import { CODEX_PERMISSION_MODES } from '@hapi/protocol/modes';
import type { CodexPermissionMode } from '@hapi/protocol/types';
import type { ReasoningEffort } from '../appServerTypes';
import type { CodexPersonality, EnhancedMode } from '../loop';
import type { SlashCommand } from '@/modules/common/slashCommands';
import { parseReasoningEffortValue } from './reasoningEffort';

export const MAX_CODEX_GOAL_OBJECTIVE_CHARS = 4_000;

const CODEX_PERSONALITIES = ['friendly', 'pragmatic', 'none'] as const satisfies readonly CodexPersonality[];

const UNSUPPORTED_CODEX_BUILTIN_COMMANDS = new Set([
    'compat',
    'diff',
    'init',
    'login',
    'logout',
    'mcp',
    'new',
    'prompts',
    'quit',
    'redo',
    'review',
    'undo'
]);

export type CodexSlashResolution =
    | { kind: 'passthrough' }
    | {
        kind: 'handled';
        message: string;
        updates?: {
            collaborationMode?: EnhancedMode['collaborationMode'];
            permissionMode?: CodexPermissionMode;
            model?: string | null;
            modelReasoningEffort?: ReasoningEffort | null;
            serviceTier?: string | null;
            proactiveMultiAgent?: boolean;
            personality?: CodexPersonality;
        };
    }
    | {
        kind: 'replace';
        text: string;
        message?: string;
        updates?: {
            collaborationMode?: EnhancedMode['collaborationMode'];
            permissionMode?: CodexPermissionMode;
            model?: string | null;
            modelReasoningEffort?: ReasoningEffort | null;
            serviceTier?: string | null;
            proactiveMultiAgent?: boolean;
            personality?: CodexPersonality;
        };
    }
    | {
        kind: 'goal';
        action: 'show' | 'set' | 'pause' | 'resume' | 'clear';
        objective?: string;
        message?: string;
    };

export function resolveCodexSlashCommand(
    text: string,
    state: {
        commands?: readonly SlashCommand[];
        permissionMode: CodexPermissionMode;
        collaborationMode: EnhancedMode['collaborationMode'];
        model?: string;
        modelReasoningEffort?: ReasoningEffort;
        serviceTier?: string | null;
        proactiveMultiAgent?: boolean;
        personality?: CodexPersonality;
    }
): CodexSlashResolution {
    const match = /^\s*\/([a-z0-9:_-]+)(?:\s+([\s\S]*))?$/i.exec(text);
    if (!match) return { kind: 'passthrough' };

    const command = match[1]?.toLowerCase();
    const rest = match[2]?.trim() ?? '';
    if (!command) return { kind: 'passthrough' };

    const custom = state.commands?.find((candidate) =>
        candidate.source !== 'builtin' && candidate.name.toLowerCase() === command
    );
    if (custom?.content) {
        return {
            kind: 'replace',
            text: rest ? `${custom.content}\n\nUser arguments: ${rest}` : custom.content,
            message: `Expanded /${custom.name}`
        };
    }

    if (command === 'plan') {
        const lowerRest = rest.toLowerCase();
        if (lowerRest === 'off' || lowerRest === 'default' || lowerRest === 'exit' || lowerRest === 'disable') {
            return {
                kind: 'handled',
                message: 'Codex plan mode disabled',
                updates: { collaborationMode: 'default' }
            };
        }
        if (rest) {
            return {
                kind: 'replace',
                text: rest,
                message: 'Codex plan mode enabled',
                updates: { collaborationMode: 'plan' }
            };
        }
        return {
            kind: 'handled',
            message: 'Codex plan mode enabled',
            updates: { collaborationMode: 'plan' }
        };
    }

    if (command === 'agent') {
        const value = rest.toLowerCase();
        if (value === 'status') {
            return {
                kind: 'handled',
                message: `Codex proactive multi-agent mode: ${state.proactiveMultiAgent ? 'on' : 'off'}`
            };
        }
        if (value && !['on', 'enable', 'enabled', 'off', 'disable', 'disabled'].includes(value)) {
            return {
                kind: 'handled',
                message: 'Usage: /agent [on|off|status]'
            };
        }
        const enabled = value
            ? ['on', 'enable', 'enabled'].includes(value)
            : !state.proactiveMultiAgent;
        return {
            kind: 'handled',
            message: `Codex proactive multi-agent mode ${enabled ? 'enabled' : 'disabled'}`,
            updates: { proactiveMultiAgent: enabled }
        };
    }

    if (command === 'goal') {
        const lowerRest = rest.toLowerCase();
        if (!rest) {
            return { kind: 'goal', action: 'show' };
        }
        if (lowerRest === 'clear') {
            return { kind: 'goal', action: 'clear' };
        }
        if (lowerRest === 'pause') {
            return { kind: 'goal', action: 'pause' };
        }
        if (lowerRest === 'resume') {
            return { kind: 'goal', action: 'resume' };
        }
        const objective = rest.trim();
        if (!objective) {
            return {
                kind: 'handled',
                message: 'Goal objective must not be empty.'
            };
        }
        if ([...objective].length > MAX_CODEX_GOAL_OBJECTIVE_CHARS) {
            return {
                kind: 'handled',
                message: `Goal objective must be at most ${MAX_CODEX_GOAL_OBJECTIVE_CHARS} characters.`
            };
        }
        return {
            kind: 'goal',
            action: 'set',
            objective
        };
    }

    if (command === 'default' || command === 'execute') {
        return {
            kind: 'handled',
            message: 'Codex collaboration mode: default',
            updates: { collaborationMode: 'default' }
        };
    }

    if (command === 'status') {
        return {
            kind: 'handled',
            message: [
                '**Codex status**',
                '',
                `- permission: \`${state.permissionMode}\``,
                `- collaboration: \`${state.collaborationMode}\``,
                `- model: \`${state.model ?? 'auto'}\``,
                `- reasoning: \`${state.modelReasoningEffort ?? 'default'}\``,
                `- personality: \`${state.personality ?? 'unset'}\``
            ].join('\n')
        };
    }

    if (command === 'personality') {
        if (!rest) {
            return {
                kind: 'handled',
                message: `Codex personality: ${state.personality ?? 'unset (Codex config / thread sticky)'}`
            };
        }
        // turn/start.personality sticks for subsequent turns; omitting later does not
        // restore config.toml. Only explicit friendly|pragmatic|none are valid.
        if (rest === 'default' || rest === 'auto' || rest === 'clear') {
            return {
                kind: 'handled',
                message: 'Codex personality is sticky on the thread; set friendly, pragmatic, or none (cannot restore config.toml by clearing)'
            };
        }
        if (!(CODEX_PERSONALITIES as readonly string[]).includes(rest)) {
            return {
                kind: 'handled',
                message: `Unknown Codex personality: ${rest}`
            };
        }
        return {
            kind: 'handled',
            message: `Codex personality set to ${rest}`,
            updates: { personality: rest as CodexPersonality }
        };
    }

    if (command === 'model') {
        if (!rest) {
            return { kind: 'handled', message: `Codex model: ${state.model ?? 'auto'}` };
        }
        const model = rest === 'auto' ? null : rest;
        return {
            kind: 'handled',
            message: `Codex model set to ${model ?? 'auto'}`,
            updates: { model }
        };
    }

    if (command === 'reasoning' || command === 'effort') {
        if (!rest) {
            return { kind: 'handled', message: `Codex reasoning effort: ${state.modelReasoningEffort ?? 'default'}` };
        }
        if (rest === 'default' || rest === 'auto') {
            return {
                kind: 'handled',
                message: 'Codex reasoning effort set to default',
                updates: { modelReasoningEffort: null }
            };
        }
        const effort = parseReasoningEffortValue(rest);
        return {
            kind: 'handled',
            message: `Codex reasoning effort set to ${effort}`,
            updates: { modelReasoningEffort: effort }
        };
    }

    if (command === 'fast') {
        const arg = rest.toLowerCase();
        if (arg === '' || arg === 'on') {
            return {
                kind: 'handled',
                message: 'Codex Fast mode enabled',
                updates: { serviceTier: 'fast' }
            };
        }
        if (arg === 'off') {
            return {
                kind: 'handled',
                message: 'Codex Fast mode disabled',
                updates: { serviceTier: 'standard' }
            };
        }
        if (arg === 'status') {
            const on = state.serviceTier === 'fast';
            return {
                kind: 'handled',
                message: `Codex Fast mode: ${on ? 'on' : 'off'}`
            };
        }
        return {
            kind: 'handled',
            message: 'Usage: /fast [on|off|status]'
        };
    }

    if (command === 'permissions' || command === 'permission') {
        if (!rest) {
            return { kind: 'handled', message: `Codex permission mode: ${state.permissionMode}` };
        }
        if (!(CODEX_PERMISSION_MODES as readonly string[]).includes(rest)) {
            return {
                kind: 'handled',
                message: `Unknown Codex permission mode: ${rest}`
            };
        }
        return {
            kind: 'handled',
            message: `Codex permission mode set to ${rest}`,
            updates: { permissionMode: rest as CodexPermissionMode }
        };
    }

    if (command === 'help') {
        return {
            kind: 'handled',
            message: [
                '**Supported Codex slash commands**',
                '',
                '- `/plan [prompt]` — enable plan mode, optionally send prompt',
                '- `/plan off` — return to default mode',
                '- `/goal [objective]` — set or view the persistent goal',
                '- `/goal pause|resume|clear` — update the current goal',
                '- `/clear` — reset current Codex thread context',
                '- `/compact` — compact current Codex thread context',
                '- `/status` — show current Codex session config',
                '- `/model [name|auto]` — show or set model',
                '- `/reasoning [level|default]` — show or set reasoning effort',
                '- `/personality [friendly|pragmatic|none]` — show or set response style (sticky on thread)',
                '- `/fast [on|off|status]` — toggle Fast mode (GPT-5.5 / GPT-5.4, ChatGPT login)',
                '- `/permissions [default|read-only|safe-yolo|yolo]` — show or set permission mode',
                '',
                'Custom `/commands` from `.codex/prompts` are expanded before sending.'
            ].join('\n')
        };
    }

    if (UNSUPPORTED_CODEX_BUILTIN_COMMANDS.has(command)) {
        return {
            kind: 'handled',
            message: `/${command} is a Codex CLI command that is not supported in HAPI sessions yet.`
        };
    }

    return { kind: 'passthrough' };
}