTokenizer(aiConfig.model)
  const fileByPath = new Map(files.map((file) => [file.path, file]))
  const { context, stats } = await buildCommitContext({
    git,
    fileByPath,
    selectedPaths: selected,
    maxInputTokens: aiConfig.maxInputTokens,
    tokenizer,
  })
  onContextBuilt?.(stats)

  const cerebras = createCerebras({
    apiKey: aiConfig.apiKey,
  })
  const model = cerebras(aiConfig.model)

  const firstCandidate = await generateCommitDraft(model, context, aiConfig.reasoningEffort, false)
  if (firstCandidate) {
    const firstEvaluation = selectBestCommitSubject({
      candidates: [firstCandidate],
      context,
      selectedPaths: selected,
    })
    if (firstEvaluation && !firstEvaluation.hardRejected && firstEvaluation.score >= FAST_ACCEPT_SCORE) {
      return firstEvaluation.subject
    }
  }

  const candidates: string[] = firstCandidate ? [firstCandidate] : []
  const retryReason = firstCandidate
    ? buildDominantTokenRetryHint({
        context,
        selectedPaths: selected,
        subject: firstCandidate,
      }) ?? DEFAULT_RETRY_REASON
    : DEFAULT_RETRY_REASON
  const secondCandidate = await generateCommitDraft(
    model,
    context,
    aiConfig.reasoningEffort,
    true,
    retryReason,
  )
  if (secondCandidate) {
    candidates.push(secondCandidate)
  }

  const best = selectBestCommitSubject({
    candidates,
    context,
    selectedPaths: selected,
  })
  if (best) {
    return best.subject
  }

  throw new Error(
    "AI did not return a usable conventional commit message. Try again or adjust ai.reasoning_effort / ai.max_input_tokens.",
  )
}

const FAST_ACCEPT_SCORE = 40
const DEFAULT_RETRY_REASON = "cover dominant changed themes across modules when applicable"