// import { combineReducers } from 'redux';

const REDUX_PATH_SEPARATOR = '/';

function normalizeNamespace(name) {
  return name.replace(/_(.)/, match => match[1].toUpperCase());
}

export default class ReduxGenerator {
  constructor(...id) {
    this._id = id;
  }

  sub(name) {
    return new ReduxGenerator(...this._id, name);
  }

  actionType(name) {
    return [...this._id, name]
      .join(REDUX_PATH_SEPARATOR);
  }

  actionObject(name, payload) {
    return {
      type: this.actionType(name),
      payload,
    };
  }

  selector(selector) {
    return (state, ...params) => {
      const selectedState = this._id
        .slice(1) // ignore root id
        .reduce((current, id) => current[id], state);

      return selector(selectedState, ...params);
    };
  }

  all({
    actions = {},
    selectors = {},
    reducers = {},
    initialState = null,
  }) {
    /*
    Descriptor = {
      someName: {
        params: {
          param1: (v) => typeof(value) === "string",
        },
        reducer(currentState, payload) {
          // ... do stuff
          return {
            ...currentState,
            ...newStateDiff,
          };
        },
      },
      // ...
    }
    */
    const retval = Object.entries(actions)
      .reduce((current, [
        name,
        {
          params = {},
          reducer,
        },
      ]) => {
        const id = this.actionType(name);

        // Validate params, they should all have a validator function as a value
        if (params) {
          const keysWithNonFunctionValidator = Object.keys(params)
            .filter(paramName => typeof (params[paramName]) !== 'function')
            .map(v => JSON.stringify(v));
          if (keysWithNonFunctionValidator.length > 0) {
            throw new Error(`Following params of ${JSON.stringify(id)} have a non-function value as validator: ${keysWithNonFunctionValidator.join(', ')}`);
          }
        }

        const target = {
          ...current,
          actions: {
            ...current.actions,
            [name]: (payload = {}) => {
              // Validate all payload values
              const err = Object.entries(payload)
                .map(([key, value]) => {
                  const validator = params[key];
                  if (validator === undefined || validator === null) {
                    console.warn(`${id}: extra argument ${JSON.stringify(key)}, ignoring`);
                    return undefined;
                  }
                  let result = validator(value);
                  // console.debug(`${id}: verifying ${JSON.stringify(key)} result:`, result);
                  switch (typeof result) {
                    case 'boolean': // validator returns either true on success or false on error
                      if (!result) {
                        result = new Error(`${JSON.stringify(key)}: invalid value: ${JSON.stringify(value)}`);
                      } else {
                        result = null;
                      }
                      break;
                    default: // error or string (or something else?)
                      if (result instanceof Error) { // modify message to include key
                        result.message = `${JSON.stringify(key)}: ${result.message}`;
                      } else { // use value as part of error reaosn
                        result = new Error(`${JSON.stringify(key)}: ${result}`);
                      }
                  }
                  Object.freeze(result);
                  return result;
                })
                .find(v => !!v);
              if (err) {
                throw err;
              }

              // Create action object
              return {
                type: id,
                payload,
              };
            },
          },
          actionTypes: {
            ...current.actionTypes,
            [name]: id,
          },
        };

        if (reducer) {
          target.reducers = {
            ...current.reducers,
            [name]: (state, { type, payload }) => {
              // Ignore non-matching actions
              if (type !== id) {
                // console.debug(`${type}: skipping action-mismatching reducer`, { state, payload });
                return state;
              }

              // Call original reducer with our payload
              // console.debug(`${type}: action-matched reducer called`, { state, payload });
              const result = reducer(state, payload);
              // console.debug(' =>', result);
              return result;
            },
          };
        }

        return target;
      }, {
        actions: {},
        actionTypes: {},
        reducers: Object.entries(reducers)
          .reduce((current, [name, reducer]) => ({
            [name]: (state, ...args) => {
              // console.debug(`${this._id.join('/', `reducer:${name}`)}: called`, { state, args });
              const result = reducer(state, ...args);
              // console.debug(' =>', result);
              return result;
            },
          }), {}),
        selectors: {},
      });

    retval.selectors = Object.entries(selectors)
      .reduce((current, [name, selector]) => ({
        ...current,
        [name]: (state, ...args) => {
          const namespaceState = this._id
            .slice(1) // ignore root id
            .map(normalizeNamespace)
            .reduce(
              (currentState, namespaceName) =>
                currentState[namespaceName], state);
          // console.debug(`${[...this._id, `selector:${name}`].join('/')}: called`, { state: namespaceState, args });
          const result = selector(namespaceState, ...args);
          // console.debug(' =>', result);
          return result;
        },
      }), selectors);

    retval.reducer = (state, ...args) => {
      // console.debug(`${this._id.join('/')}: combined reducer called`, { state, args });

      if (state === undefined) {
        // console.debug(`${this._id.join('/')}: undefined state passed to reducer`, { state, args });
        const result = initialState;
        // console.debug(' =>', result);
        return result;
      }

      // not using combineReducers here as we want all reducers to act on the same namespace

      if (retval.reducers) {
        return Object.values(retval.reducers)
          .filter(value => typeof (value) === 'function')
          .reduce(
            (current, reducer) => reducer(current, ...args),
            state,
          );
      }

      // console.debug(`${this._id.join('/')}: no reducers for this namespace, skipping`);
      return state;
    };

    // if (initialState) {
    //   retval.initialState = initialState;
    // }

    // console.debug('generated redux module:', retval);
    return retval;
  }
}