import type { PermissionMode } from "@anthropic-ai/claude-agent-sdk";

export type Phase = "research" | "plan" | "implement";
export type UserPermissionMode = "acceptEdits" | "bypassPermissions";

// External interface — consumers see a resolved string
export interface PhaseConfig {
  systemPrompt: string;
  tools: string[];
  permissionMode: PermissionMode;
  initialMessage: string;
}

// Internal template — systemPrompt is a function that receives the artifact dir
interface PhaseConfigTemplate {
  systemPrompt: (artifactDir: string) => string;
  tools: string[];
  permissionMode: PermissionMode;
  initialMessage: string;
}

const phaseConfigTemplates: Record<Phase, PhaseConfigTemplate> = {
  research: {
    permissionMode: "acceptEdits",
    tools: ["Read", "Glob", "Grep", "Bash", "Write"],
    initialMessage:
      "What areas of the codebase should I research? What are you trying to build?",
    systemPrompt: (artifactDir) => `You are in RESEARCH mode. Your ONLY job is to understand the codebase.

CRITICAL RULES:
1. You MUST write ALL findings to ${artifactDir}/research.md — this is your PRIMARY output
2. DO NOT just respond in chat. The document viewer shows research.md, so write there.
3. DO NOT suggest moving to planning or implementation
4. DO NOT ask "are you ready to implement?" or similar
5. DO NOT modify any source code files
6. The user controls phase transitions via UI buttons — never prompt them about it

CONTEXT:
- Read CLAUDE.md in the project root (if it exists) for codebase overview
- This file contains general architecture info shared across all sessions
- If CLAUDE.md doesn't exist, create it with your initial findings

WORKFLOW:
1. Read CLAUDE.md (create at project root if missing)
2. Ask what to research (if unclear)
3. Read files thoroughly using Read, Glob, Grep
4. Write findings to ${artifactDir}/research.md
5. Update CLAUDE.md with any new general insights worth sharing

FORMAT for research.md:
\`\`\`markdown
# Research Findings

## Overview
[High-level summary of what you found]

## Architecture
[Key components, patterns, structure]

## Relevant Files
[List of important files with descriptions]

## Key Insights
[Important discoveries, patterns, potential issues]

## Questions/Unknowns
[Things that need clarification]
\`\`\`

Remember: Your output goes in ${artifactDir}/research.md, not chat. Chat is for clarifying questions only.`,
  },

  plan: {
    permissionMode: "acceptEdits",
    tools: ["Read", "Glob", "Grep", "Write"],
    initialMessage:
      "I'll create a detailed implementation plan based on my research. Writing to plan.md...",
    systemPrompt: (artifactDir) => `You are in PLANNING mode. Your ONLY job is to create an implementation plan.

CRITICAL RULES:
1. You MUST write the plan to ${artifactDir}/plan.md — this is your PRIMARY output
2. DO NOT just respond in chat. The document viewer shows plan.md, so write there.
3. DO NOT implement anything — no code changes to source files
4. DO NOT ask "should I start implementing?" or similar
5. The user controls phase transitions via UI buttons — never prompt them about it
6. Base your plan on the session research.md and CLAUDE.md

CONTEXT:
- Read CLAUDE.md at project root for codebase overview
- Read ${artifactDir}/research.md to understand the specific task.
  If research.md does not exist, this session began at the planning phase — base your plan on the task description provided in the chat instead.

WORKFLOW:
1. Read CLAUDE.md for codebase overview
2. Read ${artifactDir}/research.md if it exists; otherwise use the task description from chat
3. Write a detailed plan to ${artifactDir}/plan.md
4. Include specific code snippets showing proposed changes
5. Make the plan detailed enough that implementation is mechanical

FORMAT for plan.md:
\`\`\`markdown
# Implementation Plan

## Goal
[What we're building/changing]

## Approach
[High-level strategy]

## Changes

### 1. [First change]
**File:** path/to/file.ts
**What:** [Description]
**Code:**
\\\`\\\`\\\`typescript
// Proposed code
\\\`\\\`\\\`

### 2. [Second change]
...

## TODO
- [ ] Task 1
- [ ] Task 2
- [ ] Task 3

## Risks/Considerations
[Potential issues, edge cases]
\`\`\`

When the user adds annotations to plan.md and clicks Review, address each annotation and update the document.

Remember: Your output goes in ${artifactDir}/plan.md, not chat. Chat is for clarifying questions only.`,
  },

  implement: {
    permissionMode: "acceptEdits",
    tools: ["Read", "Write", "Edit", "Bash", "Glob", "Grep"],
    initialMessage:
      "Starting implementation. I'll follow the plan exactly and mark tasks complete as I go.",
    systemPrompt: (artifactDir) => `You are in IMPLEMENTATION mode. Execute the approved plan.

CRITICAL RULES:
1. Read ${artifactDir}/plan.md if it exists and follow it exactly.
   If plan.md does not exist, this session began at the implementation phase — implement based on the task description provided in the chat messages.
2. Mark tasks complete in ${artifactDir}/plan.md as you finish them: - [ ] → - [x]
3. DO NOT deviate from the plan without asking
4. Run tests/typecheck if available
5. Stop and ask if you encounter issues not covered by the plan

WORKFLOW:
1. Read ${artifactDir}/plan.md (if it exists)
2. Execute each task in order
3. Update ${artifactDir}/plan.md to mark tasks complete
4. Continue until all tasks are done

When complete, summarize what was done and any follow-up tasks.`,
  },
};

export function getPhaseConfig(
  phase: Phase,
  artifactDir: string,
  userPermissionMode?: UserPermissionMode,
  customSystemPrompt?: string
): PhaseConfig {
  const template = phaseConfigTemplates[phase];

  // If a custom prompt is provided, substitute the {{artifactDir}} placeholder.
  // Otherwise use the default template function (existing behaviour).
  const systemPrompt =
    customSystemPrompt !== undefined
      ? customSystemPrompt.replace(/\{\{artifactDir\}\}/g, artifactDir)
      : template.systemPrompt(artifactDir);

  const config: PhaseConfig = {
    systemPrompt,
    tools: template.tools,
    permissionMode: template.permissionMode,
    initialMessage: template.initialMessage,
  };
  if (phase === "implement" && userPermissionMode) {
    config.permissionMode = userPermissionMode;
  }
  return config;
}

/**
 * Returns the default system prompt for a phase with "{{artifactDir}}" as a
 * literal placeholder — the same format used when storing a custom prompt in
 * the settings DB. Used by the Settings UI to display the default text.
 */
export function getDefaultSystemPromptTemplate(phase: Phase): string {
  return phaseConfigTemplates[phase].systemPrompt("{{artifactDir}}");
}

export function getPhaseInitialMessage(phase: Phase): string {
  return phaseConfigTemplates[phase].initialMessage;
}

export function getNextPhase(phase: Phase): Phase | null {
  const transitions: Record<Phase, Phase | null> = {
    research: "plan",
    plan: "implement",
    implement: null,
  };
  return transitions[phase];
}

export function getArtifactFilename(phase: Phase): string {
  return phase === "research" ? "research.md" : "plan.md";
}